[英]Resizing Views before drawing
在我的布局中,我有一个包含4个自定义ImageView的GridView。 我将GridView的可见性设置为不可见,直到首先调整所有ImageView的大小,但是当显示GridView时,ImageViews仍然短暂闪烁。
每个ImageView都会创建单独的侦听器以缩放其大小:
//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);
}
}
});
我还尝试过在onGlobalLayout方法中调整它们的大小(相同的结果)并覆盖onMeasure方法(此时,父视图仍然为null)。
我怀疑在onPreDraw()中更改视图为时已晚,但是是否可以在内部调用更早的方法来确定所有视图是否已被测量?
尝试在mAnswerGridView.setVisibility(View.VISIBLE);
之前调用mAnswerGridView.requestLayout()
mAnswerGridView.setVisibility(View.VISIBLE);
这可能不起作用,因为正如Android开发人员所述
这将安排视图树的布局遍历。
因此,您最好强制重新布局:
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()); }
我创建了一个处理程序,可以在调用requestLayout之后立即安排设置可见性。
在这种情况下效果很好。
ResizeCounter.addCounterListener(new OnResizeCounterChangeListener() {
@Override
public void onResizeCounterChanged() {
if (ResizeCounter.getCounter() == 4) {
mAnswerGridView.requestLayout();
Handler handler = new Handler();
handler.post(new Runnable() {
@Override
public void run() {
mAnswerGridView.setVisibility(View.VISIBLE);
}
});
}
}
});
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