RelativeLayout does exactly what the documentation says it should be
doing. The size and position is are assigned in onLayout(). Here is
the code:
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
// The layout has actually already been performed and the positions
// cached. Apply the cached values to the children.
int count = getChildCount();
for (int i = 0; i < count; i++) {
View child = getChildAt(i);
if (child.getVisibility() != GONE) {
RelativeLayout.LayoutParams st =
(RelativeLayout.LayoutParams) child.getLayoutParams();
child.layout(st.mLeft, st.mTop, st.mRight, st.mBottom);
}
}
}
It's just using cached values computed in onMeasure(), which does not
go against the concepts of ViewGroups as defined by the javadoc.
On Fri, Jun 12, 2009 at 10:00 AM, Matt<[email protected]> wrote:
>
> According to
> http://developer.android.com/guide/topics/ui/custom-components.html:
>
> onMeasure(int, int) Called to determine the size requirements for this
> view and all of its children.
> onLayout(boolean, int, int, int, int) Called when this view should
> assign a size and position to all of its children.
>
> RelativeLayout doesn't do this; it actually assigns a size and
> position to all of its children in onMeasure. From the source code of
> RelativeLayout:
> �...@override
> protected void onLayout(boolean changed, int l, int t, int r, int
> b) {
> // The layout has actually already been performed and the
> positions
> // cached. Apply the cached values to the children.
>
> This is bad because, I wanted to override a RelativeLayout and assign
> it a specific height. However, the children of this RelativeLayout
> would not respect the height I assigned, because the children assign
> themselves positions and sizes in onMeasure. And therefore the
> children don't fit in the RelativeLayout.
>
> IMHO it's a bad sign of the design when the actual framework doesn't
> follow its own design. I know this sounds like a flame or a rant, but
> I'm just trying to point out what I believe to be a underlying problem
> here. If you can't override a RelativeLayout then it should have been
> declared final (but that's too drastic). Perhaps the onMeasure and
> onLayout need to be rethought (guess it's too late for that :). At
> the very least, the documentation should be updated so that one knows
> that when subclassing RelativeLayout, that the size and position of
> all of its children are actually assigned in onMeasure and onLayout.
>
>
> >
>
--
Romain Guy
Android framework engineer
[email protected]
Note: please don't send private questions to me, as I don't have time
to provide private support. All such questions should be posted on
public forums, where I and others can see and answer them
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