Merge "Adds back gesture recognition to Sandbox." into ub-launcher3-master
diff --git a/quickstep/res/layout/back_gesture_tutorial_fragment.xml b/quickstep/res/layout/back_gesture_tutorial_fragment.xml
index 294e46e..d8c25bd 100644
--- a/quickstep/res/layout/back_gesture_tutorial_fragment.xml
+++ b/quickstep/res/layout/back_gesture_tutorial_fragment.xml
@@ -16,9 +16,7 @@
 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
-    android:layerType="software"
     android:background="@color/back_gesture_tutorial_background_color">
-    <!--The layout is rendered on the software layer to avoid b/136158117-->
 
     <ImageView
         android:id="@+id/back_gesture_tutorial_fragment_hand_coaching"
diff --git a/quickstep/res/values/colors.xml b/quickstep/res/values/colors.xml
new file mode 100644
index 0000000..3583676
--- /dev/null
+++ b/quickstep/res/values/colors.xml
@@ -0,0 +1,18 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (C) 2020 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.
+-->
+<resources>
+    <color name="back_arrow_color_dark">#99000000</color>
+</resources>
\ No newline at end of file
diff --git a/quickstep/src/com/android/quickstep/interaction/BackGestureTutorialController.java b/quickstep/src/com/android/quickstep/interaction/BackGestureTutorialController.java
index 3fe91a3..5c2e992 100644
--- a/quickstep/src/com/android/quickstep/interaction/BackGestureTutorialController.java
+++ b/quickstep/src/com/android/quickstep/interaction/BackGestureTutorialController.java
@@ -25,6 +25,7 @@
 import com.android.launcher3.R;
 import com.android.quickstep.interaction.BackGestureTutorialFragment.TutorialStep;
 import com.android.quickstep.interaction.BackGestureTutorialFragment.TutorialType;
+import com.android.quickstep.interaction.EdgeBackGestureHandler.BackGestureResult;
 
 import java.util.Optional;
 
@@ -79,21 +80,33 @@
         mHandCoachingAnimation.stop();
     }
 
-    void onGestureDetected() {
-        hideHandCoachingAnimation();
-
-        if (mTutorialStep == TutorialStep.CONFIRM) {
+    void onGestureAttempted(BackGestureResult result) {
+        if (mTutorialStep == TutorialStep.CONFIRM
+                && (result == BackGestureResult.BACK_COMPLETED_FROM_LEFT
+                    || result == BackGestureResult.BACK_COMPLETED_FROM_RIGHT)) {
             mFragment.closeTutorial();
             return;
         }
 
-        if (mTutorialTypeInfo.get().getTutorialType() == TutorialType.RIGHT_EDGE_BACK_NAVIGATION) {
-            mFragment.changeController(TutorialStep.ENGAGED,
-                    TutorialType.LEFT_EDGE_BACK_NAVIGATION);
+        if (!mTutorialTypeInfo.isPresent()) {
             return;
         }
 
-        mFragment.changeController(TutorialStep.CONFIRM);
+        switch (mTutorialTypeInfo.get().getTutorialType()) {
+            case RIGHT_EDGE_BACK_NAVIGATION:
+                if (result == BackGestureResult.BACK_COMPLETED_FROM_RIGHT) {
+                    hideHandCoachingAnimation();
+                    mFragment.changeController(
+                            TutorialStep.ENGAGED, TutorialType.LEFT_EDGE_BACK_NAVIGATION);
+                }
+                break;
+            case LEFT_EDGE_BACK_NAVIGATION:
+                if (result == BackGestureResult.BACK_COMPLETED_FROM_LEFT) {
+                    hideHandCoachingAnimation();
+                    mFragment.changeController(TutorialStep.CONFIRM);
+                }
+                break;
+        }
     }
 
     abstract Optional<Integer> getTitleStringId();
diff --git a/quickstep/src/com/android/quickstep/interaction/BackGestureTutorialFragment.java b/quickstep/src/com/android/quickstep/interaction/BackGestureTutorialFragment.java
index 54408ce..593b695 100644
--- a/quickstep/src/com/android/quickstep/interaction/BackGestureTutorialFragment.java
+++ b/quickstep/src/com/android/quickstep/interaction/BackGestureTutorialFragment.java
@@ -17,21 +17,26 @@
 
 import android.content.ActivityNotFoundException;
 import android.content.Intent;
+import android.graphics.Insets;
 import android.os.Bundle;
 import android.util.Log;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
+import android.view.WindowInsets;
 
+import androidx.annotation.NonNull;
 import androidx.fragment.app.Fragment;
 
 import com.android.launcher3.R;
+import com.android.quickstep.interaction.EdgeBackGestureHandler.BackGestureAttemptCallback;
+import com.android.quickstep.interaction.EdgeBackGestureHandler.BackGestureResult;
 
 import java.net.URISyntaxException;
 import java.util.Optional;
 
