Android 使用ContentProvider扫描手机中的图片，仿微信显示本地图片效果

转载：http://blog.csdn.net/xiaanming/article/details/18730223

写这篇文章之前，先简单说几句，首先是先恭喜下自己获得了2013年的博客之星称号，很意外也很开心，自己是从2013年开始写博客，那时候也不知道怎么写，我从小就不喜欢写日记，作文什么的，所以刚开始都是贴代码，也没有人看，后面慢慢的，写的文章被推荐博客首页和CSDN首页（这里也要小小的感谢下小编MM），访问量逐渐的多了起来，有更多的人看我的文章，这也使自己有了继续写文章的动力，也希望我写的东西对大家有点帮助吧，在2014年我会继续在CSDN上面写博客，然后是感谢博客之星给我投票支持我的朋友们，谢谢你们支持我的每一票，最后就是2014春节马上就到了，提前祝福大家新年快乐，工作顺利，事事顺心！

回到主题，之前群里面有朋友问我，有没有关于本地图片选择的Demo，类似微信的效果，他说网上没有这方面的Demo，问我能不能写一篇关于这个效果的Demo，于是我研究了下微信的本地图片选择的Demo，自己仿照的写了下分享给大家，希望对以后有这样子需求的朋友有一点帮助吧，主要使用的是ContentProvider扫描手机中的图片，并用GridView将图片显示出来，关于GridView和ListView显示图片的问题，一直是一个很头疼的问题，因为我们手机的内存有限，手机给每个应用程序分配的内存也有限，所以图片多的情况下很容易伴随着OOM的发生，不过现在也有很多的开源的图片显示框架，对显示很多图片进行了优化，大家有兴趣的可以去了解了解，今天我的这篇文章使用的是LruCache这个类（之前写了一篇使用LruCache加载网络图片的Android 异步加载图片，使用LruCache和SD卡或手机缓存，效果非常的流畅）以及对图片进行相对应的裁剪，这样也可以尽量的避免OOM的发生，我们先看下微信的效果吧

接下来我们就来实现这些效果吧，首先我们新建一个项目，取名ImageScan

首先我们先看第一个界面吧，使用将手机中的图片扫描出来，然后根据图片的所在的文件夹将其分类出来，并显示所在文件夹里面的一张图片和文件夹中图片个数，我们根据界面元素（文件夹名，文件夹图片个数，文件夹中的一张图片）使用一个实体对象ImageBean来封装这三个属性

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- <span class="keyword">package</span> com.example.imagescan;

- 
- <span class="comment">/**</span>

- <span class="comment"> * GridView的每个item的数据对象</span>

- <span class="comment"> * </span>

- <span class="comment"> * @author len</span>

- <span class="comment"> *</span>

- <span class="comment"> */</span>

- <span class="keyword">public</span> <span class="keyword">class</span> ImageBean{

- <span class="comment">/**</span>

- <span class="comment">     * 文件夹的第一张图片路径</span>

- <span class="comment">     */</span>

- <span class="keyword">private</span> String topImagePath;

- <span class="comment">/**</span>

- <span class="comment">     * 文件夹名</span>

- <span class="comment">     */</span>

- <span class="keyword">private</span> String folderName;

- <span class="comment">/**</span>

- <span class="comment">     * 文件夹中的图片数</span>

- <span class="comment">     */</span>

- <span class="keyword">private</span> <span class="keyword">int</span> imageCounts;

- 
- <span class="keyword">public</span> String getTopImagePath() {

- <span class="keyword">return</span> topImagePath;

- }

- <span class="keyword">public</span> <span class="keyword">void</span> setTopImagePath(String topImagePath) {

- <span class="keyword">this</span>.topImagePath = topImagePath;

- }

- <span class="keyword">public</span> String getFolderName() {

- <span class="keyword">return</span> folderName;

- }

- <span class="keyword">public</span> <span class="keyword">void</span> setFolderName(String folderName) {

- <span class="keyword">this</span>.folderName = folderName;

- }

- <span class="keyword">public</span> <span class="keyword">int</span> getImageCounts() {

- <span class="keyword">return</span> imageCounts;

- }

- <span class="keyword">public</span> <span class="keyword">void</span> setImageCounts(<span class="keyword">int</span> imageCounts) {

- <span class="keyword">this</span>.imageCounts = imageCounts;

- }

- 
- }

接下来就是主界面的布局啦，上面的导航栏我没有加进去，只有下面的GridView，所以说主界面布局中只有一个GridView

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- <span class="tag"><</span><span class="tag-name">RelativeLayout</span> <span class="attribute">xmlns:android</span>=<span class="attribute-value">&#8220;http://schemas.android.com/apk/res/android&#8221;</span>

- <span class="attribute">xmlns:tools</span>=<span class="attribute-value">&#8220;http://schemas.android.com/tools&#8221;</span>

- <span class="attribute">android:layout_width</span>=<span class="attribute-value">&#8220;match_parent&#8221;</span>

- <span class="attribute">android:layout_height</span>=<span class="attribute-value">&#8220;match_parent&#8221;</span> <span class="tag">></span>

- 
- <span class="tag"><</span><span class="tag-name">GridView</span>

- <span class="attribute">android:id</span>=<span class="attribute-value">&#8220;@+id/main_grid&#8221;</span>

- <span class="attribute">android:layout_width</span>=<span class="attribute-value">&#8220;match_parent&#8221;</span>

- <span class="attribute">android:layout_height</span>=<span class="attribute-value">&#8220;match_parent&#8221;</span>

- <span class="attribute">android:listSelector</span>=<span class="attribute-value">&#8220;@android:color/transparent&#8221;</span>

- <span class="attribute">android:cacheColorHint</span>=<span class="attribute-value">&#8220;@android:color/transparent&#8221;</span>

- <span class="attribute">android:stretchMode</span>=<span class="attribute-value">&#8220;columnWidth&#8221;</span>

- <span class="attribute">android:horizontalSpacing</span>=<span class="attribute-value">&#8220;20dip&#8221;</span>

- <span class="attribute">android:gravity</span>=<span class="attribute-value">&#8220;center&#8221;</span>

- <span class="attribute">android:verticalSpacing</span>=<span class="attribute-value">&#8220;20dip&#8221;</span>

- <span class="attribute">android:columnWidth</span>=<span class="attribute-value">&#8220;90dip&#8221;</span>

- <span class="attribute">android:numColumns</span>=<span class="attribute-value">&#8220;2&#8221;</span> <span class="tag">></span>

- <span class="tag"></</span><span class="tag-name">GridView</span><span class="tag">></span>

- 
- <span class="tag"></</span><span class="tag-name">RelativeLayout</span><span class="tag">></span>

接下来就是GridView的Item的布局，看上面的图也行你会认为他的效果是2张图片添加的效果，其实不是，后面的叠加效果只是一张背景图片而已，代码先贴上来

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- <span class="tag"><?</span><span class="tag-name">xml</span> <span class="attribute">version</span>=<span class="attribute-value">&#8220;1.0&#8221;</span> <span class="attribute">encoding</span>=<span class="attribute-value">&#8220;UTF-8&#8221;</span><span class="tag">?></span>

