src/com/android/launcher3/folder/FolderAnimationManager.java - platform/packages/apps/Launcher3 - Git at Google

 /*
  * Copyright (C) 2017 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 package com.android.launcher3.folder;

 import static com.android.launcher3.BubbleTextView.TEXT_ALPHA_PROPERTY;
 import static com.android.launcher3.LauncherAnimUtils.SCALE_PROPERTY;
 import static com.android.launcher3.folder.ClippedFolderIconLayoutRule.MAX_NUM_ITEMS_IN_PREVIEW;
 import static com.android.launcher3.graphics.IconShape.getShape;
 import static com.android.launcher3.icons.GraphicsUtils.setColorAlphaBound;

 import android.animation.Animator;
 import android.animation.AnimatorListenerAdapter;
 import android.animation.AnimatorSet;
 import android.animation.ObjectAnimator;
 import android.animation.TimeInterpolator;
 import android.content.Context;
 import android.content.res.Resources;
 import android.graphics.Rect;
 import android.graphics.drawable.GradientDrawable;
 import android.util.Property;
 import android.view.View;
 import android.view.animation.AnimationUtils;

 import androidx.core.graphics.ColorUtils;

 import com.android.launcher3.BubbleTextView;
 import com.android.launcher3.CellLayout;
 import com.android.launcher3.Launcher;
 import com.android.launcher3.R;
 import com.android.launcher3.ResourceUtils;
 import com.android.launcher3.ShortcutAndWidgetContainer;
 import com.android.launcher3.Utilities;
 import com.android.launcher3.anim.PropertyResetListener;
 import com.android.launcher3.dragndrop.DragLayer;
 import com.android.launcher3.util.Themes;

 import java.util.List;

 /**
  * Manages the opening and closing animations for a {@link Folder}.
  *
  * All of the animations are done in the Folder.
  * ie. When the user taps on the FolderIcon, we immediately hide the FolderIcon and show the Folder
  * in its place before starting the animation.
  */
 public class FolderAnimationManager {

     private Folder mFolder;
     private FolderPagedView mContent;
     private GradientDrawable mFolderBackground;

     private FolderIcon mFolderIcon;
     private PreviewBackground mPreviewBackground;

     private Context mContext;
     private Launcher mLauncher;

     private final boolean mIsOpening;

     private final int mDuration;
     private final int mDelay;

     private final TimeInterpolator mFolderInterpolator;
     private final TimeInterpolator mLargeFolderPreviewItemOpenInterpolator;
     private final TimeInterpolator mLargeFolderPreviewItemCloseInterpolator;

     private final PreviewItemDrawingParams mTmpParams = new PreviewItemDrawingParams(0, 0, 0, 0);


     public FolderAnimationManager(Folder folder, boolean isOpening) {
         mFolder = folder;
         mContent = folder.mContent;
         mFolderBackground = (GradientDrawable) mFolder.getBackground();

         mFolderIcon = folder.mFolderIcon;
         mPreviewBackground = mFolderIcon.mBackground;

         mContext = folder.getContext();
         mLauncher = folder.mLauncher;

         mIsOpening = isOpening;

         Resources res = mContent.getResources();
         mDuration = res.getInteger(R.integer.config_materialFolderExpandDuration);
         mDelay = res.getInteger(R.integer.config_folderDelay);

         mFolderInterpolator = AnimationUtils.loadInterpolator(mContext,
                 R.interpolator.folder_interpolator);
         mLargeFolderPreviewItemOpenInterpolator = AnimationUtils.loadInterpolator(mContext,
                 R.interpolator.large_folder_preview_item_open_interpolator);
         mLargeFolderPreviewItemCloseInterpolator = AnimationUtils.loadInterpolator(mContext,
                 R.interpolator.large_folder_preview_item_close_interpolator);
     }


