Move the PreviewItem drawing/animation logic to PreviewItemManager.

We want this refactor in O-DR since we will be adding more animations:
- closing from a non-first page (ag/2455887 b/36022592)
- new on-drop animations *if we end up removing the permutation logic.

Bug: 36022592
Change-Id: I82b8f5f5033d4fd9bd50fbe414b0fb721891d043

4 files changed, 261 insertions, 196 deletions

diff --git a/src/com/android/launcher3/folder/Folder.java b/src/com/android/launcher3/folder/Folder.java
index f68b394c1..afbf9f2a2 100644
--- a/src/com/android/launcher3/folder/Folder.java
+++ b/src/com/android/launcher3/folder/Folder.java
@@ -1280,7 +1280,7 @@ public class Folder extends AbstractFloatingView implements DragSource, View.OnC
         };
         View finalChild = mContent.getLastItem();
         if (finalChild != null) {
-            mFolderIcon.performDestroyAnimation(finalChild, onCompleteRunnable);
+            mFolderIcon.performDestroyAnimation(onCompleteRunnable);
         } else {
             onCompleteRunnable.run();
         }
diff --git a/src/com/android/launcher3/folder/FolderIcon.java b/src/com/android/launcher3/folder/FolderIcon.java
index 3a0e71fa5..7fdacc094 100644
--- a/src/com/android/launcher3/folder/FolderIcon.java
+++ b/src/com/android/launcher3/folder/FolderIcon.java
@@ -37,7 +37,6 @@ import android.view.ViewGroup;
 import android.view.animation.AccelerateInterpolator;
 import android.view.animation.DecelerateInterpolator;
 import android.widget.FrameLayout;
-import android.widget.TextView;
 
 import com.android.launcher3.Alarm;
 import com.android.launcher3.AppInfo;
@@ -71,6 +70,8 @@ import com.android.launcher3.widget.PendingAddShortcutInfo;
 import java.util.ArrayList;
 import java.util.List;
 
+import static com.android.launcher3.folder.PreviewItemManager.INITIAL_ITEM_ANIMATION_DURATION;
+
 /**
  * An icon that can appear on in the workspace representing an {@link Folder}.
  */
@@ -87,9 +88,7 @@ public class FolderIcon extends FrameLayout implements FolderListener {
     private CheckLongPressHelper mLongPressHelper;
     private StylusEventHelper mStylusEventHelper;
 
-    private static final int DROP_IN_ANIMATION_DURATION = 400;
-    private static final int INITIAL_ITEM_ANIMATION_DURATION = 350;
-    private static final int FINAL_ITEM_ANIMATION_DURATION = 200;
+    static final int DROP_IN_ANIMATION_DURATION = 400;
 
     // Flag whether the folder should open itself when an item is dragged over is enabled.
     public static final boolean SPRING_LOADING_ENABLED = true;
@@ -99,27 +98,19 @@ public class FolderIcon extends FrameLayout implements FolderListener {
 
     @Thunk BubbleTextView mFolderName;
 
-    // These variables are all associated with the drawing of the preview; they are stored
-    // as member variables for shared usage and to avoid computation on each frame
-    private float mIntrinsicIconSize = -1;
-    private int mTotalWidth = -1;
-    private int mPrevTopPadding = -1;
-
     PreviewBackground mBackground = new PreviewBackground();
     private boolean mBackgroundIsVisible = true;
 
-    private PreviewLayoutRule mPreviewLayoutRule;
+    FolderIconPreviewVerifier mPreviewVerifier;
+    PreviewLayoutRule mPreviewLayoutRule;
+    private PreviewItemManager mPreviewItemManager;
+    private PreviewItemDrawingParams mTmpParams = new PreviewItemDrawingParams(0, 0, 0, 0);
 
     boolean mAnimating = false;
     private Rect mTempBounds = new Rect();
 
     private float mSlop;
 