- <span class="tag"><</span><span class="tag-name">RelativeLayout</span> <span class="attribute">xmlns:android</span>=<span class="attribute-value">&#8220;http://schemas.android.com/apk/res/android&#8221;</span>

- <span class="attribute">android:layout_width</span>=<span class="attribute-value">&#8220;fill_parent&#8221;</span>

- <span class="attribute">android:layout_height</span>=<span class="attribute-value">&#8220;wrap_content&#8221;</span> <span class="tag">></span>

- 
- <span class="tag"><</span><span class="tag-name">FrameLayout</span>

- <span class="attribute">android:id</span>=<span class="attribute-value">&#8220;@+id/framelayout&#8221;</span>

- <span class="attribute">android:layout_width</span>=<span class="attribute-value">&#8220;fill_parent&#8221;</span>

- <span class="attribute">android:layout_height</span>=<span class="attribute-value">&#8220;wrap_content&#8221;</span> <span class="tag">></span>

- 
- <span class="tag"><</span><span class="tag-name">com.example.imagescan.MyImageView</span>

- <span class="attribute">android:id</span>=<span class="attribute-value">&#8220;@+id/group_image&#8221;</span>

- <span class="attribute">android:background</span>=<span class="attribute-value">&#8220;@drawable/albums_bg&#8221;</span>

- <span class="attribute">android:src</span>=<span class="attribute-value">&#8220;@drawable/friends_sends_pictures_no&#8221;</span>

- <span class="attribute">android:paddingLeft</span>=<span class="attribute-value">&#8220;20dip&#8221;</span>

- <span class="attribute">android:paddingRight</span>=<span class="attribute-value">&#8220;20dip&#8221;</span>

- <span class="attribute">android:paddingTop</span>=<span class="attribute-value">&#8220;18dip&#8221;</span>

- <span class="attribute">android:paddingBottom</span>=<span class="attribute-value">&#8220;30dip&#8221;</span>

- <span class="attribute">android:scaleType</span>=<span class="attribute-value">&#8220;fitXY&#8221;</span>

- <span class="attribute">android:layout_width</span>=<span class="attribute-value">&#8220;fill_parent&#8221;</span>

- <span class="attribute">android:layout_height</span>=<span class="attribute-value">&#8220;150dip&#8221;</span> <span class="tag">/></span>

- 
- <span class="tag"><</span><span class="tag-name">TextView</span>

- <span class="attribute">android:id</span>=<span class="attribute-value">&#8220;@+id/group_count&#8221;</span>

- <span class="attribute">android:layout_width</span>=<span class="attribute-value">&#8220;wrap_content&#8221;</span>

- <span class="attribute">android:layout_height</span>=<span class="attribute-value">&#8220;wrap_content&#8221;</span>

- <span class="attribute">android:background</span>=<span class="attribute-value">&#8220;@drawable/albums_icon_bg&#8221;</span>

- <span class="attribute">android:gravity</span>=<span class="attribute-value">&#8220;center&#8221;</span>

- <span class="attribute">android:layout_marginBottom</span>=<span class="attribute-value">&#8220;10dip&#8221;</span>

- <span class="attribute">android:text</span>=<span class="attribute-value">&#8220;5&#8221;</span>

- <span class="attribute">android:layout_gravity</span>=<span class="attribute-value">&#8220;bottom|center_horizontal&#8221;</span> <span class="tag">/></span>

- <span class="tag"></</span><span class="tag-name">FrameLayout</span><span class="tag">></span>

- 
- <span class="tag"><</span><span class="tag-name">TextView</span>

- <span class="attribute">android:id</span>=<span class="attribute-value">&#8220;@+id/group_title&#8221;</span>

- <span class="attribute">android:layout_width</span>=<span class="attribute-value">&#8220;fill_parent&#8221;</span>

- <span class="attribute">android:layout_height</span>=<span class="attribute-value">&#8220;wrap_content&#8221;</span>

- <span class="attribute">android:gravity</span>=<span class="attribute-value">&#8220;center&#8221;</span>

- <span class="attribute">android:layout_below</span>=<span class="attribute-value">&#8220;@id/framelayout&#8221;</span>

- <span class="attribute">android:layout_centerHorizontal</span>=<span class="attribute-value">&#8220;true&#8221;</span>

- <span class="attribute">android:ellipsize</span>=<span class="attribute-value">&#8220;end&#8221;</span>

- <span class="attribute">android:singleLine</span>=<span class="attribute-value">&#8220;true&#8221;</span>

- <span class="attribute">android:text</span>=<span class="attribute-value">&#8220;Camera&#8221;</span>

- <span class="attribute">android:textSize</span>=<span class="attribute-value">&#8220;16sp&#8221;</span> <span class="tag">/></span>

- 
- <span class="tag"></</span><span class="tag-name">RelativeLayout</span><span class="tag">></span>

看到上面的布局代码，也行你已经发现了，上面使用的是自定义的MyImageView，我先不说这个自定义MyImageView的作用，待会再给大家说，我们继续看代码

第一个界面的主要代码

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- <span class="keyword">package</span> com.example.imagescan;

- 
- <span class="keyword">import</span> java.io.File;

- <span class="keyword">import</span> java.util.ArrayList;

- <span class="keyword">import</span> java.util.HashMap;

- <span class="keyword">import</span> java.util.Iterator;

- <span class="keyword">import</span> java.util.List;

- <span class="keyword">import</span> java.util.Map;

- 
- <span class="keyword">import</span> android.app.Activity;

- <span class="keyword">import</span> android.app.ProgressDialog;

- <span class="keyword">import</span> android.content.ContentResolver;

- <span class="keyword">import</span> android.content.Intent;

- <span class="keyword">import</span> android.database.Cursor;

- <span class="keyword">import</span> android.net.Uri;

- <span class="keyword">import</span> android.os.Bundle;

- <span class="keyword">import</span> android.os.Handler;

- <span class="keyword">import</span> android.os.Message;

- <span class="keyword">import</span> android.provider.MediaStore;

- <span class="keyword">import</span> android.view.View;

- <span class="keyword">import</span> android.widget.AdapterView;

- <span class="keyword">import</span> android.widget.AdapterView.OnItemClickListener;

- <span class="keyword">import</span> android.widget.GridView;

- <span class="comment">/**</span>

- <span class="comment"> * @blog http://blog.csdn.net/xiaanming</span>

- <span class="comment"> * </span>

- <span class="comment"> * @author xiaanming</span>

- <span class="comment"> * </span>

- <span class="comment"> *</span>

- <span class="comment"> */</span>

- <span class="keyword">public</span> <span class="keyword">class</span> MainActivity <span class="keyword">extends</span> Activity {

- <span class="keyword">private</span> HashMap<String, List<String>> mGruopMap = <span class="keyword">new</span> HashMap<String, List<String>>();

- <span class="keyword">private</span> List<ImageBean> list = <span class="keyword">new</span> ArrayList<ImageBean>();

