Android - Understanding View.getLocalVisibleRect(Rect)

Question

I'm looking for any clue to understand this method.

There is no info in official Android's SDK documentation about it.

What kind of Rectangle does it return?

Does it filled with Raw coorinates like in MotionEvent?

What if this view isn't visible? Does it returns null? Or some rectangle with some kind of VIEW_INVISIBLE values inside?

Can anyone who has experience of working with this method give me a hand?

Answer 1

From the JavaDoc of getGlobalVisibleRect:

/**
 * If some part of this view is not clipped by any of its parents, then
 * return that area in r in global (root) coordinates. To convert r to local
 * coordinates (without taking possible View rotations into account), offset
 * it by -globalOffset (e.g. r.offset(-globalOffset.x, -globalOffset.y)).
 * If the view is completely clipped or translated out, return false.
 *
 * @param r If true is returned, r holds the global coordinates of the
 * visible portion of this view.
 * @param globalOffset If true is returned, globalOffset holds the dx,dy
 * between this view and its root. globalOffet may be null.
 * @return true if r is non-empty (i.e. part of the view is visible at the
 * root level.
 */

getLocalVisibleRect calls getGlobalVisibleRect and then makes it local as suggested:

r.offset(-offset.x, -offset.y); // make r local`

So:

• It doesn't return a Rectangle, it returns a boolean. But it can set the parameters of a rectangle you pass, and that must be an android.graphics.Rect rectangle;
• The rectangle r will be filled with local coordinates;
• I'm not sure but I think it's the same for visibile and invisible views, while it should return false for views with visibility="gone"