-    FolderIconPreviewVerifier mPreviewVerifier;
-    private PreviewItemDrawingParams mTmpParams = new PreviewItemDrawingParams(0, 0, 0, 0);
-    private ArrayList<PreviewItemDrawingParams> mDrawingParams = new ArrayList<>();
-    private Drawable mReferenceDrawable = null;
-
     private Alarm mOpenAlarm = new Alarm();
 
     private FolderBadgeInfo mBadgeInfo = new FolderBadgeInfo();
@@ -158,6 +149,7 @@ public class FolderIcon extends FrameLayout implements FolderListener {
                 new StackFolderIconLayoutRule() :
                 new ClippedFolderIconLayoutRule();
         mSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();
+        mPreviewItemManager = new PreviewItemManager(this);
     }
 
     public static FolderIcon fromXml(int resId, Launcher launcher, ViewGroup group,
@@ -213,7 +205,7 @@ public class FolderIcon extends FrameLayout implements FolderListener {
     private void setFolder(Folder folder) {
         mFolder = folder;
         mPreviewVerifier = new FolderIconPreviewVerifier(mLauncher.getDeviceProfile().inv);
-        updateItemDrawingParams(false);
+        mPreviewItemManager.updateItemDrawingParams(false);
     }
 
     private boolean willAcceptItem(ItemInfo item) {
@@ -254,40 +246,28 @@ public class FolderIcon extends FrameLayout implements FolderListener {
         }
     };
 
-    public Drawable prepareCreate(final View destView) {
-        Drawable animateDrawable = ((TextView) destView).getCompoundDrawables()[1];
-        computePreviewDrawingParams(animateDrawable.getIntrinsicWidth(),
-                destView.getMeasuredWidth());
-        return animateDrawable;
+    public Drawable prepareCreateAnimation(final View destView) {
+        return mPreviewItemManager.prepareCreateAnimation(destView);
     }
 
     public void performCreateAnimation(final ShortcutInfo destInfo, final View destView,
             final ShortcutInfo srcInfo, final DragView srcView, Rect dstRect,
             float scaleRelativeToDragLayer, Runnable postAnimationRunnable) {
-
-        // These correspond two the drawable and view that the icon was dropped _onto_
-        Drawable animateDrawable = prepareCreate(destView);
-
-        mReferenceDrawable = animateDrawable;
-
+        prepareCreateAnimation(destView);
         addItem(destInfo);
         // This will animate the first item from it's position as an icon into its
         // position as the first item in the preview
-        animateFirstItem(animateDrawable, INITIAL_ITEM_ANIMATION_DURATION, false, null);
+        mPreviewItemManager.createFirstItemAnimation(false /* reverse */, null)
+                .start();
 
         // This will animate the dragView (srcView) into the new folder
         onDrop(srcInfo, srcView, dstRect, scaleRelativeToDragLayer, 1, postAnimationRunnable);
     }
 
-    public void performDestroyAnimation(final View finalView, Runnable onCompleteRunnable) {
-        Drawable animateDrawable = ((TextView) finalView).getCompoundDrawables()[1];
-        computePreviewDrawingParams(animateDrawable.getIntrinsicWidth(),
-                finalView.getMeasuredWidth());
-
-        // This will animate the first item from it's position as an icon into its
-        // position as the first item in the preview
-        animateFirstItem(animateDrawable, FINAL_ITEM_ANIMATION_DURATION, true,
-                onCompleteRunnable);
+    public void performDestroyAnimation(Runnable onCompleteRunnable) {
+        // This will animate the final item in the preview to be full size.
+        mPreviewItemManager.createFirstItemAnimation(true /* reverse */, onCompleteRunnable)
+                .start();
     }
 
     public void onDragExit() {
@@ -296,7 +276,7 @@ public class FolderIcon extends FrameLayout implements FolderListener {
     }
 
     private void onDrop(final ShortcutInfo item, DragView animateView, Rect finalRect,
-            float scaleRelativeToDragLayer, int index, Runnable postAnimationRunnable) {
+            float scaleRelativeToDragLayer, final int index, Runnable postAnimationRunnable) {
         item.cellX = -1;
         item.cellY = -1;
 
@@ -342,12 +322,10 @@ public class FolderIcon extends FrameLayout implements FolderListener {
             addItem(item);
             mFolder.hideItem(item);
 