- <span class="keyword">private</span> <span class="keyword">final</span> <span class="keyword">static</span> <span class="keyword">int</span> SCAN_OK = <span class="number">1</span>;

- <span class="keyword">private</span> ProgressDialog mProgressDialog;

- <span class="keyword">private</span> GroupAdapter adapter;

- <span class="keyword">private</span> GridView mGroupGridView;

- 
- <span class="keyword">private</span> Handler mHandler = <span class="keyword">new</span> Handler(){

- 
- <span class="annotation">@Override</span>

- <span class="keyword">public</span> <span class="keyword">void</span> handleMessage(Message msg) {

- <span class="keyword">super</span>.handleMessage(msg);

- <span class="keyword">switch</span> (msg.what) {

- <span class="keyword">case</span> SCAN_OK:

- <span class="comment">//关闭进度条</span>

- mProgressDialog.dismiss();

- 
- adapter = <span class="keyword">new</span> GroupAdapter(MainActivity.<span class="keyword">this</span>, list = subGroupOfImage(mGruopMap), mGroupGridView);

- mGroupGridView.setAdapter(adapter);

- <span class="keyword">break</span>;

- }

- }

- 
- };

- 
- <span class="annotation">@Override</span>

- <span class="keyword">protected</span> <span class="keyword">void</span> onCreate(Bundle savedInstanceState) {

- <span class="keyword">super</span>.onCreate(savedInstanceState);

- setContentView(R.layout.activity_main);

- 
- mGroupGridView = (GridView) findViewById(R.id.main_grid);

- 
- getImages();

- 
- mGroupGridView.setOnItemClickListener(<span class="keyword">new</span> OnItemClickListener() {

- 
- <span class="annotation">@Override</span>

- <span class="keyword">public</span> <span class="keyword">void</span> onItemClick(AdapterView<?> parent, View view,

- <span class="keyword">int</span> position, <span class="keyword">long</span> id) {

- List<String> childList = mGruopMap.get(list.get(position).getFolderName());

- 
- Intent mIntent = <span class="keyword">new</span> Intent(MainActivity.<span class="keyword">this</span>, ShowImageActivity.<span class="keyword">class</span>);

- mIntent.putStringArrayListExtra(<span class="string">&#8220;data&#8221;</span>, (ArrayList<String>)childList);

- startActivity(mIntent);

- 
- }

- });

- 
- }

- 
- 
- <span class="comment">/**</span>

- <span class="comment">     * 利用ContentProvider扫描手机中的图片，此方法在运行在子线程中</span>

- <span class="comment">     */</span>

- <span class="keyword">private</span> <span class="keyword">void</span> getImages() {

- <span class="comment">//显示进度条</span>

- mProgressDialog = ProgressDialog.show(<span class="keyword">this</span>, <span class="keyword">null</span>, <span class="string">&#8220;正在加载&#8230;&#8221;</span>);

- 
- <span class="keyword">new</span> Thread(<span class="keyword">new</span> Runnable() {

- 
- <span class="annotation">@Override</span>

- <span class="keyword">public</span> <span class="keyword">void</span> run() {

- Uri mImageUri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;

- ContentResolver mContentResolver = MainActivity.<span class="keyword">this</span>.getContentResolver();

- 
- <span class="comment">//只查询jpeg和png的图片</span>

- Cursor mCursor = mContentResolver.query(mImageUri, <span class="keyword">null</span>,

- MediaStore.Images.Media.MIME_TYPE + <span class="string">&#8220;=? or &#8220;</span>

- + MediaStore.Images.Media.MIME_TYPE + <span class="string">&#8220;=?&#8221;</span>,

- <span class="keyword">new</span> String[] { <span class="string">&#8220;image/jpeg&#8221;</span>, <span class="string">&#8220;image/png&#8221;</span> }, MediaStore.Images.Media.DATE_MODIFIED);

- 
- <span class="keyword">if</span>(mCursor == <span class="keyword">null</span>){

- <span class="keyword">return</span>;

- }

- 
- <span class="keyword">while</span> (mCursor.moveToNext()) {

- <span class="comment">//获取图片的路径</span>

- String path = mCursor.getString(mCursor

- .getColumnIndex(MediaStore.Images.Media.DATA));

- 
- <span class="comment">//获取该图片的父路径名</span>

- String parentName = <span class="keyword">new</span> File(path).getParentFile().getName();

- 
- 
- <span class="comment">//根据父路径名将图片放入到mGruopMap中</span>

- <span class="keyword">if</span> (!mGruopMap.containsKey(parentName)) {

- List<String> chileList = <span class="keyword">new</span> ArrayList<String>();

- chileList.add(path);

- mGruopMap.put(parentName, chileList);

- } <span class="keyword">else</span> {

- mGruopMap.get(parentName).add(path);

- }

- }

- 
- <span class="comment">//通知Handler扫描图片完成</span>

- mHandler.sendEmptyMessage(SCAN_OK);

- mCursor.close();

- }

- }).start();

- 
- }

- 
- 
- <span class="comment">/**</span>

- <span class="comment">     * 组装分组界面GridView的数据源，因为我们扫描手机的时候将图片信息放在HashMap中</span>

- <span class="comment">     * 所以需要遍历HashMap将数据组装成List</span>

- <span class="comment">     * </span>

- <span class="comment">     * @param mGruopMap</span>

- <span class="comment">     * @return</span>

- <span class="comment">     */</span>

- <span class="keyword">private</span> List<ImageBean> subGroupOfImage(HashMap<String, List<String>> mGruopMap){

- <span class="keyword">if</span>(mGruopMap.size() == <span class="number"></span>){

- <span class="keyword">return</span> <span class="keyword">null</span>;

- }

- List<ImageBean> list = <span class="keyword">new</span> ArrayList<ImageBean>();

- 
- Iterator<Map.Entry<String, List<String>>> it = mGruopMap.entrySet().iterator();

- <span class="keyword">while</span> (it.hasNext()) {

- Map.Entry<String, List<String>> entry = it.next();

- ImageBean mImageBean = <span class="keyword">new</span> ImageBean();

- String key = entry.getKey();

- List<String> value = entry.getValue();

- 
- mImageBean.setFolderName(key);

- mImageBean.setImageCounts(value.size());

- mImageBean.setTopImagePath(value.get(<span class="number"></span>));<span class="comment">//获取该组的第一张图片</span>

- 
- list.add(mImageBean);

- }

- 
- <span class="keyword">return</span> list;

- 
- }

- 
- 
- }

首先看getImages()这个方法，该方法是使用ContentProvider将手机中的图片扫描出来，我这里只扫描了手机的外部存储中的图片，由于手机中可能存在很多的图片，扫描图片又比较耗时，所以我们在这里开启了子线程去获取图片，扫描的图片都存放在Cursor中，我们先要将图片按照文件夹进行分类,我们使用了HashMap来进行分类并将结果存储到mGruopMap（Key是文件夹名，Value是文件夹中的图片路径的List）中，分类完了关闭Cursor并利用Handler来通知主线程
然后是subGroupOfImage()方法，改方法是将mGruopMap的数据组装到List中，在List中存放GridView中的每个item的数据对象ImageBean, 遍历HashMap对象，具体的逻辑看代码，之后就是给GridView设置Adapter。
设置item点击事件，点击文件夹跳转到展示文件夹图片的Activity, 我们需要传递每个文件夹中的图片的路径的集合