     /**
      * Prepares the Folder for animating between open / closed states.
      */
     public AnimatorSet getAnimator() {
         final DragLayer.LayoutParams lp = (DragLayer.LayoutParams) mFolder.getLayoutParams();
         ClippedFolderIconLayoutRule rule = mFolderIcon.getLayoutRule();
         final List<BubbleTextView> itemsInPreview = mFolderIcon.getPreviewItems();

         // Match position of the FolderIcon
         final Rect folderIconPos = new Rect();
         float scaleRelativeToDragLayer = mLauncher.getDragLayer()
                 .getDescendantRectRelativeToSelf(mFolderIcon, folderIconPos);
         int scaledRadius = mPreviewBackground.getScaledRadius();
         float initialSize = (scaledRadius * 2) * scaleRelativeToDragLayer;

         // Match size/scale of icons in the preview
         float previewScale = rule.scaleForItem(itemsInPreview.size());
         float previewSize = rule.getIconSize() * previewScale;
         float initialScale = previewSize / itemsInPreview.get(0).getIconSize()
                 * scaleRelativeToDragLayer;
         final float finalScale = 1f;
         float scale = mIsOpening ? initialScale : finalScale;
         mFolder.setScaleX(scale);
         mFolder.setScaleY(scale);
         mFolder.setPivotX(0);
         mFolder.setPivotY(0);

         // We want to create a small X offset for the preview items, so that they follow their
         // expected path to their final locations. ie. an icon should not move right, if it's final
         // location is to its left. This value is arbitrarily defined.
         int previewItemOffsetX = (int) (previewSize / 2);
         if (Utilities.isRtl(mContext.getResources())) {
             previewItemOffsetX = (int) (lp.width * initialScale - initialSize - previewItemOffsetX);
         }

         final int paddingOffsetX = (int) ((mFolder.getPaddingLeft() + mContent.getPaddingLeft())
                 * initialScale);
         final int paddingOffsetY = (int) ((mFolder.getPaddingTop() + mContent.getPaddingTop())
                 * initialScale);

         int initialX = folderIconPos.left + mPreviewBackground.getOffsetX() - paddingOffsetX
                 - previewItemOffsetX;
         int initialY = folderIconPos.top + mPreviewBackground.getOffsetY() - paddingOffsetY;
         final float xDistance = initialX - lp.x;
         final float yDistance = initialY - lp.y;

         // Set up the Folder background.
         final int finalColor = ColorUtils.setAlphaComponent(
                 Themes.getAttrColor(mContext, R.attr.folderFillColor), 255);
         final int initialColor = setColorAlphaBound(
                 finalColor, mPreviewBackground.getBackgroundAlpha());
         mFolderBackground.mutate();
         mFolderBackground.setColor(mIsOpening ? initialColor : finalColor);

         // Set up the reveal animation that clips the Folder.
         int totalOffsetX = paddingOffsetX + previewItemOffsetX;
         Rect startRect = new Rect(
                 Math.round(totalOffsetX / initialScale),
                 Math.round(paddingOffsetY / initialScale),
                 Math.round((totalOffsetX + initialSize) / initialScale),
                 Math.round((paddingOffsetY + initialSize) / initialScale));
         Rect endRect = new Rect(0, 0, lp.width, lp.height);
         float finalRadius = ResourceUtils.pxFromDp(2, mContext.getResources().getDisplayMetrics());

         // Create the animators.
         AnimatorSet a = new AnimatorSet();