-            final PreviewItemDrawingParams params = index < mDrawingParams.size() ?
-                    mDrawingParams.get(index) : null;
-            if (params != null) params.hidden = true;
+            mPreviewItemManager.hidePreviewItem(index, true);
             postDelayed(new Runnable() {
                 public void run() {
-                    if (params != null) params.hidden = false;
+                    mPreviewItemManager.hidePreviewItem(index, false);
                     mFolder.showItem(item);
                     invalidate();
                 }
@@ -369,25 +347,6 @@ public class FolderIcon extends FrameLayout implements FolderListener {
         onDrop(item, d.dragView, null, 1.0f, mInfo.contents.size(), d.postAnimationRunnable);
     }
 
-    private void computePreviewDrawingParams(int drawableSize, int totalSize) {
-        if (mIntrinsicIconSize != drawableSize || mTotalWidth != totalSize ||
-                mPrevTopPadding != getPaddingTop()) {
-            mIntrinsicIconSize = drawableSize;
-            mTotalWidth = totalSize;
-            mPrevTopPadding = getPaddingTop();
-
-            mBackground.setup(mLauncher, this, mTotalWidth, getPaddingTop());
-            mPreviewLayoutRule.init(mBackground.previewSize, mIntrinsicIconSize,
-                    Utilities.isRtl(getResources()));
-
-            updateItemDrawingParams(false);
-        }
-    }
-
-    private void computePreviewDrawingParams(Drawable d) {
-        computePreviewDrawingParams(d.getIntrinsicWidth(), getMeasuredWidth());
-    }
-
     public void setBadgeInfo(FolderBadgeInfo badgeInfo) {
         updateBadgeScale(mBadgeInfo.hasBadge(), badgeInfo.hasBadge());
         mBadgeInfo = badgeInfo;
@@ -421,56 +380,21 @@ public class FolderIcon extends FrameLayout implements FolderListener {
     }
 
     private float getLocalCenterForIndex(int index, int curNumItems, int[] center) {
-        mTmpParams = computePreviewItemDrawingParams(
+        mTmpParams = mPreviewItemManager.computePreviewItemDrawingParams(
                 Math.min(mPreviewLayoutRule.maxNumItems(), index), curNumItems, mTmpParams);
 
         mTmpParams.transX += mBackground.basePreviewOffsetX;
         mTmpParams.transY += mBackground.basePreviewOffsetY;
-        float offsetX = mTmpParams.transX + (mTmpParams.scale * mIntrinsicIconSize) / 2;
-        float offsetY = mTmpParams.transY + (mTmpParams.scale * mIntrinsicIconSize) / 2;
+
+        float intrinsicIconSize = mPreviewItemManager.getIntrinsicIconSize();
+        float offsetX = mTmpParams.transX + (mTmpParams.scale * intrinsicIconSize) / 2;
+        float offsetY = mTmpParams.transY + (mTmpParams.scale * intrinsicIconSize) / 2;
 
         center[0] = Math.round(offsetX);
         center[1] = Math.round(offsetY);
         return mTmpParams.scale;
     }
 
-    PreviewItemDrawingParams computePreviewItemDrawingParams(int index, int curNumItems,
-            PreviewItemDrawingParams params) {
-        // We use an index of -1 to represent an icon on the workspace for the destroy and
-        // create animations
-        if (index == -1) {
-            return getFinalIconParams(params);
-        }
-        return mPreviewLayoutRule.computePreviewItemDrawingParams(index, curNumItems, params);
-    }
-
-    private PreviewItemDrawingParams getFinalIconParams(PreviewItemDrawingParams params) {
-        float iconSize = mLauncher.getDeviceProfile().iconSizePx;
-
-        final float scale = iconSize / mReferenceDrawable.getIntrinsicWidth();
-        final float trans = (mBackground.previewSize - iconSize) / 2;
-
-        params.update(trans, trans, scale);
-        return params;
-    }
-
-    private void drawPreviewItem(Canvas canvas, PreviewItemDrawingParams params) {
-        canvas.save(Canvas.MATRIX_SAVE_FLAG);
-        canvas.translate(params.transX, params.transY);
-        canvas.scale(params.scale, params.scale);
-        Drawable d = params.drawable;
-
-        if (d != null) {
-            Rect bounds = d.getBounds();
-            canvas.save();
-            canvas.translate(-bounds.left, -bounds.top);
-            canvas.scale(mIntrinsicIconSize / bounds.width(), mIntrinsicIconSize / bounds.height());
-            d.draw(canvas);
-            canvas.restore();
-        }
-        canvas.restore();
-    }
-
     public void setFolderBackground(PreviewBackground bg) {
         mBackground = bg;
         mBackground.setInvalidateDelegate(this);
@@ -487,10 +411,6 @@ public class FolderIcon extends FrameLayout implements FolderListener {
 
         if (!mBackgroundIsVisible) return;
 