看GroupAdapter的代码之前，我们先看一个比较重要的类，本地图片加载器NativeImageLoader

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- <span class="keyword">package</span> com.example.imagescan;

- 
- <span class="keyword">import</span> java.util.concurrent.ExecutorService;

- <span class="keyword">import</span> java.util.concurrent.Executors;

- 
- <span class="keyword">import</span> android.graphics.Bitmap;

- <span class="keyword">import</span> android.graphics.BitmapFactory;

- <span class="keyword">import</span> android.graphics.Point;

- <span class="keyword">import</span> android.os.Handler;

- <span class="keyword">import</span> android.os.Message;

- <span class="keyword">import</span> android.support.v4.util.LruCache;

- 
- <span class="comment">/**</span>

- <span class="comment"> * 本地图片加载器,采用的是异步解析本地图片，单例模式利用getInstance()获取NativeImageLoader实例</span>

- <span class="comment"> * 调用loadNativeImage()方法加载本地图片，此类可作为一个加载本地图片的工具类</span>

- <span class="comment"> * </span>

- <span class="comment"> * @blog http://blog.csdn.net/xiaanming</span>

- <span class="comment"> * </span>

- <span class="comment"> * @author xiaanming</span>

- <span class="comment"> *</span>

- <span class="comment"> */</span>

- <span class="keyword">public</span> <span class="keyword">class</span> NativeImageLoader {

- <span class="keyword">private</span> LruCache<String, Bitmap> mMemoryCache;

- <span class="keyword">private</span> <span class="keyword">static</span> NativeImageLoader mInstance = <span class="keyword">new</span> NativeImageLoader();

- <span class="keyword">private</span> ExecutorService mImageThreadPool = Executors.newFixedThreadPool(<span class="number">1</span>);

- 
- 
- <span class="keyword">private</span> NativeImageLoader(){

- <span class="comment">//获取应用程序的最大内存</span>

- <span class="keyword">final</span> <span class="keyword">int</span> maxMemory = (<span class="keyword">int</span>) (Runtime.getRuntime().maxMemory() / <span class="number">1024</span>);

- 
- <span class="comment">//用最大内存的1/4来存储图片</span>

- <span class="keyword">final</span> <span class="keyword">int</span> cacheSize = maxMemory / <span class="number">4</span>;

- mMemoryCache = <span class="keyword">new</span> LruCache<String, Bitmap>(cacheSize) {

- 
- <span class="comment">//获取每张图片的大小</span>

- <span class="annotation">@Override</span>

- <span class="keyword">protected</span> <span class="keyword">int</span> sizeOf(String key, Bitmap bitmap) {

- <span class="keyword">return</span> bitmap.getRowBytes() * bitmap.getHeight() / <span class="number">1024</span>;

- }

- };

- }

- 
- <span class="comment">/**</span>

- <span class="comment">     * 通过此方法来获取NativeImageLoader的实例</span>

- <span class="comment">     * @return</span>

- <span class="comment">     */</span>

- <span class="keyword">public</span> <span class="keyword">static</span> NativeImageLoader getInstance(){

- <span class="keyword">return</span> mInstance;

- }

- 
- 
- <span class="comment">/**</span>

- <span class="comment">     * 加载本地图片，对图片不进行裁剪</span>

- <span class="comment">     * @param path</span>

- <span class="comment">     * @param mCallBack</span>

- <span class="comment">     * @return</span>

- <span class="comment">     */</span>

- <span class="keyword">public</span> Bitmap loadNativeImage(<span class="keyword">final</span> String path, <span class="keyword">final</span> NativeImageCallBack mCallBack){

- <span class="keyword">return</span> <span class="keyword">this</span>.loadNativeImage(path, <span class="keyword">null</span>, mCallBack);

- }

- 
- <span class="comment">/**</span>

- <span class="comment">     * 此方法来加载本地图片，这里的mPoint是用来封装ImageView的宽和高，我们会根据ImageView控件的大小来裁剪Bitmap</span>

- <span class="comment">     * 如果你不想裁剪图片，调用loadNativeImage(final String path, final NativeImageCallBack mCallBack)来加载</span>

- <span class="comment">     * @param path</span>

- <span class="comment">     * @param mPoint</span>

- <span class="comment">     * @param mCallBack</span>

- <span class="comment">     * @return</span>

- <span class="comment">     */</span>

- <span class="keyword">public</span> Bitmap loadNativeImage(<span class="keyword">final</span> String path, <span class="keyword">final</span> Point mPoint, <span class="keyword">final</span> NativeImageCallBack mCallBack){

- <span class="comment">//先获取内存中的Bitmap</span>

- Bitmap bitmap = getBitmapFromMemCache(path);

- 
- <span class="keyword">final</span> Handler mHander = <span class="keyword">new</span> Handler(){

- 
- <span class="annotation">@Override</span>

- <span class="keyword">public</span> <span class="keyword">void</span> handleMessage(Message msg) {

- <span class="keyword">super</span>.handleMessage(msg);

- mCallBack.onImageLoader((Bitmap)msg.obj, path);

- }

- 
- };

- 
- <span class="comment">//若该Bitmap不在内存缓存中，则启用线程去加载本地的图片，并将Bitmap加入到mMemoryCache中</span>

- <span class="keyword">if</span>(bitmap == <span class="keyword">null</span>){

- mImageThreadPool.execute(<span class="keyword">new</span> Runnable() {

- 
- <span class="annotation">@Override</span>

- <span class="keyword">public</span> <span class="keyword">void</span> run() {

- <span class="comment">//先获取图片的缩略图</span>

- Bitmap mBitmap = decodeThumbBitmapForFile(path, mPoint == <span class="keyword">null</span> ? <span class="number"></span>: mPoint.x, mPoint == <span class="keyword">null</span> ? <span class="number"></span>: mPoint.y);

- Message msg = mHander.obtainMessage();

- msg.obj = mBitmap;

- mHander.sendMessage(msg);

- 
- <span class="comment">//将图片加入到内存缓存</span>

- addBitmapToMemoryCache(path, mBitmap);

- }

- });

- }

- <span class="keyword">return</span> bitmap;

- 
- }

- 
- 
- 
- <span class="comment">/**</span>

- <span class="comment">     * 往内存缓存中添加Bitmap</span>

- <span class="comment">     * </span>

- <span class="comment">     * @param key</span>

- <span class="comment">     * @param bitmap</span>

- <span class="comment">     */</span>

- <span class="keyword">private</span> <span class="keyword">void</span> addBitmapToMemoryCache(String key, Bitmap bitmap) {

- <span class="keyword">if</span> (getBitmapFromMemCache(key) == <span class="keyword">null</span> && bitmap != <span class="keyword">null</span>) {