 /** Shows the Back gesture interactive tutorial. */
-public class BackGestureTutorialFragment extends Fragment {
+public class BackGestureTutorialFragment extends Fragment implements BackGestureAttemptCallback {
 
     private static final String LOG_TAG = "TutorialFragment";
     private static final String KEY_TUTORIAL_STEP = "tutorialStep";
@@ -47,6 +52,7 @@
     private Optional<BackGestureTutorialController> mTutorialController = Optional.empty();
     private View mRootView;
     private BackGestureTutorialHandAnimation mHandCoachingAnimation;
+    private EdgeBackGestureHandler mEdgeBackGestureHandler;
 
     public static BackGestureTutorialFragment newInstance(
             TutorialStep tutorialStep, TutorialType tutorialType) {
@@ -64,17 +70,25 @@
         Bundle args = savedInstanceState != null ? savedInstanceState : getArguments();
         mTutorialStep = (TutorialStep) args.getSerializable(KEY_TUTORIAL_STEP);
         mTutorialType = (TutorialType) args.getSerializable(KEY_TUTORIAL_TYPE);
+        mEdgeBackGestureHandler = new EdgeBackGestureHandler(getContext());
+        mEdgeBackGestureHandler.registerBackGestureAttemptCallback(this);
     }
 
     @Override
     public View onCreateView(
-            LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
+            @NonNull LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
         super.onCreateView(inflater, container, savedInstanceState);
 
         mRootView = inflater.inflate(R.layout.back_gesture_tutorial_fragment,
                 container, /* attachToRoot= */ false);
         mRootView.findViewById(R.id.back_gesture_tutorial_fragment_close_button)
                 .setOnClickListener(this::onCloseButtonClicked);
+        mRootView.setOnApplyWindowInsetsListener((view, insets) -> {
+            Insets systemInsets = insets.getInsets(WindowInsets.Type.systemBars());
+            mEdgeBackGestureHandler.setInsets(systemInsets.left, systemInsets.right);
+            return insets;
+        });
+        mRootView.setOnTouchListener(mEdgeBackGestureHandler);
         mHandCoachingAnimation = new BackGestureTutorialHandAnimation(getContext(), mRootView);
 
         return mRootView;
@@ -92,6 +106,14 @@
         mHandCoachingAnimation.stop();
     }
 
+    void onAttachedToWindow() {
+        mEdgeBackGestureHandler.setIsEnabled(true);
+    }
+
+    void onDetachedFromWindow() {
+        mEdgeBackGestureHandler.setIsEnabled(false);
+    }
+
     @Override
     public void onSaveInstanceState(Bundle savedInstanceState) {
         savedInstanceState.putSerializable(KEY_TUTORIAL_STEP, mTutorialStep);
@@ -125,10 +147,9 @@
         this.mTutorialType = tutorialType;
     }
 
-    void onBackPressed() {
-        if (mTutorialController.isPresent()) {
-            mTutorialController.get().onGestureDetected();
-        }
+    @Override
+    public void onBackGestureAttempted(BackGestureResult result) {
+        mTutorialController.ifPresent(controller -> controller.onGestureAttempted(result));
     }
 