         // Initialize the Folder items' text.
         PropertyResetListener colorResetListener =
                 new PropertyResetListener<>(TEXT_ALPHA_PROPERTY, 1f);
         for (BubbleTextView icon : mFolder.getItemsOnPage(mFolder.mContent.getCurrentPage())) {
             if (mIsOpening) {
                 icon.setTextVisibility(false);
             }
             ObjectAnimator anim = icon.createTextAlphaAnimator(mIsOpening);
             anim.addListener(colorResetListener);
             play(a, anim);
         }

         play(a, getAnimator(mFolder, View.TRANSLATION_X, xDistance, 0f));
         play(a, getAnimator(mFolder, View.TRANSLATION_Y, yDistance, 0f));
         play(a, getAnimator(mFolder, SCALE_PROPERTY, initialScale, finalScale));
         play(a, getAnimator(mFolderBackground, "color", initialColor, finalColor));
         play(a, mFolderIcon.mFolderName.createTextAlphaAnimator(!mIsOpening));
         play(a, getShape().createRevealAnimator(
                 mFolder, startRect, endRect, finalRadius, !mIsOpening));

         // Animate the elevation midway so that the shadow is not noticeable in the background.
         int midDuration = mDuration / 2;
         Animator z = getAnimator(mFolder, View.TRANSLATION_Z, -mFolder.getElevation(), 0);
         play(a, z, mIsOpening ? midDuration : 0, midDuration);

         a.addListener(new AnimatorListenerAdapter() {
             @Override
             public void onAnimationEnd(Animator animation) {
                 super.onAnimationEnd(animation);
                 mFolder.setTranslationX(0.0f);
                 mFolder.setTranslationY(0.0f);
                 mFolder.setTranslationZ(0.0f);
                 mFolder.setScaleX(1f);
                 mFolder.setScaleY(1f);
             }
         });

         // We set the interpolator on all current child animators here, because the preview item
         // animators may use a different interpolator.
         for (Animator animator : a.getChildAnimations()) {
             animator.setInterpolator(mFolderInterpolator);
         }

         int radiusDiff = scaledRadius - mPreviewBackground.getRadius();
         addPreviewItemAnimators(a, initialScale / scaleRelativeToDragLayer,
                 // Background can have a scaled radius in drag and drop mode, so we need to add the
                 // difference to keep the preview items centered.
                 previewItemOffsetX + radiusDiff, radiusDiff);
         return a;
     }

     /**
      * Animate the items on the current page.
      */
     private void addPreviewItemAnimators(AnimatorSet animatorSet, final float folderScale,
             int previewItemOffsetX, int previewItemOffsetY) {
         ClippedFolderIconLayoutRule rule = mFolderIcon.getLayoutRule();
         boolean isOnFirstPage = mFolder.mContent.getCurrentPage() == 0;
         final List<BubbleTextView> itemsInPreview = isOnFirstPage
                 ? mFolderIcon.getPreviewItems()
                 : mFolderIcon.getPreviewItemsOnPage(mFolder.mContent.getCurrentPage());
         final int numItemsInPreview = itemsInPreview.size();
         final int numItemsInFirstPagePreview = isOnFirstPage
                 ? numItemsInPreview : MAX_NUM_ITEMS_IN_PREVIEW;

         TimeInterpolator previewItemInterpolator = getPreviewItemInterpolator();

         ShortcutAndWidgetContainer cwc = mContent.getPageAt(0).getShortcutsAndWidgets();
         for (int i = 0; i < numItemsInPreview; ++i) {
             final BubbleTextView btv = itemsInPreview.get(i);
             CellLayout.LayoutParams btvLp = (CellLayout.LayoutParams) btv.getLayoutParams();

             // Calculate the final values in the LayoutParams.
             btvLp.isLockedToGrid = true;
             cwc.setupLp(btv);

             // Match scale of icons in the preview of the items on the first page.
             float previewScale = rule.scaleForItem(numItemsInFirstPagePreview);
             float previewSize = rule.getIconSize() * previewScale;
             float iconScale = previewSize / itemsInPreview.get(i).getIconSize();

             final float initialScale = iconScale / folderScale;
             final float finalScale = 1f;
             float scale = mIsOpening ? initialScale : finalScale;
             btv.setScaleX(scale);
             btv.setScaleY(scale);