- mMemoryCache.put(key, bitmap);

- }

- }

- 
- <span class="comment">/**</span>

- <span class="comment">     * 根据key来获取内存中的图片</span>

- <span class="comment">     * @param key</span>

- <span class="comment">     * @return</span>

- <span class="comment">     */</span>

- <span class="keyword">private</span> Bitmap getBitmapFromMemCache(String key) {

- <span class="keyword">return</span> mMemoryCache.get(key);

- }

- 
- 
- <span class="comment">/**</span>

- <span class="comment">     * 根据View(主要是ImageView)的宽和高来获取图片的缩略图</span>

- <span class="comment">     * @param path</span>

- <span class="comment">     * @param viewWidth</span>

- <span class="comment">     * @param viewHeight</span>

- <span class="comment">     * @return</span>

- <span class="comment">     */</span>

- <span class="keyword">private</span> Bitmap decodeThumbBitmapForFile(String path, <span class="keyword">int</span> viewWidth, <span class="keyword">int</span> viewHeight){

- BitmapFactory.Options options = <span class="keyword">new</span> BitmapFactory.Options();

- <span class="comment">//设置为true,表示解析Bitmap对象，该对象不占内存</span>

- options.inJustDecodeBounds = <span class="keyword">true</span>;

- BitmapFactory.decodeFile(path, options);

- <span class="comment">//设置缩放比例</span>

- options.inSampleSize = computeScale(options, viewWidth, viewHeight);

- 
- <span class="comment">//设置为false,解析Bitmap对象加入到内存中</span>

- options.inJustDecodeBounds = <span class="keyword">false</span>;

- 
- <span class="keyword">return</span> BitmapFactory.decodeFile(path, options);

- }

- 
- 
- <span class="comment">/**</span>

- <span class="comment">     * 根据View(主要是ImageView)的宽和高来计算Bitmap缩放比例。默认不缩放</span>

- <span class="comment">     * @param options</span>

- <span class="comment">     * @param width</span>

- <span class="comment">     * @param height</span>

- <span class="comment">     */</span>

- <span class="keyword">private</span> <span class="keyword">int</span> computeScale(BitmapFactory.Options options, <span class="keyword">int</span> viewWidth, <span class="keyword">int</span> viewHeight){

- <span class="keyword">int</span> inSampleSize = <span class="number">1</span>;

- <span class="keyword">if</span>(viewWidth == <span class="number"></span> || viewWidth == <span class="number"></span>){

- <span class="keyword">return</span> inSampleSize;

- }

- <span class="keyword">int</span> bitmapWidth = options.outWidth;

- <span class="keyword">int</span> bitmapHeight = options.outHeight;

- 
- <span class="comment">//假如Bitmap的宽度或高度大于我们设定图片的View的宽高，则计算缩放比例</span>

- <span class="keyword">if</span>(bitmapWidth > viewWidth || bitmapHeight > viewWidth){

- <span class="keyword">int</span> widthScale = Math.round((<span class="keyword">float</span>) bitmapWidth / (<span class="keyword">float</span>) viewWidth);

- <span class="keyword">int</span> heightScale = Math.round((<span class="keyword">float</span>) bitmapHeight / (<span class="keyword">float</span>) viewWidth);

- 
- <span class="comment">//为了保证图片不缩放变形，我们取宽高比例最小的那个</span>

- inSampleSize = widthScale < heightScale ? widthScale : heightScale;

- }

- <span class="keyword">return</span> inSampleSize;

- }

- 
- 
- <span class="comment">/**</span>

- <span class="comment">     * 加载本地图片的回调接口</span>

- <span class="comment">     * </span>

- <span class="comment">     * @author xiaanming</span>

- <span class="comment">     *</span>

- <span class="comment">     */</span>

- <span class="keyword">public</span> <span class="keyword">interface</span> NativeImageCallBack{

- <span class="comment">/**</span>

- <span class="comment">         * 当子线程加载完了本地的图片，将Bitmap和图片路径回调在此方法中</span>

- <span class="comment">         * @param bitmap</span>

- <span class="comment">         * @param path</span>

- <span class="comment">         */</span>

- <span class="keyword">public</span> <span class="keyword">void</span> onImageLoader(Bitmap bitmap, String path);

- }

- }

该类是一个单例类，提供了本地图片加载，内存缓存，裁剪等逻辑，该类在加载本地图片的时候采用的是异步加载的方式，对于大图片的加载也是比较耗时的，所以采用子线程的方式去加载，对于图片的缓存机制使用的是LruCache，使用手机分配给应用程序内存的1/4用来缓存图片，除了使用LruCache缓存图片之外，还对图片进行了裁剪，举个很简单的例子，假如我们的控件大小是100 * 100，而我们的图片是400*400，我们加载这么大的图片需要很多的内存，所以我们采用了图片裁剪，根据控件的大小来确定图片的裁剪比例，从而减小内存的消耗，提高GridView滑动的流畅度，介绍里面几个比较重要的方法

computeScale()计算图片需要裁剪的比例，根据控件的大小和图片的大小确定比例，如果图片比控件大，我们就进行裁剪，否则不需要。
decodeThumbBitmapForFile()方法是根据计算好了图片裁剪的比例之后从文件中加载图片，我们先设置options.inJustDecodeBounds = true表示解析不占用内存，但是我们能获取图片的具体大小，利用computeScale()计算好比例，在将options.inJustDecodeBounds=false,再次解析Bitmap，这样子就对图片进行了裁剪。
loadNativeImage(final String path, final Point mPoint, final NativeImageCallBack mCallBack)我们在客户端只需要调用该方法就能获取到Bitmap对象，里面的具体逻辑是先判断内存缓存LruCache中是否存在该Bitmap，不存在就开启子线程去读取，为了方便管理加载本地图片线程，这里使用了线程池，池中只能容纳一个线程，读取完了本地图片先将Bitmap加入到LruCache中，保存的Key为图片路径，然后再使用Handler通知主线程图片加载好了，之后将Bitmap和路径回调到方法onImageLoader(Bitmap bitmap, String path)中，该方法的mPoint是用来封装控件的宽和高的对象
如果不对图片进行裁剪直接这个方法的重载方法loadNativeImage(final String path, final NativeImageCallBack mCallBack) 就行了，逻辑是一样的，只是这个方法不对图片进行裁剪

接下来就是GridView的Adapter类的代码

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- <span class="keyword">package</span> com.example.imagescan;

- 
- <span class="keyword">import</span> java.util.List;

- 
- <span class="keyword">import</span> android.content.Context;

- <span class="keyword">import</span> android.graphics.Bitmap;

- <span class="keyword">import</span> android.graphics.Point;

- <span class="keyword">import</span> android.view.LayoutInflater;

- <span class="keyword">import</span> android.view.View;

- <span class="keyword">import</span> android.view.ViewGroup;

- <span class="keyword">import</span> android.widget.BaseAdapter;

- <span class="keyword">import</span> android.widget.GridView;

- <span class="keyword">import</span> android.widget.ImageView;

