Compatibility issues with Android7.0 PopupWindow

Android7.0 Some changes have been made to PopupWindow this commonly used control in this article, which fixes some problems left over before and seems to have introduced some problems. This article takes you through the actual measurement on the 7.0 device and combined with source code analysis to show you about PopupWindow the relevant changes.

Android7.0 The following two problems have been solved. It is emphasized here that it is not to say that Android7.0 these two problems were solved from the beginning, because the details of the specific version have not been delved into. It may be that some other issues have been resolved in other versions as well.

PopupWindow The solution to the disappearance of the click outside and the disappearance of the return button, blog post address:
http://www.cnblogs.com/popfisher/p/5608717.html
Several pain points that have to be complained Android PopupWindow (the pit encountered in implementing the context menu with arrows), blog post address:
http://www.cnblogs.com/popfisher/p/5944054.html

A new problem was introduced in Android 7.0 (this is very embarrassing)

call the update method, PopupWindow the Gravity will change

From the source code to see how 7.0 solves the remaining problems

To solve PopupWindow the problem of not responding to the click outside and disappearing and the return key disappearing, we set a background by ourselves. Android7.0 It is also possible not to set the background in the middle, then its code must have done it. Find the file from api24 the source code of PopupWindow.java , and the method I found inside is preparePopup as follows:

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.");
    }

    // The old decor view may be transitioning out. Make sure it finishes
    // and cleans up before we try to create another one.
    if (mDecorView != null) {
        mDecorView.cancelTransitions();
    }

    // When a background is available, we embed the content view within
    // another view that owns the background drawable.
    if (mBackground != null) {
        mBackgroundView = createBackgroundView(mContentView);
        mBackgroundView.setBackground(mBackground);
    } else {
        mBackgroundView = mContentView;
    }

    mDecorView = createDecorView(mBackgroundView);

    // The background owner should be elevated so that it casts a shadow.
    mBackgroundView.setElevation(mElevation);

    // We may wrap that in another view, so we'll need to manually specify
    // the surface insets.
    p.setSurfaceInsets(mBackgroundView, true /*manual*/, true /*preservePrevious*/);

    mPopupViewInitialLayoutDirectionInherited =
            (mContentView.getRawLayoutDirection() == View.LAYOUT_DIRECTION_INHERIT);
}

重点只需要看 mDecorView = createDecorView(mBackgroundView); 可以看到不管 mBackground 变量是否为空，最终都执行了这句代码，这句代码会多加一层 ViewGroup 把 mBackgroundView 包进去了，里面应该包含了对返回键的处理逻辑，我们再看看 createDecorView 方法源码：

private PopupDecorView createDecorView(View contentView) {
    final ViewGroup.LayoutParams layoutParams = mContentView.getLayoutParams();
    final int height;
    if (layoutParams != null && layoutParams.height == WRAP_CONTENT) {
        height = WRAP_CONTENT;
    } else {
        height = MATCH_PARENT;
    }

    final PopupDecorView decorView = new PopupDecorView(mContext);
    decorView.addView(contentView, MATCH_PARENT, height);
    decorView.setClipChildren(false);
    decorView.setClipToPadding(false);

    return decorView;
}

createDecorView 里面还是没有直接看出对事件的处理，但是里面有个 PopupDecorView 类，应该在里面了吧，继续看：

    private class PopupDecorView extends FrameLayout {
    //......有代码被省略

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

    //......有代码被省略

    @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);
        }
    }

    //......有代码被省略
}

从上面的代码中我们看到了KeyEvent.KEYCODE_BACK 和 MotionEvent.ACTION_OUTSIDE，没错这里有对返回键和其他事件的处理。

至于怎么解决 showAsDropDown 方法弹出位置不对的问题，也就是上文中描述的第二个问题，本文就不贴源码了，感兴趣的可以下载源码去看看，本文只是提供一种解决问题的思路，希望大家能从源码中找到解决问题的办法，这才是作者希望达到的效果。文章末尾会给出 Android7.0 PopupWindow.java 的 java 文件。