Android 对ScrollView滚动监听，实现美团、大众点评的购买悬浮效果

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

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

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

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

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

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

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

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

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

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

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

- <span class="keyword">import</span> com.example.meituandemo.MyScrollView.OnScrollListener;

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

- <span class="comment"> * 博客地址: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> MainActivity <span class="keyword">extends</span> Activity <span class="keyword">implements</span> OnScrollListener{

- <span class="keyword">private</span> MyScrollView myScrollView;

- <span class="keyword">private</span> LinearLayout mBuyLayout;

- <span class="keyword">private</span> WindowManager mWindowManager;

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

- <span class="comment">     * 手机屏幕宽度</span>

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

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

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

- <span class="comment">     * 悬浮框View</span>

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

- <span class="keyword">private</span> <span class="keyword">static</span> View suspendView;

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

- <span class="comment">     * 悬浮框的参数</span>

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

- <span class="keyword">private</span> <span class="keyword">static</span> WindowManager.LayoutParams suspendLayoutParams;

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

- <span class="comment">     * 购买布局的高度</span>

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

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

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

- <span class="comment">     * myScrollView与其父类布局的顶部距离</span>

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

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

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

- <span class="comment">     * 购买布局与其父类布局的顶部距离</span>

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

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

- 
- 
- <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);

- 
- myScrollView = (MyScrollView) findViewById(R.id.scrollView);

- mBuyLayout = (LinearLayout) findViewById(R.id.buy);

- 
- myScrollView.setOnScrollListener(<span class="keyword">this</span>);

- mWindowManager = (WindowManager) getSystemService(Context.WINDOW_SERVICE);

- screenWidth = mWindowManager.getDefaultDisplay().getWidth();

- }

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

- <span class="comment">     * 窗口有焦点的时候，即所有的布局绘制完毕的时候，我们来获取购买布局的高度和myScrollView距离父类布局的顶部位置</span>

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

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

- <span class="keyword">public</span> <span class="keyword">void</span> onWindowFocusChanged(<span class="keyword">boolean</span> hasFocus) {

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

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

- buyLayoutHeight = mBuyLayout.getHeight();

- buyLayoutTop = mBuyLayout.getTop();

- 
- myScrollViewTop = myScrollView.getTop();

- }

- }

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

- <span class="comment">     * 滚动的回调方法，当滚动的Y距离大于或者等于 购买布局距离父类布局顶部的位置，就显示购买的悬浮框</span>

- <span class="comment">     * 当滚动的Y的距离小于 购买布局距离父类布局顶部的位置加上购买布局的高度就移除购买的悬浮框</span>

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

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

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

- <span class="keyword">public</span> <span class="keyword">void</span> onScroll(<span class="keyword">int</span> scrollY) {

- <span class="keyword">if</span>(scrollY >= buyLayoutTop){

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

- showSuspend();

- }

- }<span class="keyword">else</span> <span class="keyword">if</span>(scrollY <= buyLayoutTop + buyLayoutHeight){

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

- removeSuspend();

- }

- }

- }

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

- <span class="comment">     * 显示购买的悬浮框</span>

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

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

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

- suspendView = LayoutInflater.from(<span class="keyword">this</span>).inflate(R.layout.buy_layout, <span class="keyword">null</span>);

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

- suspendLayoutParams = <span class="keyword">new</span> LayoutParams();

- suspendLayoutParams.type = LayoutParams.TYPE_PHONE; <span class="comment">//悬浮窗的类型，一般设为2002，表示在所有应用程序之上，但在状态栏之下 </span>

- suspendLayoutParams.format = PixelFormat.RGBA_8888;

- suspendLayoutParams.flags = LayoutParams.FLAG_NOT_TOUCH_MODAL

- | LayoutParams.FLAG_NOT_FOCUSABLE;  <span class="comment">//悬浮窗的行为，比如说不可聚焦，非模态对话框等等 </span>

- suspendLayoutParams.gravity = Gravity.TOP;  <span class="comment">//悬浮窗的对齐方式</span>

- suspendLayoutParams.width = screenWidth;

- suspendLayoutParams.height = buyLayoutHeight;

- suspendLayoutParams.x = <span class="number"></span>;  <span class="comment">//悬浮窗X的位置</span>

- suspendLayoutParams.y = myScrollViewTop;  <span class="comment">////悬浮窗Y的位置</span>

- }

- }

- 
- mWindowManager.addView(suspendView, suspendLayoutParams);

- }

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

- <span class="comment">     * 移除购买的悬浮框</span>

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

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

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

- mWindowManager.removeView(suspendView);

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

- }

- }

- 
- }