- <span class="keyword">import</span> android.widget.TextView;

- 
- <span class="keyword">import</span> com.example.imagescan.MyImageView.OnMeasureListener;

- <span class="keyword">import</span> com.example.imagescan.NativeImageLoader.NativeImageCallBack;

- 
- <span class="keyword">public</span> <span class="keyword">class</span> GroupAdapter <span class="keyword">extends</span> BaseAdapter{

- <span class="keyword">private</span> List<ImageBean> list;

- <span class="keyword">private</span> Point mPoint = <span class="keyword">new</span> Point(<span class="number"></span>, <span class="number"></span>);<span class="comment">//用来封装ImageView的宽和高的对象</span>

- <span class="keyword">private</span> GridView mGridView;

- <span class="keyword">protected</span> LayoutInflater mInflater;

- 
- <span class="annotation">@Override</span>

- <span class="keyword">public</span> <span class="keyword">int</span> getCount() {

- <span class="keyword">return</span> list.size();

- }

- 
- <span class="annotation">@Override</span>

- <span class="keyword">public</span> Object getItem(<span class="keyword">int</span> position) {

- <span class="keyword">return</span> list.get(position);

- }

- 
- 
- <span class="annotation">@Override</span>

- <span class="keyword">public</span> <span class="keyword">long</span> getItemId(<span class="keyword">int</span> position) {

- <span class="keyword">return</span> position;

- }

- 
- <span class="keyword">public</span> GroupAdapter(Context context, List<ImageBean> list, GridView mGridView){

- <span class="keyword">this</span>.list = list;

- <span class="keyword">this</span>.mGridView = mGridView;

- mInflater = LayoutInflater.from(context);

- }

- 
- 
- <span class="annotation">@Override</span>

- <span class="keyword">public</span> View getView(<span class="keyword">int</span> position, View convertView, ViewGroup parent) {

- <span class="keyword">final</span> ViewHolder viewHolder;

- ImageBean mImageBean = list.get(position);

- String path = mImageBean.getTopImagePath();

- <span class="keyword">if</span>(convertView == <span class="keyword">null</span>){

- viewHolder = <span class="keyword">new</span> ViewHolder();

- convertView = mInflater.inflate(R.layout.grid_group_item, <span class="keyword">null</span>);

- viewHolder.mImageView = (MyImageView) convertView.findViewById(R.id.group_image);

- viewHolder.mTextViewTitle = (TextView) convertView.findViewById(R.id.group_title);

- viewHolder.mTextViewCounts = (TextView) convertView.findViewById(R.id.group_count);

- 
- <span class="comment">//用来监听ImageView的宽和高</span>

- viewHolder.mImageView.setOnMeasureListener(<span class="keyword">new</span> OnMeasureListener() {

- 
- <span class="annotation">@Override</span>

- <span class="keyword">public</span> <span class="keyword">void</span> onMeasureSize(<span class="keyword">int</span> width, <span class="keyword">int</span> height) {

- mPoint.set(width, height);

- }

- });

- 
- convertView.setTag(viewHolder);

- }<span class="keyword">else</span>{

- viewHolder = (ViewHolder) convertView.getTag();

- viewHolder.mImageView.setImageResource(R.drawable.friends_sends_pictures_no);

- }

- 
- viewHolder.mTextViewTitle.setText(mImageBean.getFolderName());

- viewHolder.mTextViewCounts.setText(Integer.toString(mImageBean.getImageCounts()));

- <span class="comment">//给ImageView设置路径Tag,这是异步加载图片的小技巧</span>

- viewHolder.mImageView.setTag(path);

- 
- 
- <span class="comment">//利用NativeImageLoader类加载本地图片</span>

- Bitmap bitmap = NativeImageLoader.getInstance().loadNativeImage(path, mPoint, <span class="keyword">new</span> NativeImageCallBack() {

- 
- <span class="annotation">@Override</span>

- <span class="keyword">public</span> <span class="keyword">void</span> onImageLoader(Bitmap bitmap, String path) {

- ImageView mImageView = (ImageView) mGridView.findViewWithTag(path);

- <span class="keyword">if</span>(bitmap != <span class="keyword">null</span> && mImageView != <span class="keyword">null</span>){

- mImageView.setImageBitmap(bitmap);

- }

- }

- });

- 
- <span class="keyword">if</span>(bitmap != <span class="keyword">null</span>){

- viewHolder.mImageView.setImageBitmap(bitmap);

- }<span class="keyword">else</span>{

- viewHolder.mImageView.setImageResource(R.drawable.friends_sends_pictures_no);

- }

- 
- 
- <span class="keyword">return</span> convertView;

- }

- 
- 
- 
- <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">class</span> ViewHolder{

- <span class="keyword">public</span> MyImageView mImageView;

- <span class="keyword">public</span> TextView mTextViewTitle;

- <span class="keyword">public</span> TextView mTextViewCounts;

- }

- 
- 
- }

首先我们将每个item的图片路径设置Tag到该ImageView上面，然后利用NativeImageLoader来加载本地图片，但是我们显示的图片的宽和高可能远大于GirdView item中ImageView的大小，于是为了节省内存，我们需要对图片进行裁剪，需要对图片裁剪我们利用loadNativeImage(final String path, final Point mPoint, final NativeImageCallBack mCallBack)方法,我们就必须要获取ImageView的宽和高了

但是我们想在getView()中获取ImageView的宽和高存在问题，在getView()里面刚开始显示item的时候利用ImageView.getWidth() 获取的都是0，为什么刚开始获取不到宽和高呢，因为我们使用LayoutInflater来将XML布局文件Inflater()成View的时候,View并没有显示在界面上面，表明并没有对View进行onMeasure(), onLayout(), onDraw()等操作，必须等到retrue convertView的时候，表示该item对应的View已经绘制在ListView的位置上了，此时才对item对应的View进行onMeasure(), onLayout(), onDraw()等操作，这时候才能获取到Item的宽和高，于是我想到了自定义ImageView，在onMeasure()中利用回调的模式主动通知我ImageView测量的宽和高，但是这有一个小小的问题，就是显示GridView的第一个item的时候，获取的宽和高还是0，第二个就能正常获取了，第一个宽和高为0，表示我们不对第一张图片进行裁剪而已，在效率上也没啥问题，不知道大家有没有好的方法，可以在getView()中获取Item中某个控件的宽和高。

自定义MyImageView的代码，我们只需要设置OnMeasureListener监听，当MyImageView测量完毕之后，就会将测量的宽和高回调到onMeasureSize()中，然后我们可以根据MyImageView的大小来裁剪图片

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    </embed>
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- <span class="keyword">package</span> com.example.imagescan;

- 
- <span class="keyword">import</span> android.content.Context;

- <span class="keyword">import</span> android.util.AttributeSet;

- <span class="keyword">import</span> android.widget.ImageView;

- 
- <span class="keyword">public</span> <span class="keyword">class</span> MyImageView <span class="keyword">extends</span> ImageView {

- <span class="keyword">private</span> OnMeasureListener onMeasureListener;

