学步园

如上图，上下两栏是一个PopupWindow，然后按键之后再弹出一个PopupWindow：

这个新弹出的PopupWindwo只是一个ListView。

但是我发现这个listView无法接收到OnItemClickListener中的响应，查一下PopupWindow的API，有isFocusable()这个函数。测试一下，果然PopupWindow没有获得焦点。

于是在setOnItemClickListener之前先调用listPopupWindow.setFocusable(true);这是按列表项有反应了，但是按屏幕的其他控件都没法接收到touch事件。

搜索了一下，都说只要设置背景就好了。然后我就找了个图片，果然按其他地方弹出来的listview能自动消失。但是为什么呢？

从别的博客找到了对源码的分析得知了答案：http://www.cnblogs.com/mengdd/p/3569127.html

我把关键的部分复制在下面：

1.显示方法

　　显示提供了两种形式：

　　showAtLocation()显示在指定位置，有两个方法重载：

public void showAtLocation(View parent, int gravity, int x, int y)

public void showAtLocation(IBinder token, int gravity, int x, int y)

showAsDropDown()显示在一个参照物View的周围，有三个方法重载：

public void showAsDropDown(View anchor)

public void showAsDropDown(View anchor, int xoff, int yoff)

public void showAsDropDown(View anchor, int xoff, int yoff, int gravity)

弹出的方法中首先需要preparePopup()，最后再invokePopup()。

　　prepare的方法中可以看到有无背景的分别：

/**
     * <p>Prepare the popup by embedding in into a new ViewGroup if the
     * background drawable is not null. If embedding is required, the layout
     * parameters' height is mnodified to take into account the background's
     * padding.</p>
     *
     * @param p the layout parameters of the popup's content view
     */
    private void preparePopup(WindowManager.LayoutParams p) {
        if (mContentView == null || mContext == null || mWindowManager == null) {
            throw new IllegalStateException("You must specify a valid content view by "
                    + "calling setContentView() before attempting to show the popup.");
        }

        if (mBackground != null) {
            final ViewGroup.LayoutParams layoutParams = mContentView.getLayoutParams();
            int height = ViewGroup.LayoutParams.MATCH_PARENT;
            if (layoutParams != null &&
                    layoutParams.height == ViewGroup.LayoutParams.WRAP_CONTENT) {
                height = ViewGroup.LayoutParams.WRAP_CONTENT;
            }

            // when a background is available, we embed the content view
            // within another view that owns the background drawable
            PopupViewContainer popupViewContainer = new PopupViewContainer(mContext);
            PopupViewContainer.LayoutParams listParams = new PopupViewContainer.LayoutParams(
                    ViewGroup.LayoutParams.MATCH_PARENT, height
            );
            popupViewContainer.setBackgroundDrawable(mBackground);
            popupViewContainer.addView(mContentView, listParams);

            mPopupView = popupViewContainer;
        } else {
            mPopupView = mContentView;
        }
        mPopupViewInitialLayoutDirectionInherited =
                (mPopupView.getRawLayoutDirection() == View.LAYOUT_DIRECTION_INHERIT);
        mPopupWidth = p.width;
        mPopupHeight = p.height;
    }

2.背景是否为空对Touch事件的影响

　　如果有背景，则会在contentView外面包一层PopupViewContainer之后作为mPopupView，如果没有背景，则直接用contentView作为mPopupView。

　　而这个PopupViewContainer是一个内部私有类，它继承了FrameLayout，在其中重写了Key和Touch事件的分发处理：

@Override
        public boolean dispatchKeyEvent(KeyEvent event) {
            if (event.getKeyCode() == KeyEvent.KEYCODE_BACK) {
                if (getKeyDispatcherState() == null) {
                    return super.dispatchKeyEvent(event);
                }

                if (event.getAction() == KeyEvent.ACTION_DOWN
                        && event.getRepeatCount() == 0) {
                    KeyEvent.DispatcherState state = getKeyDispatcherState();
                    if (state != null) {
                        state.startTracking(event, this);
                    }
                    return true;
                } else if (event.getAction() == KeyEvent.ACTION_UP) {
                    KeyEvent.DispatcherState state = getKeyDispatcherState();
                    if (state != null && state.isTracking(event) && !event.isCanceled()) {
                        dismiss();
                        return true;
                    }
                }
                return super.dispatchKeyEvent(event);
            } else {
                return super.dispatchKeyEvent(event);
            }
        }

        @Override
        public boolean dispatchTouchEvent(MotionEvent ev) {
            if (mTouchInterceptor != null && mTouchInterceptor.onTouch(this, ev)) {
                return true;
            }
            return super.dispatchTouchEvent(ev);
        }

        @Override
        public boolean onTouchEvent(MotionEvent event) {
            final int x = (int) event.getX();
            final int y = (int) event.getY();
            
            if ((event.getAction() == MotionEvent.ACTION_DOWN)
                    && ((x < 0) || (x >= getWidth()) || (y < 0) || (y >= getHeight()))) {
                dismiss();
                return true;
            } else if (event.getAction() == MotionEvent.ACTION_OUTSIDE) {
                dismiss();
                return true;
            } else {
                return super.onTouchEvent(event);
            }
        }

由于PopupView本身并没有重写Key和Touch事件的处理，所以如果没有包这个外层容器类，点击Back键或者外部区域是不会导致弹框消失的。