@Override
public void onScrollChanged(int scrollY, boolean firstScroll, boolean dragging) {
// Translate overlay and image
float flexibleRange = mFlexibleSpaceImageHeight - mActionBarSize;
int minOverlayTransitionY = mActionBarSize - mOverlayView.getHeight();
ViewHelper.setTranslationY(
mOverlayView, ScrollUtils.getFloat(-scrollY, minOverlayTransitionY, 0));
ViewHelper.setTranslationY(
mImageView, ScrollUtils.getFloat(-scrollY / 2, minOverlayTransitionY, 0));
// Change alpha of overlay
ViewHelper.setAlpha(mOverlayView, ScrollUtils.getFloat((float) scrollY / flexibleRange, 0, 1));
// Scale title text
float scale =
1
+ ScrollUtils.getFloat(
(flexibleRange - scrollY) / flexibleRange, 0, MAX_TEXT_SCALE_DELTA);
ViewHelper.setPivotX(mTitleView, 0);
ViewHelper.setPivotY(mTitleView, 0);
ViewHelper.setScaleX(mTitleView, scale);
ViewHelper.setScaleY(mTitleView, scale);
// Translate title text
int maxTitleTranslationY = (int) (mFlexibleSpaceImageHeight - mTitleView.getHeight() * scale);
int titleTranslationY = maxTitleTranslationY - scrollY;
ViewHelper.setTranslationY(mTitleView, titleTranslationY);
// Translate FAB
int maxFabTranslationY = mFlexibleSpaceImageHeight - mFab.getHeight() / 2;
float fabTranslationY =
ScrollUtils.getFloat(
-scrollY + mFlexibleSpaceImageHeight - mFab.getHeight() / 2,
mActionBarSize - mFab.getHeight() / 2,
maxFabTranslationY);
if (Build.VERSION.SDK_INT < Build.VERSION_CODES.HONEYCOMB) {
// On pre-honeycomb, ViewHelper.setTranslationX/Y does not set margin,
// which causes FAB's OnClickListener not working.
FrameLayout.LayoutParams lp = (FrameLayout.LayoutParams) mFab.getLayoutParams();
lp.leftMargin = mOverlayView.getWidth() - mFabMargin - mFab.getWidth();
lp.topMargin = (int) fabTranslationY;
mFab.requestLayout();
} else {
ViewHelper.setTranslationX(mFab, mOverlayView.getWidth() - mFabMargin - mFab.getWidth());
ViewHelper.setTranslationY(mFab, fabTranslationY);
}
// Show/hide FAB
if (fabTranslationY < mFlexibleSpaceShowFabOffset) {
hideFab();
} else {
showFab();
}
}
private void translateTab(int scrollY, boolean animated) {
int flexibleSpaceImageHeight =
getResources().getDimensionPixelSize(R.dimen.flexible_space_image_height);
int tabHeight = getResources().getDimensionPixelSize(R.dimen.tab_height);
View imageView = findViewById(R.id.image);
View overlayView = findViewById(R.id.overlay);
TextView titleView = (TextView) findViewById(R.id.title);
// Translate overlay and image
float flexibleRange = flexibleSpaceImageHeight - getActionBarSize();
int minOverlayTransitionY = tabHeight - overlayView.getHeight();
ViewHelper.setTranslationY(
overlayView, ScrollUtils.getFloat(-scrollY, minOverlayTransitionY, 0));
ViewHelper.setTranslationY(
imageView, ScrollUtils.getFloat(-scrollY / 2, minOverlayTransitionY, 0));
// Change alpha of overlay
ViewHelper.setAlpha(overlayView, ScrollUtils.getFloat((float) scrollY / flexibleRange, 0, 1));
// Scale title text
float scale =
1
+ ScrollUtils.getFloat(
(flexibleRange - scrollY - tabHeight) / flexibleRange, 0, MAX_TEXT_SCALE_DELTA);
setPivotXToTitle(titleView);
ViewHelper.setPivotY(titleView, 0);
ViewHelper.setScaleX(titleView, scale);
ViewHelper.setScaleY(titleView, scale);
// Translate title text
int maxTitleTranslationY = flexibleSpaceImageHeight - tabHeight - getActionBarSize();
int titleTranslationY = maxTitleTranslationY - scrollY;
ViewHelper.setTranslationY(titleView, titleTranslationY);
// If tabs are moving, cancel it to start a new animation.
ViewPropertyAnimator.animate(mSlidingTabLayout).cancel();
// Tabs will move between the top of the screen to the bottom of the image.
float translationY =
ScrollUtils.getFloat(
-scrollY + mFlexibleSpaceHeight - mTabHeight, 0, mFlexibleSpaceHeight - mTabHeight);
if (animated) {
// Animation will be invoked only when the current tab is changed.
ViewPropertyAnimator.animate(mSlidingTabLayout)
.translationY(translationY)
.setDuration(200)
.start();
} else {
// When Fragments' scroll, translate tabs immediately (without animation).
ViewHelper.setTranslationY(mSlidingTabLayout, translationY);
}
}
public void testGetFloat() {
Assert.assertEquals(1.0f, ScrollUtils.getFloat(1, 0, 2));
assertEquals(0.0f, ScrollUtils.getFloat(-1, 0, 2));
assertEquals(2.0f, ScrollUtils.getFloat(3, 0, 2));
}