- 
- <span class="keyword">public</span> <span class="keyword">void</span> setOnMeasureListener(OnMeasureListener onMeasureListener) {

- <span class="keyword">this</span>.onMeasureListener = onMeasureListener;

- }

- 
- <span class="keyword">public</span> MyImageView(Context context, AttributeSet attrs) {

- <span class="keyword">super</span>(context, attrs);

- }

- 
- <span class="keyword">public</span> MyImageView(Context context, AttributeSet attrs, <span class="keyword">int</span> defStyle) {

- <span class="keyword">super</span>(context, attrs, defStyle);

- }

- 
- <span class="annotation">@Override</span>

- <span class="keyword">protected</span> <span class="keyword">void</span> onMeasure(<span class="keyword">int</span> widthMeasureSpec, <span class="keyword">int</span> heightMeasureSpec) {

- <span class="keyword">super</span>.onMeasure(widthMeasureSpec, heightMeasureSpec);

- 
- <span class="comment">//将图片测量的大小回调到onMeasureSize()方法中</span>

- <span class="keyword">if</span>(onMeasureListener != <span class="keyword">null</span>){

- onMeasureListener.onMeasureSize(getMeasuredWidth(), getMeasuredHeight());

- }

- }

- 
- <span class="keyword">public</span> <span class="keyword">interface</span> OnMeasureListener{

- <span class="keyword">public</span> <span class="keyword">void</span> onMeasureSize(<span class="keyword">int</span> width, <span class="keyword">int</span> height);

- }

- 
- }

上面这些代码就完成了第一个界面的功能了，接下来就是点击GridView的item跳转另一个界面来显示该文件夹下面的所有图片，功能跟第一个界面差不多，也是使用GridView来显示图片，第二个界面的布局代码我就不贴了，直接贴上界面的代码

  <div>
    <embed id="ZeroClipboardMovie_8" src="http://static.blog.csdn.net/scripts/ZeroClipboard/ZeroClipboard.swf" type="application/x-shockwave-flash" width="18" height="18" align="middle" name="ZeroClipboardMovie_8">
    </embed>
  </div>
</div>

- <span class="keyword">package</span> com.example.imagescan;

- 
- <span class="keyword">import</span> java.util.List;

- 
- <span class="keyword">import</span> android.app.Activity;

- <span class="keyword">import</span> android.os.Bundle;

- <span class="keyword">import</span> android.widget.GridView;

- <span class="keyword">import</span> android.widget.Toast;

- 
- <span class="keyword">public</span> <span class="keyword">class</span> ShowImageActivity <span class="keyword">extends</span> Activity {

- <span class="keyword">private</span> GridView mGridView;

- <span class="keyword">private</span> List<String> list;

- <span class="keyword">private</span> ChildAdapter adapter;

- 
- <span class="annotation">@Override</span>

- <span class="keyword">protected</span> <span class="keyword">void</span> onCreate(Bundle savedInstanceState) {

- <span class="keyword">super</span>.onCreate(savedInstanceState);

- setContentView(R.layout.show_image_activity);

- 
- mGridView = (GridView) findViewById(R.id.child_grid);

- list = getIntent().getStringArrayListExtra(<span class="string">&#8220;data&#8221;</span>);

- 
- adapter = <span class="keyword">new</span> ChildAdapter(<span class="keyword">this</span>, list, mGridView);

- mGridView.setAdapter(adapter);

- 
- }

- 
- <span class="annotation">@Override</span>

- <span class="keyword">public</span> <span class="keyword">void</span> onBackPressed() {

- Toast.makeText(<span class="keyword">this</span>, <span class="string">&#8220;选中 &#8220;</span> + adapter.getSelectItems().size() + <span class="string">&#8221; item&#8221;</span>, Toast.LENGTH_LONG).show();

- <span class="keyword">super</span>.onBackPressed();

- }

- 
- 
- }

GridView的item上面一个我们自定义的MyImageView用来显示图片，另外还有一个CheckBox来记录我们选中情况，Adapter的代码如下

  <div>
    <embed id="ZeroClipboardMovie_9" src="http://static.blog.csdn.net/scripts/ZeroClipboard/ZeroClipboard.swf" type="application/x-shockwave-flash" width="18" height="18" align="middle" name="ZeroClipboardMovie_9">
    </embed>
  </div>
</div>

- <span class="keyword">package</span> com.example.imagescan;

- 
- <span class="keyword">import</span> java.util.ArrayList;

- <span class="keyword">import</span> java.util.HashMap;

- <span class="keyword">import</span> java.util.Iterator;

- <span class="keyword">import</span> java.util.List;

- <span class="keyword">import</span> java.util.Map;

- 
- <span class="keyword">import</span> android.content.Context;

- <span class="keyword">import</span> android.graphics.Bitmap;

- <span class="keyword">import</span> android.graphics.Point;

- <span class="keyword">import</span> android.view.LayoutInflater;

- <span class="keyword">import</span> android.view.View;

- <span class="keyword">import</span> android.view.ViewGroup;

- <span class="keyword">import</span> android.widget.BaseAdapter;

- <span class="keyword">import</span> android.widget.CheckBox;

- <span class="keyword">import</span> android.widget.CompoundButton;

- <span class="keyword">import</span> android.widget.ImageView;

- <span class="keyword">import</span> android.widget.CompoundButton.OnCheckedChangeListener;

- <span class="keyword">import</span> android.widget.GridView;

- 
- <span class="keyword">import</span> com.example.imagescan.MyImageView.OnMeasureListener;

- <span class="keyword">import</span> com.example.imagescan.NativeImageLoader.NativeImageCallBack;

- <span class="keyword">import</span> com.nineoldandroids.animation.AnimatorSet;

- <span class="keyword">import</span> com.nineoldandroids.animation.ObjectAnimator;

- 
- <span class="keyword">public</span> <span class="keyword">class</span> ChildAdapter <span class="keyword">extends</span> BaseAdapter {

- <span class="keyword">private</span> Point mPoint = <span class="keyword">new</span> Point(<span class="number"></span>, <span class="number"></span>);<span class="comment">//用来封装ImageView的宽和高的对象</span>

- <span class="comment">/**</span>

- <span class="comment">     * 用来存储图片的选中情况</span>

- <span class="comment">     */</span>

- <span class="keyword">private</span> HashMap<Integer, Boolean> mSelectMap = <span class="keyword">new</span> HashMap<Integer, Boolean>();

- <span class="keyword">private</span> GridView mGridView;

- <span class="keyword">private</span> List<String> list;

- <span class="keyword">protected</span> LayoutInflater mInflater;

- 
- <span class="keyword">public</span> ChildAdapter(Context context, List<String> list, GridView mGridView) {

- <span class="keyword">this</span>.list = list;

- <span class="keyword">this</span>.mGridView = mGridView;

- mInflater = LayoutInflater.from(context);

- }

- 
- <span class="annotation">@Override</span>

- <span class="keyword">public</span> <span class="keyword">int</span> getCount() {

- <span class="keyword">return</span> list.size();