     void closeTutorial() {
diff --git a/quickstep/src/com/android/quickstep/interaction/EdgeBackGestureHandler.java b/quickstep/src/com/android/quickstep/interaction/EdgeBackGestureHandler.java
new file mode 100644
index 0000000..04cd2f4
--- /dev/null
+++ b/quickstep/src/com/android/quickstep/interaction/EdgeBackGestureHandler.java
@@ -0,0 +1,274 @@
+/*
+ * Copyright (C) 2020 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.quickstep.interaction;
+
+import android.content.Context;
+import android.content.res.Resources;
+import android.graphics.PixelFormat;
+import android.graphics.Point;
+import android.graphics.PointF;
+import android.hardware.display.DisplayManager;
+import android.hardware.display.DisplayManager.DisplayListener;
+import android.os.Handler;
+import android.os.Looper;
+import android.os.SystemProperties;
+import android.view.Display;
+import android.view.MotionEvent;
+import android.view.View;
+import android.view.View.OnTouchListener;
+import android.view.ViewConfiguration;
+import android.view.WindowManager;
+import android.view.WindowManager.LayoutParams;
+
+import com.android.launcher3.ResourceUtils;
+
+/**
+ * Utility class to handle edge swipes for back gestures.
+ *
+ * Forked from platform/frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/phone/EdgeBackGestureHandler.java.
+ */
+public class EdgeBackGestureHandler implements DisplayListener, OnTouchListener {
+
+    private static final String TAG = "EdgeBackGestureHandler";
+    private static final int MAX_LONG_PRESS_TIMEOUT = SystemProperties.getInt(
+            "gestures.back_timeout", 250);
+
+    private final Context mContext;
+
+    private final Point mDisplaySize = new Point();
+    private final int mDisplayId;
+
+    // The edge width where touch down is allowed
+    private int mEdgeWidth;
+    // The bottom gesture area height
+    private int mBottomGestureHeight;
+    // The slop to distinguish between horizontal and vertical motion
+    private final float mTouchSlop;
+    // Duration after which we consider the event as longpress.
+    private final int mLongPressTimeout;
+
+    private final PointF mDownPoint = new PointF();
+    private boolean mThresholdCrossed = false;
+    private boolean mAllowGesture = false;
+    private boolean mIsEnabled;
+    private int mLeftInset;
+    private int mRightInset;
+
+    private EdgeBackGesturePanel mEdgeBackPanel;
+    private BackGestureAttemptCallback mGestureCallback;
+
+    private final EdgeBackGesturePanel.BackCallback mBackCallback =
+            new EdgeBackGesturePanel.BackCallback() {
+                @Override
+                public void triggerBack() {
+                    if (mGestureCallback != null) {
+                        mGestureCallback.onBackGestureAttempted(mEdgeBackPanel.getIsLeftPanel()
+                                ? BackGestureResult.BACK_COMPLETED_FROM_LEFT
+                                : BackGestureResult.BACK_COMPLETED_FROM_RIGHT);
+                    }
+                }
+
+                @Override
+                public void cancelBack() {
+                    if (mGestureCallback != null) {
+                        mGestureCallback.onBackGestureAttempted(mEdgeBackPanel.getIsLeftPanel()
+                                ? BackGestureResult.BACK_CANCELLED_FROM_LEFT
+                                : BackGestureResult.BACK_CANCELLED_FROM_RIGHT);
+                    }
+                }
+            };
+
+    EdgeBackGestureHandler(Context context) {
+        final Resources res = context.getResources();
+        mContext = context;
+        mDisplayId = context.getDisplay() == null
+                ? Display.DEFAULT_DISPLAY : context.getDisplay().getDisplayId();
+
+        mTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop();
+        mLongPressTimeout = Math.min(MAX_LONG_PRESS_TIMEOUT,
+                ViewConfiguration.getLongPressTimeout());
+
+        mBottomGestureHeight =
+            ResourceUtils.getNavbarSize(ResourceUtils.NAVBAR_BOTTOM_GESTURE_SIZE, res);
+        mEdgeWidth = ResourceUtils.getNavbarSize("config_backGestureInset", res);
+    }
+
+    void setIsEnabled(boolean isEnabled) {
+        if (isEnabled == mIsEnabled) {
+            return;
+        }
+        mIsEnabled = isEnabled;
+
+        if (mEdgeBackPanel != null) {
+            mEdgeBackPanel.onDestroy();
+            mEdgeBackPanel = null;
+        }
+
+        if (!mIsEnabled) {
+            mContext.getSystemService(DisplayManager.class).unregisterDisplayListener(this);
+        } else {
+            updateDisplaySize();
+            mContext.getSystemService(DisplayManager.class).registerDisplayListener(this,
+                    new Handler(Looper.getMainLooper()));
+
+            // Add a nav bar panel window.
+            mEdgeBackPanel = new EdgeBackGesturePanel(mContext);
+            mEdgeBackPanel.setBackCallback(mBackCallback);
+            mEdgeBackPanel.setLayoutParams(createLayoutParams());
+            updateDisplaySize();
+        }
+    }
+
+    void registerBackGestureAttemptCallback(BackGestureAttemptCallback callback) {
+        mGestureCallback = callback;
+    }
+
+    private WindowManager.LayoutParams createLayoutParams() {
+        Resources resources = mContext.getResources();
+        WindowManager.LayoutParams layoutParams = new WindowManager.LayoutParams(
+                ResourceUtils.getNavbarSize("navigation_edge_panel_width", resources),
+                ResourceUtils.getNavbarSize("navigation_edge_panel_height", resources),
+                LayoutParams.TYPE_APPLICATION_PANEL,
+                WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
