Custom view added to WindowManager, pass events to underlying window depending on state

Question

I have a fairly complicated situation where I need to either process events in a custom view, which is added via WindowManager, or pass them to the underlying window if it is outside of the wanted area. The wanted area is the containerView where it can be smaller from the root view itself, or may have equal width / height.

The view has a size of 28x28, but it can grow up until 60x60. The growing part is done with ValueAnimator where current width and target width is determined by the ValueAnimator.getAnimatedValue() (in this case, between 28 and 60). The window needs to consume the event if it has been clicked on, or the target view which may be smaller than the window itself, is clicked.

An example of the layout looks like this:

<FrameLayout android:layout_width="wrap_content"
    android:layout_height="wrap_content">

    <FrameLayout android:id="@+id/containerView"
         android:layout_width="28dp"
         android:layout_height="28dp"
         android:layout_gravity="center">

         <!-- rest of the view, not important -->

         <!-- the containerView can have 28x28 size or
                   60x60 size -->

    </FrameLayout>

</FrameLayout>

The animated view is the one that is defined with android:id="@+id/containerView".

I've tried to attach the view using regular layout params, like this, to make the window layout dynamic:

WindowManager manager = context.getSystemService(WindowManager.class);
View rootView = LayoutInflater.from(context).inflate(resId, null, false);

WindowManager.LayoutParams params = new WindowManager.LayoutParams();

params.width = WindowManager.LayoutParams.WRAP_CONTENT;
params.height = WindowManager.LayoutParams.WRAP_CONTENT;
params.type = WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY;
params.flags = FLAG_NOT_FOCUSABLE | FLAG_WATCH_OUTSIDE_TOUCH;

manager.addView(rootView, params);

And this similar code block adds the view with 28x28 size, that's not a problem. However, while animating to 60x60 size depending on a state change (on containerView), the animation flickers a lot. I guess it happens because both view itself and the window needs to be re-sized. I've tried to use setLayerType(HARDWARE, null) but that didn't seem to work. Then I've found another workaround, which is increasing the size of the window directly, before starting the animation, by giving it fixed width-height values, like this:

params.width = dpToPx(60);
params.height = dpToPx(60);

manager.updateViewLayout(rootView, params);

And after this, I start the growing animation, which changes the containerView width and height gradually. With this way, animation is smooth, even on lower-end devices so I think it's a good optimization.

The problem begins with the window size change. You see, containerView has to have the attribute android:layout_gravity="center" to position the view to window's center. But, increasing the window width and height changes the view's position. To overcome that, I've decided to write another approach by doing something like this:

// This method is inside the root view, which contains
// the WindowManager.LayoutParams as its layout params.
private void setWindowSize(int widthPx, int heightPx)
{
    WindowManager.LayoutParams params = getLayoutParams(); // ignore cast

    int oldWidth = params.width;
    int oldHeight = params.height;

    int differenceWidth = widthPx - oldWidth;
    int differenceHeight = heightPx - oldHeight;

    // Position the view relatively to the window so 
    // it should look like its position is not changed
    // due to containerView's center layout_gravity.

    params.x -= differenceWidth / 2;
    params.y -= differenceHeight / 2;
    params.width = widthPx;
    params.height = heightPx;

    // Update itself since this is already the root view.
    manager.updateViewLayout(this, params);
}

The code above was causing the position change happening with animation. Hence, I've searched if this animation can be disabled, and found an answer here which seems to be working with Android 10 emulator. However, I don't think this is a reliable approach, as most manufacturers change source codes of framework classes to implement their own themes etc. so I'm looking for a more reliable approach. The change also cause a flicker due to the containerView.onLayout() operation, presumably happening after manager.updateViewLayout() is executed, where it appears on top-left for one frame and on center on the 2nd frame, visible to the eyes.

At this point, I can only think of some ways to prevent these bugs:

1) Process touch events only on certain states (such as the coordinates intercepting the containerView)

2) Make the view non-touchable after receiving MotionEvent.ACTION_OUTSIDE which will indicate a touch event happened outside of the view's boundaries.

1st one has a flaw: If the view is clickable in all cases, it becomes clickable starting from the root view, and once the touch event is received from that view, it is not transferred to other windows (a.k.a underlying applications) which cause an issue.

2nd one seemed a good approach for me, but the event MotionEvent.ACTION_OUTSIDE does not contain any specific x or y coordinates so it is impossible to tell if the event occurred in window's boundaries. If this was possible, I'd add FLAG_NOT_TOUCHABLE to layout params and updated the view, and removed that flag if the touch is to be processed.

So, my question is:

Can a custom view, that has been added with a WindowManager choose to deliver the events further based on, i don't know, returning false from dispatchTouchEvent() or something? Or, is there a way to receive all touch events even outside our application with the specific screen coordinates so I can change the window flags depending on it?

Any help is appreciated, thank you very much.

Answer 1

I was able to resolve the issue by applying an ugly hack. I've used a second window, where the window itself is full screen and contains flags FLAG_NOT_FOCUSABLE and FLAG_NOT_TOUCHABLE and since the touch is disabled the events are passed below window.

The window-resize flickering depending on the animation was the cause, so I've thought about using a temporary view, added the view to a second window, by getting the cache of the view itself using a bitmap and a canvas (the states are cached and recycled by the way), and making the image view visible, setting the view on the original window as INVISIBLE and after making sure it became invisible (by using ViewTreeObserver.addOnDrawListener because the draw function is called) changing window size.

With this approach, the view becomes already invisible while the window size is changed, and translated accordingly, which eliminated the possibility of the buggy view.

Then, after the layout is complete (I've also made sure by using ViewTreeObserver.addOnGlobalLayoutListener() and waiting for the view to be placed on the target coordinates relative to parent), switched the views. Extra memory is used because of the extra added window and image view and bitmap, but the issue seems to be resolved.

The only remaining thing is how to disable window animations with the call windowManager.updateViewLayout() because the flag that the other question mentioned is apparently added in API 18, whereas this app targets to API 16. On the rest of the emulators and the devices that I've tested on seem to have this flag consistently, and the window translate animations seem to be disabled successfully.