- }

- 
- <span class="annotation">@Override</span>

- <span class="keyword">public</span> Object getItem(<span class="keyword">int</span> position) {

- <span class="keyword">return</span> list.get(position);

- }

- 
- 
- <span class="annotation">@Override</span>

- <span class="keyword">public</span> <span class="keyword">long</span> getItemId(<span class="keyword">int</span> position) {

- <span class="keyword">return</span> position;

- }

- 
- <span class="annotation">@Override</span>

- <span class="keyword">public</span> View getView(<span class="keyword">final</span> <span class="keyword">int</span> position, View convertView, ViewGroup parent) {

- <span class="keyword">final</span> ViewHolder viewHolder;

- String path = list.get(position);

- 
- <span class="keyword">if</span>(convertView == <span class="keyword">null</span>){

- convertView = mInflater.inflate(R.layout.grid_child_item, <span class="keyword">null</span>);

- viewHolder = <span class="keyword">new</span> ViewHolder();

- viewHolder.mImageView = (MyImageView) convertView.findViewById(R.id.child_image);

- viewHolder.mCheckBox = (CheckBox) convertView.findViewById(R.id.child_checkbox);

- 
- <span class="comment">//用来监听ImageView的宽和高</span>

- viewHolder.mImageView.setOnMeasureListener(<span class="keyword">new</span> OnMeasureListener() {

- 
- <span class="annotation">@Override</span>

- <span class="keyword">public</span> <span class="keyword">void</span> onMeasureSize(<span class="keyword">int</span> width, <span class="keyword">int</span> height) {

- mPoint.set(width, height);

- }

- });

- 
- convertView.setTag(viewHolder);

- }<span class="keyword">else</span>{

- viewHolder = (ViewHolder) convertView.getTag();

- viewHolder.mImageView.setImageResource(R.drawable.friends_sends_pictures_no);

- }

- viewHolder.mImageView.setTag(path);

- viewHolder.mCheckBox.setOnCheckedChangeListener(<span class="keyword">new</span> OnCheckedChangeListener() {

- 
- <span class="annotation">@Override</span>

- <span class="keyword">public</span> <span class="keyword">void</span> onCheckedChanged(CompoundButton buttonView, <span class="keyword">boolean</span> isChecked) {

- <span class="comment">//如果是未选中的CheckBox,则添加动画</span>

- <span class="keyword">if</span>(!mSelectMap.containsKey(position) || !mSelectMap.get(position)){

- addAnimation(viewHolder.mCheckBox);

- }

- mSelectMap.put(position, isChecked);

- }

- });

- 
- viewHolder.mCheckBox.setChecked(mSelectMap.containsKey(position) ? mSelectMap.get(position) : <span class="keyword">false</span>);

- 
- <span class="comment">//利用NativeImageLoader类加载本地图片</span>

- Bitmap bitmap = NativeImageLoader.getInstance().loadNativeImage(path, mPoint, <span class="keyword">new</span> NativeImageCallBack() {

- 
- <span class="annotation">@Override</span>

- <span class="keyword">public</span> <span class="keyword">void</span> onImageLoader(Bitmap bitmap, String path) {

- ImageView mImageView = (ImageView) mGridView.findViewWithTag(path);

- <span class="keyword">if</span>(bitmap != <span class="keyword">null</span> && mImageView != <span class="keyword">null</span>){

- mImageView.setImageBitmap(bitmap);

- }

- }

- });

- 
- <span class="keyword">if</span>(bitmap != <span class="keyword">null</span>){

- viewHolder.mImageView.setImageBitmap(bitmap);

- }<span class="keyword">else</span>{

- viewHolder.mImageView.setImageResource(R.drawable.friends_sends_pictures_no);

- }

- 
- <span class="keyword">return</span> convertView;

- }

- 
- <span class="comment">/**</span>

- <span class="comment">     * 给CheckBox加点击动画，利用开源库nineoldandroids设置动画 </span>

- <span class="comment">     * @param view</span>

- <span class="comment">     */</span>

- <span class="keyword">private</span> <span class="keyword">void</span> addAnimation(View view){

- <span class="keyword">float</span> [] vaules = <span class="keyword">new</span> <span class="keyword">float</span>[]{<span class="number"></span>.5f, <span class="number"></span>.6f, <span class="number"></span>.7f, <span class="number"></span>.8f, <span class="number"></span>.9f, <span class="number">1</span>.0f, <span class="number">1</span>.1f, <span class="number">1</span>.2f, <span class="number">1</span>.3f, <span class="number">1</span>.25f, <span class="number">1</span>.2f, <span class="number">1</span>.15f, <span class="number">1</span>.1f, <span class="number">1</span>.0f};

- AnimatorSet set = <span class="keyword">new</span> AnimatorSet();

- set.playTogether(ObjectAnimator.ofFloat(view, <span class="string">&#8220;scaleX&#8221;</span>, vaules),

- ObjectAnimator.ofFloat(view, <span class="string">&#8220;scaleY&#8221;</span>, vaules));

- set.setDuration(<span class="number">150</span>);

- set.start();

- }

- 
- 
- <span class="comment">/**</span>

- <span class="comment">     * 获取选中的Item的position</span>

- <span class="comment">     * @return</span>

- <span class="comment">     */</span>

- <span class="keyword">public</span> List<Integer> getSelectItems(){

- List<Integer> list = <span class="keyword">new</span> ArrayList<Integer>();

- <span class="keyword">for</span>(Iterator<Map.Entry<Integer, Boolean>> it = mSelectMap.entrySet().iterator(); it.hasNext();){

- Map.Entry<Integer, Boolean> entry = it.next();

- <span class="keyword">if</span>(entry.getValue()){

- list.add(entry.getKey());

- }

- }

- 
- <span class="keyword">return</span> list;

- }

- 
- 
- <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">class</span> ViewHolder{

- <span class="keyword">public</span> MyImageView mImageView;

- <span class="keyword">public</span> CheckBox mCheckBox;

- }

- 
- 
- }

第二个界面的Adapter跟第一个界面差不多，无非多了一个CheckBox用来记录图片选择情况，我们只需要对CheckBox设置setOnCheckedChangeListener监听，微信的选中之后CheckBox有一个动画效果，所以我利用nineoldandroids动画库也给CheckBox加了一个动画效果，直接调用addAnimation()方法就能添加了，getSelectItems()方法就能获取我们选中的item的position了，知道了选中的position，其他的信息就都知道了，微信有对图片进行预览的功能，我这里就不添加了，如果有这个需求可以自行添加，给大家推荐一个https://github.com/chrisbanes/PhotoView

运行项目，效果如下

看起来还不错吧，采用的是异步读取图片，对图片进行了缓存和裁剪，使得在显示本地图片方面比较流畅，GridView滑动也挺流畅的，也有效的避免OOM的产生，工程中有些东西还没有贴完全，有兴趣的朋友可以下载Demo来运行一下，好了，今天的讲解到这里结束了，感谢大家观看，有疑问的朋友可以在下面留言，我会为大家解答的！

项目源码，点击下载

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