-        if (mReferenceDrawable != null) {
-            computePreviewDrawingParams(mReferenceDrawable);
-        }
-
         if (!mBackground.drawingDelegated()) {
             mBackground.drawBackground(canvas);
         }
@@ -512,14 +432,7 @@ public class FolderIcon extends FrameLayout implements FolderListener {
 
         // The items are drawn in coordinates relative to the preview offset
         canvas.translate(mBackground.basePreviewOffsetX, mBackground.basePreviewOffsetY);
-
-        // The first item should be drawn last (ie. on top of later items)
-        for (int i = mDrawingParams.size() - 1; i >= 0; i--) {
-            PreviewItemDrawingParams p = mDrawingParams.get(i);
-            if (!p.hidden) {
-                drawPreviewItem(canvas, p);
-            }
-        }
+        mPreviewItemManager.draw(canvas);
         canvas.translate(-mBackground.basePreviewOffsetX, -mBackground.basePreviewOffsetY);
 
         if (mPreviewLayoutRule.clipToBackground() && canvas.isHardwareAccelerated()) {
@@ -546,19 +459,6 @@ public class FolderIcon extends FrameLayout implements FolderListener {
         }
     }
 
-    private void animateFirstItem(final Drawable d, int duration, final boolean reverse,
-            final Runnable onCompleteRunnable) {
-        FolderPreviewItemAnim anim;
-        if (!reverse) {
-            anim = new FolderPreviewItemAnim(this, mDrawingParams.get(0), -1, -1, 0, 2, duration,
-                    onCompleteRunnable);
-        } else {
-            anim = new FolderPreviewItemAnim(this, mDrawingParams.get(0), 0, 2, -1, -1, duration,
-                    onCompleteRunnable);
-        }
-        anim.start();
-    }
-
     public void setTextVisible(boolean visible) {
         if (visible) {
             mFolderName.setVisibility(VISIBLE);
@@ -591,63 +491,12 @@ public class FolderIcon extends FrameLayout implements FolderListener {
 
     @Override
     protected boolean verifyDrawable(@NonNull Drawable who) {
-        for (int i = 0; i < mDrawingParams.size(); i++) {
-            if (mDrawingParams.get(i).drawable == who) {
-                return true;
-            }
-        }
-        return super.verifyDrawable(who);
-    }
-
-    private void updateItemDrawingParams(boolean animate) {
-        List<BubbleTextView> items = getItemsToDisplay();
-        int nItemsInPreview = items.size();
-
-        int prevNumItems = mDrawingParams.size();
-
-        // We adjust the size of the list to match the number of items in the preview
-        while (nItemsInPreview < mDrawingParams.size()) {
-            mDrawingParams.remove(mDrawingParams.size() - 1);
-        }
-        while (nItemsInPreview > mDrawingParams.size()) {
-            mDrawingParams.add(new PreviewItemDrawingParams(0, 0, 0, 0));
-        }
-
-        for (int i = 0; i < mDrawingParams.size(); i++) {
-            PreviewItemDrawingParams p = mDrawingParams.get(i);
-            p.drawable = items.get(i).getCompoundDrawables()[1];
-
-            if (p.drawable != null && !mFolder.isOpen()) {
-                // Set the callback to FolderIcon as it is responsible to drawing the icon. The
-                // callback will be release when the folder is opened.
-                p.drawable.setCallback(this);
-            }
-
-            if (!animate || FeatureFlags.LAUNCHER3_LEGACY_FOLDER_ICON) {
-                computePreviewItemDrawingParams(i, nItemsInPreview, p);
-                if (mReferenceDrawable == null) {
-                    mReferenceDrawable = p.drawable;
-                }
-            } else {
-                FolderPreviewItemAnim anim = new FolderPreviewItemAnim(this, p, i, prevNumItems, i,
-                        nItemsInPreview, DROP_IN_ANIMATION_DURATION, null);
-
-                if (p.anim != null) {
-                    if (p.anim.hasEqualFinalState(anim)) {
-                        // do nothing, let the current animation finish
-                        continue;
-                    }
-                    p.anim.cancel();
-                }
-                p.anim = anim;
-                p.anim.start();
-            }
-        }
+        return mPreviewItemManager.verifyDrawable(who) || super.verifyDrawable(who);
     }
 
