private PreviewItemDrawingParams computePreviewItemDrawingParams(
int index, PreviewItemDrawingParams params) {
index = NUM_ITEMS_IN_PREVIEW - index - 1;
float r = (index * 1.0f) / (NUM_ITEMS_IN_PREVIEW - 1);
float scale = (1 - PERSPECTIVE_SCALE_FACTOR * (1 - r));
float offset = (1 - r) * mMaxPerspectiveShift;
float scaledSize = scale * mBaselineIconSize;
float scaleOffsetCorrection = (1 - scale) * mBaselineIconSize;
// We want to imagine our coordinates from the bottom left, growing up and to the
// right. This is natural for the x-axis, but for the y-axis, we have to invert things.
float transY = mAvailableSpaceInPreview - (offset + scaledSize + scaleOffsetCorrection);
float transX = offset + scaleOffsetCorrection;
float totalScale = mBaselineIconScale * scale;
final int overlayAlpha = (int) (80 * (1 - r));
if (params == null) {
params = new PreviewItemDrawingParams(transX, transY, totalScale, overlayAlpha);
} else {
params.transX = transX;
params.transY = transY;
params.scale = totalScale;
params.overlayAlpha = overlayAlpha;
}
return params;
}
private float getLocalCenterForIndex(int index, int[] center) {
mParams = computePreviewItemDrawingParams(Math.min(NUM_ITEMS_IN_PREVIEW, index), mParams);
mParams.transX += mPreviewOffsetX;
mParams.transY += mPreviewOffsetY;
float offsetX = mParams.transX + (mParams.scale * mIntrinsicIconSize) / 2;
float offsetY = mParams.transY + (mParams.scale * mIntrinsicIconSize) / 2;
center[0] = Math.round(offsetX);
center[1] = Math.round(offsetY);
return mParams.scale;
}
@Override
protected void dispatchDraw(Canvas canvas) {
super.dispatchDraw(canvas);
if (mFolder == null) return;
if (mFolder.getItemCount() == 0 && !mAnimating) return;
ArrayList<View> items = mFolder.getItemsInReadingOrder(false);
Drawable d;
TextView v;
// Update our drawing parameters if necessary
if (mAnimating) {
computePreviewDrawingParams(mAnimParams.drawable);
} else {
v = (TextView) items.get(0);
d = v.getCompoundDrawables()[1];
computePreviewDrawingParams(d);
}
int nItemsInPreview = Math.min(items.size(), NUM_ITEMS_IN_PREVIEW);
if (!mAnimating) {
for (int i = nItemsInPreview - 1; i >= 0; i--) {
v = (TextView) items.get(i);
d = v.getCompoundDrawables()[1];
mParams = computePreviewItemDrawingParams(i, mParams);
mParams.drawable = d;
drawPreviewItem(canvas, mParams);
}
} else {
drawPreviewItem(canvas, mAnimParams);
}
}
private void animateFirstItem(final Drawable d, int duration) {
computePreviewDrawingParams(d);
final PreviewItemDrawingParams finalParams = computePreviewItemDrawingParams(0, null);
final float scale0 = 1.0f;
final float transX0 = (mAvailableSpaceInPreview - d.getIntrinsicWidth()) / 2;
final float transY0 = (mAvailableSpaceInPreview - d.getIntrinsicHeight()) / 2;
mAnimParams.drawable = d;
ValueAnimator va = ValueAnimator.ofFloat(0f, 1.0f);
va.addUpdateListener(
new AnimatorUpdateListener() {
public void onAnimationUpdate(ValueAnimator animation) {
float progress = (Float) animation.getAnimatedValue();
mAnimParams.transX = transX0 + progress * (finalParams.transX - transX0);
mAnimParams.transY = transY0 + progress * (finalParams.transY - transY0);
mAnimParams.scale = scale0 + progress * (finalParams.scale - scale0);
invalidate();
}
});
va.addListener(
new AnimatorListenerAdapter() {
@Override
public void onAnimationStart(Animator animation) {
mAnimating = true;
}
@Override
public void onAnimationEnd(Animator animation) {
mAnimating = false;
}
});
va.setDuration(duration);
va.start();
}