             // Match positions of the icons in the folder with their positions in the preview
             rule.computePreviewItemDrawingParams(i, numItemsInFirstPagePreview, mTmpParams);
             // The PreviewLayoutRule assumes that the icon size takes up the entire width so we
             // offset by the actual size.
             int iconOffsetX = (int) ((btvLp.width - btv.getIconSize()) * iconScale) / 2;

             final int previewPosX =
                     (int) ((mTmpParams.transX - iconOffsetX + previewItemOffsetX) / folderScale);
             final int previewPosY = (int) ((mTmpParams.transY + previewItemOffsetY) / folderScale);

             final float xDistance = previewPosX - btvLp.x;
             final float yDistance = previewPosY - btvLp.y;

             Animator translationX = getAnimator(btv, View.TRANSLATION_X, xDistance, 0f);
             translationX.setInterpolator(previewItemInterpolator);
             play(animatorSet, translationX);

             Animator translationY = getAnimator(btv, View.TRANSLATION_Y, yDistance, 0f);
             translationY.setInterpolator(previewItemInterpolator);
             play(animatorSet, translationY);

             Animator scaleAnimator = getAnimator(btv, SCALE_PROPERTY, initialScale, finalScale);
             scaleAnimator.setInterpolator(previewItemInterpolator);
             play(animatorSet, scaleAnimator);

             if (mFolder.getItemCount() > MAX_NUM_ITEMS_IN_PREVIEW) {
                 // These delays allows the preview items to move as part of the Folder's motion,
                 // and its only necessary for large folders because of differing interpolators.
                 int delay = mIsOpening ? mDelay : mDelay * 2;
                 if (mIsOpening) {
                     translationX.setStartDelay(delay);
                     translationY.setStartDelay(delay);
                     scaleAnimator.setStartDelay(delay);
                 }
                 translationX.setDuration(translationX.getDuration() - delay);
                 translationY.setDuration(translationY.getDuration() - delay);
                 scaleAnimator.setDuration(scaleAnimator.getDuration() - delay);
             }

             animatorSet.addListener(new AnimatorListenerAdapter() {
                 @Override
                 public void onAnimationStart(Animator animation) {
                     super.onAnimationStart(animation);
                     // Necessary to initialize values here because of the start delay.
                     if (mIsOpening) {
                         btv.setTranslationX(xDistance);
                         btv.setTranslationY(yDistance);
                         btv.setScaleX(initialScale);
                         btv.setScaleY(initialScale);
                     }
                 }

                 @Override
                 public void onAnimationEnd(Animator animation) {
                     super.onAnimationEnd(animation);
                     btv.setTranslationX(0.0f);
                     btv.setTranslationY(0.0f);
                     btv.setScaleX(1f);
                     btv.setScaleY(1f);
                 }
             });
         }
     }

     private void play(AnimatorSet as, Animator a) {
         play(as, a, a.getStartDelay(), mDuration);
     }

     private void play(AnimatorSet as, Animator a, long startDelay, int duration) {
         a.setStartDelay(startDelay);
         a.setDuration(duration);
         as.play(a);
     }

     private TimeInterpolator getPreviewItemInterpolator() {
         if (mFolder.getItemCount() > MAX_NUM_ITEMS_IN_PREVIEW) {
             // With larger folders, we want the preview items to reach their final positions faster
             // (when opening) and later (when closing) so that they appear aligned with the rest of
             // the folder items when they are both visible.
             return mIsOpening
                     ? mLargeFolderPreviewItemOpenInterpolator
                     : mLargeFolderPreviewItemCloseInterpolator;
         }
         return mFolderInterpolator;
     }

     private Animator getAnimator(View view, Property property, float v1, float v2) {
         return mIsOpening
                 ? ObjectAnimator.ofFloat(view, property, v1, v2)
                 : ObjectAnimator.ofFloat(view, property, v2, v1);
     }