+                        | WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL
+                        | WindowManager.LayoutParams.FLAG_SPLIT_TOUCH
+                        | WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN,
+                PixelFormat.TRANSLUCENT);
+        layoutParams.setTitle(TAG + mDisplayId);
+        layoutParams.windowAnimations = 0;
+        layoutParams.setFitInsetsTypes(0 /* types */);
+        return layoutParams;
+    }
+
+    @Override
+    public boolean onTouch(View view, MotionEvent motionEvent) {
+        if (mIsEnabled) {
+            onMotionEvent(motionEvent);
+            return true;
+        }
+        return false;
+    }
+
+    private boolean isWithinTouchRegion(int x, int y) {
+        // Disallow if too far from the edge
+        if (x > mEdgeWidth + mLeftInset && x < (mDisplaySize.x - mEdgeWidth - mRightInset)) {
+            return false;
+        }
+
+        // Disallow if we are in the bottom gesture area
+        if (y >= (mDisplaySize.y - mBottomGestureHeight)) {
+            return false;
+        }
+
+        return true;
+    }
+
+    private void cancelGesture(MotionEvent ev) {
+        // Send action cancel to reset all the touch events
+        mAllowGesture = false;
+        MotionEvent cancelEv = MotionEvent.obtain(ev);
+        cancelEv.setAction(MotionEvent.ACTION_CANCEL);
+        mEdgeBackPanel.onMotionEvent(cancelEv);
+        cancelEv.recycle();
+    }
+
+    private void onMotionEvent(MotionEvent ev) {
+        int action = ev.getActionMasked();
+        if (action == MotionEvent.ACTION_DOWN) {
+            boolean isOnLeftEdge = ev.getX() <= mEdgeWidth + mLeftInset;
+            mAllowGesture = isWithinTouchRegion((int) ev.getX(), (int) ev.getY());
+            if (mAllowGesture) {
+                mEdgeBackPanel.setIsLeftPanel(isOnLeftEdge);
+                mEdgeBackPanel.onMotionEvent(ev);
+
+                mDownPoint.set(ev.getX(), ev.getY());
+                mThresholdCrossed = false;
+            }
+        } else if (mAllowGesture) {
+            if (!mThresholdCrossed) {
+                if (action == MotionEvent.ACTION_POINTER_DOWN) {
+                    // We do not support multi touch for back gesture
+                    cancelGesture(ev);
+                    return;
+                } else if (action == MotionEvent.ACTION_MOVE) {
+                    if ((ev.getEventTime() - ev.getDownTime()) > mLongPressTimeout) {
+                        cancelGesture(ev);
+                        return;
+                    }
+                    float dx = Math.abs(ev.getX() - mDownPoint.x);
+                    float dy = Math.abs(ev.getY() - mDownPoint.y);
+                    if (dy > dx && dy > mTouchSlop) {
+                        cancelGesture(ev);
+                        return;
+
+                    } else if (dx > dy && dx > mTouchSlop) {
+                        mThresholdCrossed = true;
+                    }
+                }
+
+            }
+
+            // forward touch
+            mEdgeBackPanel.onMotionEvent(ev);
+        }
+
+        if (action == MotionEvent.ACTION_UP || action == MotionEvent.ACTION_CANCEL) {
+            if (!mAllowGesture && mGestureCallback != null) {
+                mGestureCallback.onBackGestureAttempted(BackGestureResult.BACK_NOT_STARTED);
+            }
+        }
+    }
+
+    @Override
+    public void onDisplayAdded(int displayId) { }
+
+    @Override
+    public void onDisplayRemoved(int displayId) { }
+
+    @Override
+    public void onDisplayChanged(int displayId) {
+        if (displayId == mDisplayId) {
+            updateDisplaySize();
+        }
+    }
+
+    private void updateDisplaySize() {
+        mContext.getDisplay().getRealSize(mDisplaySize);
+        if (mEdgeBackPanel != null) {
+            mEdgeBackPanel.setDisplaySize(mDisplaySize);
+        }
+    }
+
+    void setInsets(int leftInset, int rightInset) {
+        mLeftInset = leftInset;
+        mRightInset = rightInset;
+    }
+
+    enum BackGestureResult {
+        UNKNOWN,
+        BACK_COMPLETED_FROM_LEFT,
+        BACK_COMPLETED_FROM_RIGHT,
+        BACK_CANCELLED_FROM_LEFT,
+        BACK_CANCELLED_FROM_RIGHT,
+        BACK_NOT_STARTED,
+    }
+
+    /** Callback to let the UI react to attempted back gestures. */
+    interface BackGestureAttemptCallback {
+        /** Called whenever any touch is completed. */
+        void onBackGestureAttempted(BackGestureResult result);
+    }
+}
diff --git a/quickstep/src/com/android/quickstep/interaction/EdgeBackGesturePanel.java b/quickstep/src/com/android/quickstep/interaction/EdgeBackGesturePanel.java
new file mode 100644
index 0000000..34eeafc
--- /dev/null
+++ b/quickstep/src/com/android/quickstep/interaction/EdgeBackGesturePanel.java
@@ -0,0 +1,701 @@
+/*
+ * Copyright (C) 2019 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.quickstep.interaction;
+
+import android.animation.ValueAnimator;
+import android.annotation.SuppressLint;
+import android.content.Context;
+import android.content.res.Configuration;
+import android.content.res.Resources;
+import android.graphics.Canvas;
+import android.graphics.Paint;
+import android.graphics.Path;
+import android.graphics.Point;
+import android.os.SystemClock;
+import android.view.Gravity;
+import android.view.MotionEvent;
+import android.view.VelocityTracker;
+import android.view.View;
+import android.view.WindowManager;
+import android.view.animation.Interpolator;
+import android.view.animation.PathInterpolator;
+
+import androidx.core.math.MathUtils;
+import androidx.dynamicanimation.animation.DynamicAnimation;