     @Override
     public void onItemsChanged(boolean animate) {
-        updateItemDrawingParams(animate);
+        mPreviewItemManager.updateItemDrawingParams(animate);
         invalidate();
         requestLayout();
     }
diff --git a/src/com/android/launcher3/folder/FolderPreviewItemAnim.java b/src/com/android/launcher3/folder/FolderPreviewItemAnim.java
index 0da7c5cb1..be075bc9a 100644
--- a/src/com/android/launcher3/folder/FolderPreviewItemAnim.java
+++ b/src/com/android/launcher3/folder/FolderPreviewItemAnim.java
@@ -25,16 +25,16 @@ import com.android.launcher3.LauncherAnimUtils;
  * Animates a Folder preview item.
  */
 class FolderPreviewItemAnim {
+
+    private static PreviewItemDrawingParams sTmpParams = new PreviewItemDrawingParams(0, 0, 0, 0);
+
     private ValueAnimator mValueAnimator;
 
     float finalScale;
     float finalTransX;
     float finalTransY;
 
-    private PreviewItemDrawingParams mTmpParams = new PreviewItemDrawingParams(0, 0, 0, 0);
-
     /**
-     * @param folderIcon The FolderIcon this preview will be drawn in.
      * @param params layout params to animate
      * @param index0 original index of the item to be animated
      * @param items0 original number of items in the preview
@@ -43,20 +43,20 @@ class FolderPreviewItemAnim {
      * @param duration duration in ms of the animation
      * @param onCompleteRunnable runnable to execute upon animation completion
      */
-    FolderPreviewItemAnim(final FolderIcon folderIcon, final PreviewItemDrawingParams params,
-            int index0, int items0, int index1, int items1, int duration,
-            final Runnable onCompleteRunnable) {
-        folderIcon.computePreviewItemDrawingParams(index1, items1, mTmpParams);
+    FolderPreviewItemAnim(final PreviewItemManager previewItemManager,
+            final PreviewItemDrawingParams params, int index0, int items0, int index1, int items1,
+            int duration, final Runnable onCompleteRunnable) {
+        previewItemManager.computePreviewItemDrawingParams(index1, items1, sTmpParams);
 
-        finalScale = mTmpParams.scale;
-        finalTransX = mTmpParams.transX;
-        finalTransY = mTmpParams.transY;
+        finalScale = sTmpParams.scale;
+        finalTransX = sTmpParams.transX;
+        finalTransY = sTmpParams.transY;
 
-        folderIcon.computePreviewItemDrawingParams(index0, items0, mTmpParams);
+        previewItemManager.computePreviewItemDrawingParams(index0, items0, sTmpParams);
 
-        final float scale0 = mTmpParams.scale;
-        final float transX0 = mTmpParams.transX;
-        final float transY0 = mTmpParams.transY;
+        final float scale0 = sTmpParams.scale;
+        final float transX0 = sTmpParams.transX;
+        final float transY0 = sTmpParams.transY;
 