     private Animator getAnimator(GradientDrawable drawable, String property, int v1, int v2) {
         return mIsOpening
                 ? ObjectAnimator.ofArgb(drawable, property, v1, v2)
                 : ObjectAnimator.ofArgb(drawable, property, v2, v1);
     }
 }
	/*
	* Copyright (C) 2017 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	package com.android.launcher3.folder;

	import static com.android.launcher3.BubbleTextView.TEXT_ALPHA_PROPERTY;
	import static com.android.launcher3.LauncherAnimUtils.SCALE_PROPERTY;
	import static com.android.launcher3.folder.ClippedFolderIconLayoutRule.MAX_NUM_ITEMS_IN_PREVIEW;
	import static com.android.launcher3.graphics.IconShape.getShape;
	import static com.android.launcher3.icons.GraphicsUtils.setColorAlphaBound;

	import android.animation.Animator;
	import android.animation.AnimatorListenerAdapter;
	import android.animation.AnimatorSet;
	import android.animation.ObjectAnimator;
	import android.animation.TimeInterpolator;
	import android.content.Context;
	import android.content.res.Resources;
	import android.graphics.Rect;
	import android.graphics.drawable.GradientDrawable;
	import android.util.Property;
	import android.view.View;
	import android.view.animation.AnimationUtils;

	import androidx.core.graphics.ColorUtils;

	import com.android.launcher3.BubbleTextView;
	import com.android.launcher3.CellLayout;
	import com.android.launcher3.Launcher;
	import com.android.launcher3.R;
	import com.android.launcher3.ResourceUtils;
	import com.android.launcher3.ShortcutAndWidgetContainer;
	import com.android.launcher3.Utilities;
	import com.android.launcher3.anim.PropertyResetListener;
	import com.android.launcher3.dragndrop.DragLayer;
	import com.android.launcher3.util.Themes;

	import java.util.List;

	/**
	* Manages the opening and closing animations for a {@link Folder}.
	*
	* All of the animations are done in the Folder.
	* ie. When the user taps on the FolderIcon, we immediately hide the FolderIcon and show the Folder
	* in its place before starting the animation.
	*/
	public class FolderAnimationManager {

	private Folder mFolder;
	private FolderPagedView mContent;
	private GradientDrawable mFolderBackground;

	private FolderIcon mFolderIcon;
	private PreviewBackground mPreviewBackground;

	private Context mContext;
	private Launcher mLauncher;

	private final boolean mIsOpening;

	private final int mDuration;
	private final int mDelay;

	private final TimeInterpolator mFolderInterpolator;
	private final TimeInterpolator mLargeFolderPreviewItemOpenInterpolator;
	private final TimeInterpolator mLargeFolderPreviewItemCloseInterpolator;

	private final PreviewItemDrawingParams mTmpParams = new PreviewItemDrawingParams(0, 0, 0, 0);


	public FolderAnimationManager(Folder folder, boolean isOpening) {
	mFolder = folder;
	mContent = folder.mContent;
	mFolderBackground = (GradientDrawable) mFolder.getBackground();

	mFolderIcon = folder.mFolderIcon;
	mPreviewBackground = mFolderIcon.mBackground;

	mContext = folder.getContext();
	mLauncher = folder.mLauncher;

	mIsOpening = isOpening;

	Resources res = mContent.getResources();
	mDuration = res.getInteger(R.integer.config_materialFolderExpandDuration);
	mDelay = res.getInteger(R.integer.config_folderDelay);

	mFolderInterpolator = AnimationUtils.loadInterpolator(mContext,
	R.interpolator.folder_interpolator);
	mLargeFolderPreviewItemOpenInterpolator = AnimationUtils.loadInterpolator(mContext,
	R.interpolator.large_folder_preview_item_open_interpolator);
	mLargeFolderPreviewItemCloseInterpolator = AnimationUtils.loadInterpolator(mContext,
	R.interpolator.large_folder_preview_item_close_interpolator);
	}


