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I have a custom view that draws a scrollable bitmap to the screen. In order to initialize it, i need to pass in the size in pixels of the parent layout object. But during the onCreate and onResume functions, the Layout has not been drawn yet, and so layout.getMeasuredHeight() returns 0.

As a workaround, i have added a handler to wait one second and then measure. This works, but its sloppy, and I have no idea how much i can trim the time before I end up before the laout gets drawn.

What I want to know is, how can I detect when a layout gets drawn? Is there an event or callback?

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asked
Oct 11 '11 at 23:47

5,677
7
23

3 Answers

21
accepted

You can add a tree observer to the layout. This should return the correct width and height. onCreate is called before the layout of the child views are done. So the width and height is not calculated yet. To get the height and width. Put this on the onCreate method

LinearLayout layout = (LinearLayout)findViewById(R.id.YOUD VIEW ID);ViewTreeObserver vto = layout.getViewTreeObserver(); vto.addOnGlobalLayoutListener(new OnGlobalLayoutListener() {
@Override public void onGlobalLayout() {
this.layout.getViewTreeObserver().removeGlobalOnLayoutListener(this); int width = layout.getMeasuredWidth(); int height = layout.getMeasuredHeight(); } });

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edited

5,677
7
23

answered
Oct 12 '11 at 4:01

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This worked. Thanks! ViewTreeObserver is exactly the thing I wanted. –

Thanks a lot! Exactly the example I was looking for, including the immediate removal of the listener upon first trigger. –

Question

I have a custom view that draws a scrollable bitmap to the screen. In order to initialize it, i need to pass in the size in pixels of the parent layout object. But during the onCreate and onResume functions, the Layout has not been drawn yet, and so layout.getMeasuredHeight() returns 0.

As a workaround, i have added a handler to wait one second and then measure. This works, but its sloppy, and I have no idea how much i can trim the time before I end up before the laout gets drawn.

What I want to know is, how can I detect when a layout gets drawn? Is there an event or callback?

5,677 7 23 · Accepted Answer · 2011-10-12 04:01:31Z

You can add a tree observer to the layout. This should return the correct width and height. onCreate is called before the layout of the child views are done. So the width and height is not calculated yet. To get the height and width. Put this on the onCreate method

LinearLayout layout = (LinearLayout)findViewById(R.id.YOUD VIEW ID);ViewTreeObserver vto = layout.getViewTreeObserver(); vto.addOnGlobalLayoutListener(new OnGlobalLayoutListener() {
                  @Override     public void onGlobalLayout() {
                      this.layout.getViewTreeObserver().removeGlobalOnLayoutListener(this);         int width  = layout.getMeasuredWidth();        int height = layout.getMeasuredHeight();     } });

This worked. Thanks! ViewTreeObserver is exactly the thing I wanted.
Thanks a lot! Exactly the example I was looking for, including the immediate removal of the listener upon first trigger.