tomwyr tomwyr - 7 months ago 32
Java Question

Resizing Views before drawing

In my layout I have a GridView containing 4 custom ImageViews. I'm setting GridView's visibility to invisible until all ImageViews are resized at first but when the GridView is shown, there's a short blink with ImageViews still unchanged.

blink for a split second

views are resized in a moment

Each ImageView creates separate listener in order to scale its size:

//Setting new params as half of parent's size and increasing counter

if (getViewTreeObserver().isAlive()) {
final ViewTreeObserver viewTreeObserver = getViewTreeObserver();
viewTreeObserver.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
@Override
public boolean onPreDraw() {
getViewTreeObserver().removeOnPreDrawListener(this);

View parent = (View) getParent();
int dimension = Math.min(parent.getWidth(), parent.getHeight()) / 2;
mThisImageView.setLayoutParams(new AbsListView.LayoutParams(dimension, dimension));
ResizeCounter.setCounter(ResizeCounter.getCounter() + 1);

return true;
}
});
}




//Activity listens to the moment when all ImageViews have been resized

ResizeCounter.addCounterListener(new OnResizeCounterChangeListener() {
@Override
public void onResizeCounterChanged() {
if (ResizeCounter.getCounter() == 4) {
mAnswerGridView.setVisibility(View.VISIBLE);
}
}
});


I've also tried to resize them in onGlobalLayout method (same result) and to override onMeasure method (parent View is still null at this point).

I suspect that it's too late to change views in onPreDraw() but is there a method that can be called earlier inside which I can be sure that all views have been measured?

Answer

Try to call mAnswerGridView.requestLayout() before mAnswerGridView.setVisibility(View.VISIBLE);

This may not work because as it's stated at Android Developers

This will schedule a layout pass of the view tree.

So you may better force relayout:

relayoutChildren(View view) {
view.measure(
    View.MeasureSpec.makeMeasureSpec(view.getMeasuredWidth(), View.MeasureSpec.EXACTLY),
    View.MeasureSpec.makeMeasureSpec(view.getMeasuredHeight(), View.MeasureSpec.EXACTLY));
view.layout(view.getLeft(), view.getTop(), view.getRight(), view.getBottom()); }
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