	/**
	* Prepares the Folder for animating between open / closed states.
	*/
	public AnimatorSet getAnimator() {
	final DragLayer.LayoutParams lp = (DragLayer.LayoutParams) mFolder.getLayoutParams();
	ClippedFolderIconLayoutRule rule = mFolderIcon.getLayoutRule();
	final List<BubbleTextView> itemsInPreview = mFolderIcon.getPreviewItems();

	// Match position of the FolderIcon
	final Rect folderIconPos = new Rect();
	float scaleRelativeToDragLayer = mLauncher.getDragLayer()
	.getDescendantRectRelativeToSelf(mFolderIcon, folderIconPos);
	int scaledRadius = mPreviewBackground.getScaledRadius();
	float initialSize = (scaledRadius * 2) * scaleRelativeToDragLayer;

	// Match size/scale of icons in the preview
	float previewScale = rule.scaleForItem(itemsInPreview.size());
	float previewSize = rule.getIconSize() * previewScale;
	float initialScale = previewSize / itemsInPreview.get(0).getIconSize()
	* scaleRelativeToDragLayer;
	final float finalScale = 1f;
	float scale = mIsOpening ? initialScale : finalScale;
	mFolder.setScaleX(scale);
	mFolder.setScaleY(scale);
	mFolder.setPivotX(0);
	mFolder.setPivotY(0);

	// We want to create a small X offset for the preview items, so that they follow their
	// expected path to their final locations. ie. an icon should not move right, if it's final
	// location is to its left. This value is arbitrarily defined.
	int previewItemOffsetX = (int) (previewSize / 2);
	if (Utilities.isRtl(mContext.getResources())) {
	previewItemOffsetX = (int) (lp.width * initialScale - initialSize - previewItemOffsetX);
	}

	final int paddingOffsetX = (int) ((mFolder.getPaddingLeft() + mContent.getPaddingLeft())
	* initialScale);
	final int paddingOffsetY = (int) ((mFolder.getPaddingTop() + mContent.getPaddingTop())
	* initialScale);

	int initialX = folderIconPos.left + mPreviewBackground.getOffsetX() - paddingOffsetX
	- previewItemOffsetX;
	int initialY = folderIconPos.top + mPreviewBackground.getOffsetY() - paddingOffsetY;
	final float xDistance = initialX - lp.x;
	final float yDistance = initialY - lp.y;

	// Set up the Folder background.
	final int finalColor = ColorUtils.setAlphaComponent(
	Themes.getAttrColor(mContext, R.attr.folderFillColor), 255);
	final int initialColor = setColorAlphaBound(
	finalColor, mPreviewBackground.getBackgroundAlpha());
	mFolderBackground.mutate();
	mFolderBackground.setColor(mIsOpening ? initialColor : finalColor);

	// Set up the reveal animation that clips the Folder.
	int totalOffsetX = paddingOffsetX + previewItemOffsetX;
	Rect startRect = new Rect(
	Math.round(totalOffsetX / initialScale),
	Math.round(paddingOffsetY / initialScale),
	Math.round((totalOffsetX + initialSize) / initialScale),
	Math.round((paddingOffsetY + initialSize) / initialScale));
	Rect endRect = new Rect(0, 0, lp.width, lp.height);
	float finalRadius = ResourceUtils.pxFromDp(2, mContext.getResources().getDisplayMetrics());

	// Create the animators.
	AnimatorSet a = new AnimatorSet();