         mValueAnimator = LauncherAnimUtils.ofFloat(0f, 1.0f);
         mValueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener(){
@@ -66,7 +66,7 @@ class FolderPreviewItemAnim {
                 params.transX = transX0 + progress * (finalTransX - transX0);
                 params.transY = transY0 + progress * (finalTransY - transY0);
                 params.scale = scale0 + progress * (finalScale - scale0);
-                folderIcon.invalidate();
+                previewItemManager.onParamsChanged();
             }
         });
         mValueAnimator.addListener(new AnimatorListenerAdapter() {
diff --git a/src/com/android/launcher3/folder/PreviewItemManager.java b/src/com/android/launcher3/folder/PreviewItemManager.java
new file mode 100644
index 000000000..2524a6d82
--- /dev/null
+++ b/src/com/android/launcher3/folder/PreviewItemManager.java
@@ -0,0 +1,216 @@
+/*
+ * 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 android.graphics.Canvas;
+import android.graphics.Rect;
+import android.graphics.drawable.Drawable;
+import android.support.annotation.NonNull;
+import android.view.View;
+import android.widget.TextView;
+
+import com.android.launcher3.BubbleTextView;
+import com.android.launcher3.Utilities;
+import com.android.launcher3.config.FeatureFlags;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import static com.android.launcher3.folder.FolderIcon.DROP_IN_ANIMATION_DURATION;
+
+/**
+ * Manages the drawing and animations of {@link PreviewItemDrawingParams} for a {@link FolderIcon}.
+ */
+public class PreviewItemManager {
+
+    private FolderIcon mIcon;
+
+    // These variables are all associated with the drawing of the preview; they are stored
+    // as member variables for shared usage and to avoid computation on each frame
+    private float mIntrinsicIconSize = -1;
+    private int mTotalWidth = -1;
+    private int mPrevTopPadding = -1;
+    private Drawable mReferenceDrawable = null;
+
+    // These hold the first page preview items
+    private ArrayList<PreviewItemDrawingParams> mFirstPageParams = new ArrayList<>();
+
+    static final int INITIAL_ITEM_ANIMATION_DURATION = 350;
+    private static final int FINAL_ITEM_ANIMATION_DURATION = 200;
+
+    public PreviewItemManager(FolderIcon icon) {
+        mIcon = icon;
+    }
+
+    /**
+     * @param reverse If true, animates the final item in the preview to be full size. If false,
+     *                animates the first item to its position in the preview.
+     */
+    public FolderPreviewItemAnim createFirstItemAnimation(final boolean reverse,
+            final Runnable onCompleteRunnable) {
+        return reverse
+                ? new FolderPreviewItemAnim(this, mFirstPageParams.get(0), 0, 2, -1, -1,
+                        FINAL_ITEM_ANIMATION_DURATION, onCompleteRunnable)
+                : new FolderPreviewItemAnim(this, mFirstPageParams.get(0), -1, -1, 0, 2,
+                        INITIAL_ITEM_ANIMATION_DURATION, onCompleteRunnable);
+    }
+
+    Drawable prepareCreateAnimation(final View destView) {
+        Drawable animateDrawable = ((TextView) destView).getCompoundDrawables()[1];
+        computePreviewDrawingParams(animateDrawable.getIntrinsicWidth(),
+                destView.getMeasuredWidth());
+        mReferenceDrawable = animateDrawable;
+        return animateDrawable;
+    }
+
+    private void computePreviewDrawingParams(Drawable d) {
+        computePreviewDrawingParams(d.getIntrinsicWidth(), mIcon.getMeasuredWidth());
+    }
+
+    private void computePreviewDrawingParams(int drawableSize, int totalSize) {
+        if (mIntrinsicIconSize != drawableSize || mTotalWidth != totalSize ||
+                mPrevTopPadding != mIcon.getPaddingTop()) {
+            mIntrinsicIconSize = drawableSize;
+            mTotalWidth = totalSize;
+            mPrevTopPadding = mIcon.getPaddingTop();
+
+            mIcon.mBackground.setup(mIcon.mLauncher, mIcon, mTotalWidth, mIcon.getPaddingTop());
+            mIcon.mPreviewLayoutRule.init(mIcon.mBackground.previewSize, mIntrinsicIconSize,
+                    Utilities.isRtl(mIcon.getResources()));
+
+            updateItemDrawingParams(false);
+        }
+    }
+
+    PreviewItemDrawingParams computePreviewItemDrawingParams(int index, int curNumItems,
+            PreviewItemDrawingParams params) {
