Android實現滑動刪除操作（PopupWindow）_Android

參考Android仿騰訊QQ實現滑動刪除這篇文章進行學習，文章實現的功能是:在ListView的Item上從右向左滑時，出現刪除按鈕，點擊刪除按鈕把Item刪除，效果

看過文章後，感覺沒有必要把dispatchTouchEvent()和onTouchEvent()兩個方法都重寫，只要重寫onTouchEvent就好了。於是對代碼作了一些調整： 

public class MyListView extends ListView { private static final String TAG = "MyListView"; private int mTouchSlop; private int mXDown; private int mYDown; private int mCurrentPosition; private View mCurrentView; private PopupWindow mPopupWindow; private LayoutInflater mInflater; private boolean isSliding = false; // 為刪除按鈕提供一個回調介面 private DelButtonClickListener mListener; private Button mDelBtn; private int mPopupWindowHeight; private int mPopupWindowWidth; public MyListView(Context context, AttributeSet attrs) {  super(context, attrs);  mInflater = LayoutInflater.from(context);  mTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop();  View view = mInflater.inflate(R.layout.delete_btn, null);  mDelBtn = (Button) view.findViewById(R.id.id_item_btn);  mPopupWindow = new PopupWindow(view, LinearLayout.LayoutParams.WRAP_CONTENT,    LinearLayout.LayoutParams.WRAP_CONTENT);  // 如果需要通過點擊PopupWindow之外的地方使其消失，則需要setFocusable(true).  mPopupWindow.setFocusable(true);  // Android 6.0以前的版本需要setBackgroundDrawable()，  // 才能實現通過點擊PopupWindow之外的地方使其消失的功能。  mPopupWindow.setBackgroundDrawable(new ColorDrawable(0));  // 先調用下measure，否則拿不到寬和高  mPopupWindow.getContentView().measure(0, 0);  mPopupWindowHeight = mPopupWindow.getContentView().getMeasuredHeight();  mPopupWindowWidth = mPopupWindow.getContentView().getMeasuredWidth(); } @Override public boolean onTouchEvent(MotionEvent ev) {  int action = ev.getAction();  int x = (int) ev.getX();  int y = (int) ev.getY();  switch (action){   case MotionEvent.ACTION_DOWN:    isSliding = false;    mXDown = x;    mYDown = y;    mCurrentPosition = pointToPosition(mXDown, mYDown);    View view = getChildAt(mCurrentPosition - getFirstVisiblePosition());    mCurrentView = view;    break;   case MotionEvent.ACTION_MOVE:    int dx = x - mXDown;    int dy = y - mYDown;    Log.d(TAG, "mTouchSlop = " + mTouchSlop + ", dx = " + dx + ", dy = " + dy);    if(mXDown > x && Math.abs(dx) > mTouchSlop && Math.abs(dy) < mTouchSlop){     Log.d(TAG, "isSliding");     isSliding = true;     int[] location = new int[2];     mCurrentView.getLocationOnScreen(location);     mPopupWindow.setAnimationStyle(R.style.popwindow_delete_btn_anim_style);     mPopupWindow.update();     Log.d(TAG, "Height: " + mCurrentView.getHeight() + "," + mPopupWindow.getHeight());     mPopupWindow.showAtLocation(mCurrentView, Gravity.NO_GRAVITY,       location[0] + mCurrentView.getWidth(),       location[1] + mCurrentView.getHeight() / 2 - mPopupWindowHeight / 2);     mDelBtn.setOnClickListener(new OnClickListener() {      @Override      public void onClick(View v) {       mListener.clickHappend(mCurrentPosition);       mPopupWindow.dismiss();      }     });    }   case MotionEvent.ACTION_UP:    // isSliding 如果這裡恢複為false,則後面會執行super.onTouchEvent事件，    // 而AbsListView的onTouchEvent調用了onTouchUp方法，在onTouchUp方法中有可能執行    // performClick.run() --> performItemClick() --> super.performItemClick    // --> mOnItemClickListener.onItemClick，這樣最終觸發Item的點擊。    // 因此此處依舊保持isSliding為true的狀態，而在ACTION_DOWN事件中恢複isSliding為false，    // 畢竟每個事件都以ACTION_DOWN開始。    //isSliding = false;  }  if(isSliding){   return true;  }  return super.onTouchEvent(ev); } public void setDelButtonClickListener(DelButtonClickListener listener){  mListener = listener; } interface DelButtonClickListener{  public void clickHappend(int position); }} 

通過這個例子學習到：
 1、ListView的Item點擊事件的觸發過程：
 自訂ListView的onTouchEvent()  ---調用super.onTouchEvent()---> AbsListView.onTouchEvent() ---MotionEvent.ACTION_UP---> AbsListView.onTouchUp() 
---(有可能)調用performClick.run()---> AbsListView.PerformClick.run() ---調用performItemClick()---> AbsListView.performItemClick()

---(有可能)調用super.performItemClick()---> AdapterView.performItemClick() ---mOnItemClickListener.onItemClick---> OnItemClickListener.onItemClick() 
也就是Item的點擊事件是在MotionEvent.ACTION_UP事件完成的，這樣在自訂ListView的onTouchEvent()中，對MotionEvent.ACTION_UP直接return true消費掉事件，而不要調用super.onTouchEvent。這樣就避免了刪除按鈕與Item點擊事件的衝突。 

2、PopupWindow--通過點擊PopupWindow之外的地方使其消失 
a、需要調用setFocusable()方法（PopupWindow中showAtLocation() --> createPopupLayoutParams() --> computeFlags() --> 設定FLAG_NOT_FOCUSABLE）； 
b、Android 6.0以前的版本需要setBackgroundDrawable()（具體原因見：PopupWindow的使用）。

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