	// Initialize the Folder items' text.
	PropertyResetListener colorResetListener =
	new PropertyResetListener<>(TEXT_ALPHA_PROPERTY, 1f);
	for (BubbleTextView icon : mFolder.getItemsOnPage(mFolder.mContent.getCurrentPage())) {
	if (mIsOpening) {
	icon.setTextVisibility(false);
	}
	ObjectAnimator anim = icon.createTextAlphaAnimator(mIsOpening);
	anim.addListener(colorResetListener);
	play(a, anim);
	}

	play(a, getAnimator(mFolder, View.TRANSLATION_X, xDistance, 0f));
	play(a, getAnimator(mFolder, View.TRANSLATION_Y, yDistance, 0f));
	play(a, getAnimator(mFolder, SCALE_PROPERTY, initialScale, finalScale));
	play(a, getAnimator(mFolderBackground, "color", initialColor, finalColor));
	play(a, mFolderIcon.mFolderName.createTextAlphaAnimator(!mIsOpening));
	play(a, getShape().createRevealAnimator(
	mFolder, startRect, endRect, finalRadius, !mIsOpening));

	// Animate the elevation midway so that the shadow is not noticeable in the background.
	int midDuration = mDuration / 2;
	Animator z = getAnimator(mFolder, View.TRANSLATION_Z, -mFolder.getElevation(), 0);
	play(a, z, mIsOpening ? midDuration : 0, midDuration);

	a.addListener(new AnimatorListenerAdapter() {
	@Override
	public void onAnimationEnd(Animator animation) {
	super.onAnimationEnd(animation);
	mFolder.setTranslationX(0.0f);
	mFolder.setTranslationY(0.0f);
	mFolder.setTranslationZ(0.0f);
	mFolder.setScaleX(1f);
	mFolder.setScaleY(1f);
	}
	});

	// We set the interpolator on all current child animators here, because the preview item
	// animators may use a different interpolator.
	for (Animator animator : a.getChildAnimations()) {
	animator.setInterpolator(mFolderInterpolator);
	}

	int radiusDiff = scaledRadius - mPreviewBackground.getRadius();
	addPreviewItemAnimators(a, initialScale / scaleRelativeToDragLayer,
	// Background can have a scaled radius in drag and drop mode, so we need to add the
	// difference to keep the preview items centered.
	previewItemOffsetX + radiusDiff, radiusDiff);
	return a;
	}

	/**
	* Animate the items on the current page.
	*/
	private void addPreviewItemAnimators(AnimatorSet animatorSet, final float folderScale,
	int previewItemOffsetX, int previewItemOffsetY) {
	ClippedFolderIconLayoutRule rule = mFolderIcon.getLayoutRule();
	boolean isOnFirstPage = mFolder.mContent.getCurrentPage() == 0;
	final List<BubbleTextView> itemsInPreview = isOnFirstPage
	? mFolderIcon.getPreviewItems()
	: mFolderIcon.getPreviewItemsOnPage(mFolder.mContent.getCurrentPage());
	final int numItemsInPreview = itemsInPreview.size();
	final int numItemsInFirstPagePreview = isOnFirstPage
	? numItemsInPreview : MAX_NUM_ITEMS_IN_PREVIEW;

	TimeInterpolator previewItemInterpolator = getPreviewItemInterpolator();

	ShortcutAndWidgetContainer cwc = mContent.getPageAt(0).getShortcutsAndWidgets();
	for (int i = 0; i < numItemsInPreview; ++i) {
	final BubbleTextView btv = itemsInPreview.get(i);
	CellLayout.LayoutParams btvLp = (CellLayout.LayoutParams) btv.getLayoutParams();

	// Calculate the final values in the LayoutParams.
	btvLp.isLockedToGrid = true;
	cwc.setupLp(btv);

	// Match scale of icons in the preview of the items on the first page.
	float previewScale = rule.scaleForItem(numItemsInFirstPagePreview);
	float previewSize = rule.getIconSize() * previewScale;
	float iconScale = previewSize / itemsInPreview.get(i).getIconSize();

	final float initialScale = iconScale / folderScale;
	final float finalScale = 1f;
	float scale = mIsOpening ? initialScale : finalScale;
	btv.setScaleX(scale);
	btv.setScaleY(scale);

