Thanks for the reply.
The custom layout isn't doing *just* that - it's doing a lot of other
stuff, and I figured it'd be more practical to just have it layout all it's
children as they should be, instead of using a more traditional layout
(like RelativeLayout or FrameLayout) and just omitting rules and margins.
It's trivial to use traditional layouts to achieve the net result, but
when I ran into the issue, it made me curious why the LayoutParams were
being queried at all, since my overriden onMeasure and onLayout didn't
examine them. I believe that they're still being looked at in the various
measure methods, as called by parent containers.
On Sunday, March 3, 2013 2:35:07 AM UTC-6, Piren wrote:
>
> I'm no expert on the layout machenism of android, but you dont really need
> a reference to the LayoutParams to do these calculations since onMeasure
> gets the "processed" values of these params. the width and height
> MeasureSpecs contain the size and mode as recommended by the layout params.
> What you're doing might be working in the instance you're testing on, but
> might fail on others.
>
> P.S - Maybe its because of there's missing code here, but it seems like
> you're just having the parent layout having the same size as the child
> layout (basically both have wrap_content on width and height)... why do you
> need a custom class for that?
>
> On Saturday, March 2, 2013 8:10:17 AM UTC+2, momo wrote:
>>
>> I have a custom ViewGroup that's only ever managing the size and position
>> of one child. I've override onMeasure and onLayout so that LayoutParams
>> are never examined, yet it fails unless I do provide LayoutParams. Here
>> are abbreviated summaries of the relevant portions of the class:
>>
>>
>> public class SomeSpecialLayoutManager extends ViewGroup {
>>
>> @Override
>> protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
>> {
>> measureChildren(widthMeasureSpec, heightMeasureSpec);
>> int w = mChild.getMeasuredWidth();
>> int h = mChild.getMeasuredHeight();
>> w = Math.max(w, getSuggestedMinimumWidth());
>> h = Math.max(h, getSuggestedMinimumHeight());
>> w = resolveSize(w, widthMeasureSpec);
>> h = resolveSize(h, heightMeasureSpec);
>> setMeasuredDimension(w, h);
>> }
>>
>> @Override
>> protected void onLayout(boolean changed, int l, int t, int r, int b) {
>> mChild.layout( 0, 0, mWidth, mHeight );
>> }
>> }
>>
>>
>> Using the above, the following *does* work:
>>
>> LayoutParams lp = mChild.getLayoutParams();
>> lp.width = mWidth;
>> lp.height = mHeight;
>> mChild.setLayoutParams( lp );
>>
>> But since neither `onMeasure` nor `onLayout` even makes reference to
>> `LayoutParams`, I wonder why it's required, or even how it's referenced at
>> all. I would assume that since the layout pass grabs `mWidth` and
>> `mHeight` directly, there'd be no need for the `LayoutParams` at all - and
>> that a call to requestLayout would update it appropriately.
>>
>> However, when I isolate the above in a small program outside of a
>> complicated View tree with scrolling layers that exceed "normal" container
>> sizes, it *does* work as expected, so I have to assume the issue is in the
>> measure pass.
>>
>> I've read as much documentation as I can find about what's going on
>> during the measure and layout passes, and examined the source, but I
>> believe I must be missing something.
>>
>> TYIA.
>>
>
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