+import androidx.dynamicanimation.animation.FloatPropertyCompat;
+import androidx.dynamicanimation.animation.SpringAnimation;
+import androidx.dynamicanimation.animation.SpringForce;
+
+import com.android.launcher3.R;
+import com.android.launcher3.ResourceUtils;
+import com.android.launcher3.anim.Interpolators;
+import com.android.launcher3.util.VibratorWrapper;
+
+/** Forked from platform/frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/phone/NavigationBarEdgePanel.java. */
+public class EdgeBackGesturePanel extends View {
+
+    private static final String LOG_TAG = "EdgeBackGesturePanel";
+
+    private static final long DISAPPEAR_FADE_ANIMATION_DURATION_MS = 80;
+    private static final long DISAPPEAR_ARROW_ANIMATION_DURATION_MS = 100;
+
+    /**
+     * The time required since the first vibration effect to automatically trigger a click
+     */
+    private static final int GESTURE_DURATION_FOR_CLICK_MS = 400;
+
+    /**
+     * The basic translation in dp where the arrow resides
+     */
+    private static final int BASE_TRANSLATION_DP = 32;
+
+    /**
+     * The length of the arrow leg measured from the center to the end
+     */
+    private static final int ARROW_LENGTH_DP = 18;
+
+    /**
+     * The angle measured from the xAxis, where the leg is when the arrow rests
+     */
+    private static final int ARROW_ANGLE_WHEN_EXTENDED_DEGREES = 56;
+
+    /**
+     * The angle that is added per 1000 px speed to the angle of the leg
+     */
+    private static final int ARROW_ANGLE_ADDED_PER_1000_SPEED = 4;
+
+    /**
+     * The maximum angle offset allowed due to speed
+     */
+    private static final int ARROW_MAX_ANGLE_SPEED_OFFSET_DEGREES = 4;
+
+    /**
+     * The thickness of the arrow. Adjusted to match the home handle (approximately)
+     */
+    private static final float ARROW_THICKNESS_DP = 2.5f;
+
+    /**
+     * The amount of rubber banding we do for the vertical translation
+     */
+    private static final int RUBBER_BAND_AMOUNT = 15;
+
+    /**
+     * The interpolator used to rubberband
+     */
+    private static final Interpolator RUBBER_BAND_INTERPOLATOR =
+            new PathInterpolator(1.0f / 5.0f, 1.0f, 1.0f, 1.0f);
+
+    /**
+     * The amount of rubber banding we do for the translation before base translation
+     */
+    private static final int RUBBER_BAND_AMOUNT_APPEAR = 4;
+
+    /**
+     * The interpolator used to rubberband the appearing of the arrow.
+     */
+    private static final Interpolator RUBBER_BAND_INTERPOLATOR_APPEAR =
+            new PathInterpolator(1.0f / RUBBER_BAND_AMOUNT_APPEAR, 1.0f, 1.0f, 1.0f);
+
+    private final WindowManager mWindowManager;
+    private BackCallback mBackCallback;
+
+    /**
+     * The paint the arrow is drawn with
+     */
+    private final Paint mPaint = new Paint();
+
+    private final float mDensity;
+    private final float mBaseTranslation;
+    private final float mArrowLength;
+    private final float mArrowThickness;
+
+    /**
+     * The minimum delta needed in movement for the arrow to change direction / stop triggering back
+     */
+    private final float mMinDeltaForSwitch;
+    // The closest to y = 0 that the arrow will be displayed.
+    private int mMinArrowPosition;
+    // The amount the arrow is shifted to avoid the finger.
+    private int mFingerOffset;
+
+    private final float mSwipeThreshold;
+    private final Path mArrowPath = new Path();
+    private final Point mDisplaySize = new Point();
+
+    private final SpringAnimation mAngleAnimation;
+    private final SpringAnimation mTranslationAnimation;
+    private final SpringAnimation mVerticalTranslationAnimation;
+    private final SpringForce mAngleAppearForce;
+    private final SpringForce mAngleDisappearForce;
+    private final ValueAnimator mArrowDisappearAnimation;
+    private final SpringForce mRegularTranslationSpring;
+    private final SpringForce mTriggerBackSpring;
+
+    private VelocityTracker mVelocityTracker;
+    private int mArrowPaddingEnd;
+    private WindowManager.LayoutParams mLayoutParams;
+
+    /**
+     * True if the panel is currently on the left of the screen
+     */
+    private boolean mIsLeftPanel;
+
+    private float mStartX;
+    private float mStartY;
+    private float mCurrentAngle;
+    /**
+     * The current translation of the arrow
+     */
+    private float mCurrentTranslation;
+    /**
+     * Where the arrow will be in the resting position.
+     */
+    private float mDesiredTranslation;
+
+    private boolean mDragSlopPassed;
+    private boolean mArrowsPointLeft;
+    private float mMaxTranslation;
+    private boolean mTriggerBack;
+    private float mPreviousTouchTranslation;
+    private float mTotalTouchDelta;
+    private float mVerticalTranslation;
+    private float mDesiredVerticalTranslation;
+    private float mDesiredAngle;
+    private float mAngleOffset;
+    private float mDisappearAmount;
+    private long mVibrationTime;
+    private int mScreenSize;
+
+    private final DynamicAnimation.OnAnimationEndListener mSetGoneEndListener =
+            new DynamicAnimation.OnAnimationEndListener() {
+                @Override
+                public void onAnimationEnd(
+                        DynamicAnimation animation, boolean canceled, float value, float velocity) {
+                    animation.removeEndListener(this);
+                    if (!canceled) {
+                        setVisibility(GONE);
+                    }
+                }
+            };
+
+    private static final FloatPropertyCompat<EdgeBackGesturePanel> CURRENT_ANGLE =