+        // We use an index of -1 to represent an icon on the workspace for the destroy and
+        // create animations
+        if (index == -1) {
+            return getFinalIconParams(params);
+        }
+        return mIcon.mPreviewLayoutRule.computePreviewItemDrawingParams(index, curNumItems, params);
+    }
+
+    private PreviewItemDrawingParams getFinalIconParams(PreviewItemDrawingParams params) {
+        float iconSize = mIcon.mLauncher.getDeviceProfile().iconSizePx;
+
+        final float scale = iconSize / mReferenceDrawable.getIntrinsicWidth();
+        final float trans = (mIcon.mBackground.previewSize - iconSize) / 2;
+
+        params.update(trans, trans, scale);
+        return params;
+    }
+
+    public void draw(Canvas canvas) {
+        computePreviewDrawingParams(mReferenceDrawable);
+        // The first item should be drawn last (ie. on top of later items)
+        for (int i = mFirstPageParams.size() - 1; i >= 0; i--) {
+            PreviewItemDrawingParams p = mFirstPageParams.get(i);
+            if (!p.hidden) {
+                drawPreviewItem(canvas, p);
+            }
+        }
+    }
+
+    public void onParamsChanged() {
+        mIcon.invalidate();
+    }
+
+    private void drawPreviewItem(Canvas canvas, PreviewItemDrawingParams params) {
+        canvas.save(Canvas.MATRIX_SAVE_FLAG);
+        canvas.translate(params.transX, params.transY);
+        canvas.scale(params.scale, params.scale);
+        Drawable d = params.drawable;
+
+        if (d != null) {
+            Rect bounds = d.getBounds();
+            canvas.save();
+            canvas.translate(-bounds.left, -bounds.top);
+            canvas.scale(mIntrinsicIconSize / bounds.width(), mIntrinsicIconSize / bounds.height());
+            d.draw(canvas);
+            canvas.restore();
+        }
+        canvas.restore();
+    }
+
+    public void hidePreviewItem(int index, boolean hidden) {
+        PreviewItemDrawingParams params = index < mFirstPageParams.size() ?
+                mFirstPageParams.get(index) : null;
+        if (params != null) {
+            params.hidden = hidden;
+        }
+    }
+
+    void updateItemDrawingParams(boolean animate) {
+        List<BubbleTextView> items = mIcon.getItemsToDisplay();
+        int numItemsInPreview = items.size();
+        int prevNumItems = mFirstPageParams.size();
+
+        // We adjust the size of the list to match the number of items in the preview
+        while (numItemsInPreview < mFirstPageParams.size()) {
+            mFirstPageParams.remove(mFirstPageParams.size() - 1);
+        }
+        while (numItemsInPreview > mFirstPageParams.size()) {
+            mFirstPageParams.add(new PreviewItemDrawingParams(0, 0, 0, 0));
+        }
+
+        for (int i = 0; i < mFirstPageParams.size(); i++) {
+            PreviewItemDrawingParams p = mFirstPageParams.get(i);
+            p.drawable = items.get(i).getCompoundDrawables()[1];
+
+            if (p.drawable != null && !mIcon.mFolder.isOpen()) {
+                // Set the callback to FolderIcon as it is responsible to drawing the icon. The
+                // callback will be released when the folder is opened.
+                p.drawable.setCallback(mIcon);
+            }
+
+            if (!animate || FeatureFlags.LAUNCHER3_LEGACY_FOLDER_ICON) {
+                computePreviewItemDrawingParams(i, numItemsInPreview, p);
+                if (mReferenceDrawable == null) {
+                    mReferenceDrawable = p.drawable;
+                }
+            } else {
+                FolderPreviewItemAnim anim = new FolderPreviewItemAnim(this, p, i, prevNumItems, i,
+                        numItemsInPreview, DROP_IN_ANIMATION_DURATION, null);
+
+                if (p.anim != null) {
+                    if (p.anim.hasEqualFinalState(anim)) {
+                        // do nothing, let the current animation finish
+                        continue;
+                    }
+                    p.anim.cancel();
+                }
+                p.anim = anim;
+                p.anim.start();
+            }
+        }
+    }
+
+    boolean verifyDrawable(@NonNull Drawable who) {
+        for (int i = 0; i < mFirstPageParams.size(); i++) {
+            if (mFirstPageParams.get(i).drawable == who) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    float getIntrinsicIconSize() {
+        return mIntrinsicIconSize;
+    }
+}