	// Match positions of the icons in the folder with their positions in the preview
	rule.computePreviewItemDrawingParams(i, numItemsInFirstPagePreview, mTmpParams);
	// The PreviewLayoutRule assumes that the icon size takes up the entire width so we
	// offset by the actual size.
	int iconOffsetX = (int) ((btvLp.width - btv.getIconSize()) * iconScale) / 2;

	final int previewPosX =
	(int) ((mTmpParams.transX - iconOffsetX + previewItemOffsetX) / folderScale);
	final int previewPosY = (int) ((mTmpParams.transY + previewItemOffsetY) / folderScale);

	final float xDistance = previewPosX - btvLp.x;
	final float yDistance = previewPosY - btvLp.y;

	Animator translationX = getAnimator(btv, View.TRANSLATION_X, xDistance, 0f);
	translationX.setInterpolator(previewItemInterpolator);
	play(animatorSet, translationX);

	Animator translationY = getAnimator(btv, View.TRANSLATION_Y, yDistance, 0f);
	translationY.setInterpolator(previewItemInterpolator);
	play(animatorSet, translationY);

	Animator scaleAnimator = getAnimator(btv, SCALE_PROPERTY, initialScale, finalScale);
	scaleAnimator.setInterpolator(previewItemInterpolator);
	play(animatorSet, scaleAnimator);

	if (mFolder.getItemCount() > MAX_NUM_ITEMS_IN_PREVIEW) {
	// These delays allows the preview items to move as part of the Folder's motion,
	// and its only necessary for large folders because of differing interpolators.
	int delay = mIsOpening ? mDelay : mDelay * 2;
	if (mIsOpening) {
	translationX.setStartDelay(delay);
	translationY.setStartDelay(delay);
	scaleAnimator.setStartDelay(delay);
	}
	translationX.setDuration(translationX.getDuration() - delay);
	translationY.setDuration(translationY.getDuration() - delay);
	scaleAnimator.setDuration(scaleAnimator.getDuration() - delay);
	}

	animatorSet.addListener(new AnimatorListenerAdapter() {
	@Override
	public void onAnimationStart(Animator animation) {
	super.onAnimationStart(animation);
	// Necessary to initialize values here because of the start delay.
	if (mIsOpening) {
	btv.setTranslationX(xDistance);
	btv.setTranslationY(yDistance);
	btv.setScaleX(initialScale);
	btv.setScaleY(initialScale);
	}
	}

	@Override
	public void onAnimationEnd(Animator animation) {
	super.onAnimationEnd(animation);
	btv.setTranslationX(0.0f);
	btv.setTranslationY(0.0f);
	btv.setScaleX(1f);
	btv.setScaleY(1f);
	}
	});
	}
	}

	private void play(AnimatorSet as, Animator a) {
	play(as, a, a.getStartDelay(), mDuration);
	}

	private void play(AnimatorSet as, Animator a, long startDelay, int duration) {
	a.setStartDelay(startDelay);
	a.setDuration(duration);
	as.play(a);
	}

	private TimeInterpolator getPreviewItemInterpolator() {
	if (mFolder.getItemCount() > MAX_NUM_ITEMS_IN_PREVIEW) {
	// With larger folders, we want the preview items to reach their final positions faster
	// (when opening) and later (when closing) so that they appear aligned with the rest of
	// the folder items when they are both visible.
	return mIsOpening
	? mLargeFolderPreviewItemOpenInterpolator
	: mLargeFolderPreviewItemCloseInterpolator;
	}
	return mFolderInterpolator;
	}

	private Animator getAnimator(View view, Property property, float v1, float v2) {
	return mIsOpening
	? ObjectAnimator.ofFloat(view, property, v1, v2)
	: ObjectAnimator.ofFloat(view, property, v2, v1);
	}

	private Animator getAnimator(GradientDrawable drawable, String property, int v1, int v2) {
	return mIsOpening
	? ObjectAnimator.ofArgb(drawable, property, v1, v2)
	: ObjectAnimator.ofArgb(drawable, property, v2, v1);
	}
	}