+            new FloatPropertyCompat<EdgeBackGesturePanel>("currentAngle") {
+                @Override
+                public void setValue(EdgeBackGesturePanel object, float value) {
+                    object.setCurrentAngle(value);
+                }
+
+                @Override
+                public float getValue(EdgeBackGesturePanel object) {
+                    return object.getCurrentAngle();
+                }
+            };
+
+    private static final FloatPropertyCompat<EdgeBackGesturePanel> CURRENT_TRANSLATION =
+            new FloatPropertyCompat<EdgeBackGesturePanel>("currentTranslation") {
+                @Override
+                public void setValue(EdgeBackGesturePanel object, float value) {
+                    object.setCurrentTranslation(value);
+                }
+
+                @Override
+                public float getValue(EdgeBackGesturePanel object) {
+                    return object.getCurrentTranslation();
+                }
+            };
+
+    private static final FloatPropertyCompat<EdgeBackGesturePanel> CURRENT_VERTICAL_TRANSLATION =
+            new FloatPropertyCompat<EdgeBackGesturePanel>("verticalTranslation") {
+
+                @Override
+                public void setValue(EdgeBackGesturePanel object, float value) {
+                    object.setVerticalTranslation(value);
+                }
+
+                @Override
+                public float getValue(EdgeBackGesturePanel object) {
+                    return object.getVerticalTranslation();
+                }
+            };
+
+    public EdgeBackGesturePanel(Context context) {
+        super(context);
+
+        mWindowManager = context.getSystemService(WindowManager.class);
+
+        mDensity = context.getResources().getDisplayMetrics().density;
+
+        mBaseTranslation = dp(BASE_TRANSLATION_DP);
+        mArrowLength = dp(ARROW_LENGTH_DP);
+        mArrowThickness = dp(ARROW_THICKNESS_DP);
+        mMinDeltaForSwitch = dp(32);
+
+        mPaint.setStrokeWidth(mArrowThickness);
+        mPaint.setStrokeCap(Paint.Cap.ROUND);
+        mPaint.setAntiAlias(true);
+        mPaint.setStyle(Paint.Style.STROKE);
+        mPaint.setStrokeJoin(Paint.Join.ROUND);
+
+        mArrowDisappearAnimation = ValueAnimator.ofFloat(0.0f, 1.0f);
+        mArrowDisappearAnimation.setDuration(DISAPPEAR_ARROW_ANIMATION_DURATION_MS);
+        mArrowDisappearAnimation.setInterpolator(Interpolators.FAST_OUT_SLOW_IN);
+        mArrowDisappearAnimation.addUpdateListener(animation -> {
+            mDisappearAmount = (float) animation.getAnimatedValue();
+            invalidate();
+        });
+
+        mAngleAnimation =
+                new SpringAnimation(this, CURRENT_ANGLE);
+        mAngleAppearForce = new SpringForce()
+                .setStiffness(500)
+                .setDampingRatio(0.5f);
+        mAngleDisappearForce = new SpringForce()
+                .setStiffness(SpringForce.STIFFNESS_MEDIUM)
+                .setDampingRatio(SpringForce.DAMPING_RATIO_MEDIUM_BOUNCY)
+                .setFinalPosition(90);
+        mAngleAnimation.setSpring(mAngleAppearForce).setMaxValue(90);
+
+        mTranslationAnimation =
+                new SpringAnimation(this, CURRENT_TRANSLATION);
+        mRegularTranslationSpring = new SpringForce()
+                .setStiffness(SpringForce.STIFFNESS_MEDIUM)
+                .setDampingRatio(SpringForce.DAMPING_RATIO_LOW_BOUNCY);
+        mTriggerBackSpring = new SpringForce()
+                .setStiffness(450)
+                .setDampingRatio(SpringForce.DAMPING_RATIO_LOW_BOUNCY);
+        mTranslationAnimation.setSpring(mRegularTranslationSpring);
+        mVerticalTranslationAnimation =
+                new SpringAnimation(this, CURRENT_VERTICAL_TRANSLATION);
+        mVerticalTranslationAnimation.setSpring(
+                new SpringForce()
+                        .setStiffness(SpringForce.STIFFNESS_MEDIUM)
+                        .setDampingRatio(SpringForce.DAMPING_RATIO_LOW_BOUNCY));
+        mPaint.setColor(context.getColor(R.color.back_arrow_color_dark));
+        loadDimens();
+        updateArrowDirection();
+
+        mSwipeThreshold = ResourceUtils.getDimenByName(
+            "navigation_edge_action_drag_threshold", context.getResources(), 16 /* defaultValue */);
+        setVisibility(GONE);
+    }
+
+    void onDestroy() {
+        mWindowManager.removeView(this);
+    }
+
+    @Override
+    public boolean hasOverlappingRendering() {
+        return false;
+    }
+
+    @SuppressLint("RtlHardcoded")
+    void setIsLeftPanel(boolean isLeftPanel) {
+        mIsLeftPanel = isLeftPanel;
+        mLayoutParams.gravity = mIsLeftPanel
+                ? (Gravity.LEFT | Gravity.TOP)
+                : (Gravity.RIGHT | Gravity.TOP);
+    }
+
+    boolean getIsLeftPanel() {
+        return mIsLeftPanel;
+    }
+
+    void setDisplaySize(Point displaySize) {
+        mDisplaySize.set(displaySize.x, displaySize.y);
+        mScreenSize = Math.min(mDisplaySize.x, mDisplaySize.y);
+    }
+
+    void setBackCallback(BackCallback callback) {
+        mBackCallback = callback;
+    }
+
+    void setLayoutParams(WindowManager.LayoutParams layoutParams) {
+        mLayoutParams = layoutParams;
+        mWindowManager.addView(this, mLayoutParams);
+    }
+
+    private float getCurrentAngle() {
+        return mCurrentAngle;
+    }
+
+    private float getCurrentTranslation() {
+        return mCurrentTranslation;
+    }
+
+    void onMotionEvent(MotionEvent event) {
+        if (mVelocityTracker == null) {
+            mVelocityTracker = VelocityTracker.obtain();
+        }
+        mVelocityTracker.addMovement(event);
