Open PopupWindow and drawing from RightTop to LeftBottom, instead of LeftTop to RightBottom

Question

I know I can use:

myPopup.showAtLocation(layout, Gravity.NO_GRAVITY, x, y);
// OR
myPopup.showAtLocation(layout, Gravity.TOP|Gravity.LEFT, x, y);

To open a PopupWindow that's drawn from [x, y] as the Top-Left of the PopupWindow, drawn towards to Bottom-Right.

What I want instead however, is to draw from [x, y] as the Top-Right of the PopupWindow, drawn towards the Bottom-Left.

Here is a picture to make it more clear (The dot is my [x, y] position and the rectangle is my PopupWindow. The first picture shows how it's normally done, and the second is what I want to achieve.):

So how do I correctly calculate the x and y of the second picture's gray point's location, while knowing the black point's location? I know the y can stay the same, but the x should be changed to something like:

• x minus PopupWindow-width

The problem is that the PopupWindow's width and height are both set to wrap_content, so I don't know the size until after I draw it.

Does this mean I have to draw it (but make it invisible at first), then calculate the new x with the PopupWindow's MeasuredWidth in it's ViewTreeObserver's OnGlobalLayoutListener (to know when it's done rendering and the MeasuredWidth is known), then apply this new x and then make it Visible? Or is there an easier way to just let it draw at the correct position?

PS: I've also changed Gravity.NO_GRAVITY to Gravity.TOP|Gravity.RIGHT, if the PopupWindow is out of the screen it will automatically place it at the border of the Right/Top side (whichever side it's out of the screen).

Answer 1

You could get the size of your popup window by overriding the onMeasure method of the popup window (note that you have to subclass a View in order to do this). After that, you can calculate the offset of the x and y coordinates. Hope this helps.