[AndroidLayout] getWidth() and getHeight()

Error
當 view 還未完整被 layout 前，呼叫 getWidth() and getHeight() 所得的值會是 0。


Solution

• The view's size is assigned when view.onSizeChanged is called with oldw = oldh = 0.
• Assuming your view is visible, its size has been assigned by the time the activity's window receives focus. That is, when activity.onWindowFocusChanged is called with hasFocus = true.

The sequence is roughly:

1. view.onFinishInflate
2. view.onMeasure
3. view.onSizeChanged(width, height, 0, 0)
4. view.onLayout
5. activity.onWindowFocusChanged(true)

// 這樣能確保得到正確的 width and height.
view.post(new Runnable() {
  // TODO
});

* Reference
- Re: When are View.getWidth and getHeight values valid? - joebowbeer - com.googlegroups.android-developers - MarkMail