+        switch (event.getActionMasked()) {
+            case MotionEvent.ACTION_DOWN:
+                mDragSlopPassed = false;
+                resetOnDown();
+                mStartX = event.getX();
+                mStartY = event.getY();
+                setVisibility(VISIBLE);
+                updatePosition(event.getY());
+                mWindowManager.updateViewLayout(this, mLayoutParams);
+                break;
+            case MotionEvent.ACTION_MOVE:
+                handleMoveEvent(event);
+                break;
+            case MotionEvent.ACTION_UP:
+                if (mTriggerBack) {
+                    triggerBack();
+                } else {
+                    cancelBack();
+                }
+                mVelocityTracker.recycle();
+                mVelocityTracker = null;
+                break;
+            case MotionEvent.ACTION_CANCEL:
+                cancelBack();
+                mVelocityTracker.recycle();
+                mVelocityTracker = null;
+                break;
+        }
+    }
+
+    @Override
+    protected void onConfigurationChanged(Configuration newConfig) {
+        super.onConfigurationChanged(newConfig);
+        updateArrowDirection();
+        loadDimens();
+    }
+
+    @Override
+    protected void onDraw(Canvas canvas) {
+        float pointerPosition = mCurrentTranslation - mArrowThickness / 2.0f;
+        canvas.save();
+        canvas.translate(
+                mIsLeftPanel ? pointerPosition : getWidth() - pointerPosition,
+                (getHeight() * 0.5f) + mVerticalTranslation);
+
+        // Let's calculate the position of the end based on the angle
+        float x = (polarToCartX(mCurrentAngle) * mArrowLength);
+        float y = (polarToCartY(mCurrentAngle) * mArrowLength);
+        Path arrowPath = calculatePath(x, y);
+
+        canvas.drawPath(arrowPath, mPaint);
+        canvas.restore();
+    }
+
+    @Override
+    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
+        super.onLayout(changed, left, top, right, bottom);
+        mMaxTranslation = getWidth() - mArrowPaddingEnd;
+    }
+
+    private void loadDimens() {
+        Resources res = getResources();
+        mArrowPaddingEnd = ResourceUtils.getDimenByName("navigation_edge_panel_padding", res, 8);
+        mMinArrowPosition = ResourceUtils.getDimenByName("navigation_edge_arrow_min_y", res, 64);
+        mFingerOffset = ResourceUtils.getDimenByName("navigation_edge_finger_offset", res, 48);
+    }
+
+    private void updateArrowDirection() {
+        // Both panels arrow point the same way
+        mArrowsPointLeft = getLayoutDirection() == LAYOUT_DIRECTION_LTR;
+        invalidate();
+    }
+
+    private float getStaticArrowWidth() {
+        return polarToCartX(ARROW_ANGLE_WHEN_EXTENDED_DEGREES) * mArrowLength;
+    }
+
+    private float polarToCartX(float angleInDegrees) {
+        return (float) Math.cos(Math.toRadians(angleInDegrees));
+    }
+
+    private float polarToCartY(float angleInDegrees) {
+        return (float) Math.sin(Math.toRadians(angleInDegrees));
+    }
+
+    private Path calculatePath(float x, float y) {
+        if (!mArrowsPointLeft) {
+            x = -x;
+        }
+        float extent = lerp(1.0f, 0.75f, mDisappearAmount);
+        x = x * extent;
+        y = y * extent;
+        mArrowPath.reset();
+        mArrowPath.moveTo(x, y);
+        mArrowPath.lineTo(0, 0);
+        mArrowPath.lineTo(x, -y);
+        return mArrowPath;
+    }
+
+    private static float lerp(float start, float stop, float amount) {
+        return start + (stop - start) * amount;
+    }
+
+    private void triggerBack() {
+        if (mBackCallback != null) {
+            mBackCallback.triggerBack();
+        }
+
+        if (mVelocityTracker == null) {
+            mVelocityTracker = VelocityTracker.obtain();
+        }
+        mVelocityTracker.computeCurrentVelocity(1000);
+        // Only do the extra translation if we're not already flinging
+        boolean isSlow = Math.abs(mVelocityTracker.getXVelocity()) < 500;
+        if (isSlow
+                || SystemClock.uptimeMillis() - mVibrationTime >= GESTURE_DURATION_FOR_CLICK_MS) {
+            VibratorWrapper.INSTANCE.get(getContext()).vibrate(VibratorWrapper.EFFECT_CLICK);
+        }
+
+        // Let's also snap the angle a bit
+        if (mAngleOffset > -4) {
+            mAngleOffset = Math.max(-8, mAngleOffset - 8);
+            updateAngle(true /* animated */);
+        }
+
+        // Finally, after the translation, animate back and disappear the arrow
+        Runnable translationEnd = () -> {
+            // let's snap it back
+            mAngleOffset = Math.max(0, mAngleOffset + 8);
+            updateAngle(true /* animated */);
+
+            mTranslationAnimation.setSpring(mTriggerBackSpring);
+            // Translate the arrow back a bit to make for a nice transition
+            setDesiredTranslation(mDesiredTranslation - dp(32), true /* animated */);
+            animate().alpha(0f).setDuration(DISAPPEAR_FADE_ANIMATION_DURATION_MS)
+                    .withEndAction(() -> setVisibility(GONE));
+            mArrowDisappearAnimation.start();
+        };
+        if (mTranslationAnimation.isRunning()) {
+            mTranslationAnimation.addEndListener(new DynamicAnimation.OnAnimationEndListener() {
+                @Override
+                public void onAnimationEnd(DynamicAnimation animation, boolean canceled,
+                        float value,
+                        float velocity) {
+                    animation.removeEndListener(this);
+                    if (!canceled) {
+                        translationEnd.run();
+                    }
+                }
+            });
+        } else {
+            translationEnd.run();
+        }
+    }
+
+    private void cancelBack() {
+        if (mBackCallback != null) {
+            mBackCallback.cancelBack();
+        }
+
+        if (mTranslationAnimation.isRunning()) {
+            mTranslationAnimation.addEndListener(mSetGoneEndListener);
+        } else {
+            setVisibility(GONE);
+        }
+    }
+
+    private void resetOnDown() {
+        animate().cancel();
+        mAngleAnimation.cancel();
+        mTranslationAnimation.cancel();
+        mVerticalTranslationAnimation.cancel();
+        mArrowDisappearAnimation.cancel();
+        mAngleOffset = 0;
+        mTranslationAnimation.setSpring(mRegularTranslationSpring);
+        // Reset the arrow to the side
+        setTriggerBack(false /* triggerBack */, false /* animated */);
+        setDesiredTranslation(0, false /* animated */);
+        setCurrentTranslation(0);
+        updateAngle(false /* animate */);
+        mPreviousTouchTranslation = 0;
+        mTotalTouchDelta = 0;
+        mVibrationTime = 0;
+        setDesiredVerticalTransition(0, false /* animated */);
+    }
+
+    private void handleMoveEvent(MotionEvent event) {
+        float x = event.getX();
+        float y = event.getY();
+        float touchTranslation = Math.abs(x - mStartX);
+        float yOffset = y - mStartY;
+        float delta = touchTranslation - mPreviousTouchTranslation;
+        if (Math.abs(delta) > 0) {
+            if (Math.signum(delta) == Math.signum(mTotalTouchDelta)) {
+                mTotalTouchDelta += delta;
+            } else {
+                mTotalTouchDelta = delta;
+            }
+        }
+        mPreviousTouchTranslation = touchTranslation;
+
+        // Apply a haptic on drag slop passed
+        if (!mDragSlopPassed && touchTranslation > mSwipeThreshold) {
+            mDragSlopPassed = true;
+            VibratorWrapper.INSTANCE.get(getContext()).vibrate(VibratorWrapper.EFFECT_CLICK);
+            mVibrationTime = SystemClock.uptimeMillis();
+
+            // Let's show the arrow and animate it in!
+            mDisappearAmount = 0.0f;
+            setAlpha(1f);
+            // And animate it go to back by default!
+            setTriggerBack(true /* triggerBack */, true /* animated */);
+        }
+
+        // Let's make sure we only go to the baseextend and apply rubberbanding afterwards
+        if (touchTranslation > mBaseTranslation) {
+            float diff = touchTranslation - mBaseTranslation;
+            float progress = MathUtils.clamp(diff / (mScreenSize - mBaseTranslation), 0, 1);
+            progress = RUBBER_BAND_INTERPOLATOR.getInterpolation(progress)
+                    * (mMaxTranslation - mBaseTranslation);
+            touchTranslation = mBaseTranslation + progress;
+        } else {
+            float diff = mBaseTranslation - touchTranslation;
+            float progress = MathUtils.clamp(diff / mBaseTranslation, 0, 1);
+            progress = RUBBER_BAND_INTERPOLATOR_APPEAR.getInterpolation(progress)
+                    * (mBaseTranslation / RUBBER_BAND_AMOUNT_APPEAR);
+            touchTranslation = mBaseTranslation - progress;
+        }
+        // By default we just assume the current direction is kept
+        boolean triggerBack = mTriggerBack;
+
+        //  First lets see if we had continuous motion in one direction for a while
+        if (Math.abs(mTotalTouchDelta) > mMinDeltaForSwitch) {
+            triggerBack = mTotalTouchDelta > 0;
+        }
+
+        // Then, let's see if our velocity tells us to change direction
+        mVelocityTracker.computeCurrentVelocity(1000);
+        float xVelocity = mVelocityTracker.getXVelocity();
+        float yVelocity = mVelocityTracker.getYVelocity();
+        float velocity = (float) Math.hypot(xVelocity, yVelocity);
+        mAngleOffset = Math.min(velocity / 1000 * ARROW_ANGLE_ADDED_PER_1000_SPEED,
+                ARROW_MAX_ANGLE_SPEED_OFFSET_DEGREES) * Math.signum(xVelocity);
+        if (mIsLeftPanel && mArrowsPointLeft || !mIsLeftPanel && !mArrowsPointLeft) {
+            mAngleOffset *= -1;
+        }
+
+        // Last if the direction in Y is bigger than X * 2 we also abort
+        if (Math.abs(yOffset) > Math.abs(x - mStartX) * 2) {
+            triggerBack = false;
+        }
+        setTriggerBack(triggerBack, true /* animated */);
+
+        if (!mTriggerBack) {
+            touchTranslation = 0;
+        } else if (mIsLeftPanel && mArrowsPointLeft
+                || (!mIsLeftPanel && !mArrowsPointLeft)) {
+            // If we're on the left we should move less, because the arrow is facing the other
+            // direction
+            touchTranslation -= getStaticArrowWidth();
+        }
+        setDesiredTranslation(touchTranslation, true /* animated */);
+        updateAngle(true /* animated */);
+
+        float maxYOffset = getHeight() / 2.0f - mArrowLength;
+        float progress =
+                MathUtils.clamp(Math.abs(yOffset) / (maxYOffset * RUBBER_BAND_AMOUNT), 0, 1);
+        float verticalTranslation = RUBBER_BAND_INTERPOLATOR.getInterpolation(progress)
+                * maxYOffset * Math.signum(yOffset);
+        setDesiredVerticalTransition(verticalTranslation, true /* animated */);
+    }
+
+    private void updatePosition(float touchY) {
+        float position = touchY - mFingerOffset;
+        position = Math.max(position, mMinArrowPosition);
+        position -= mLayoutParams.height / 2.0f;
+        mLayoutParams.y = MathUtils.clamp((int) position, 0, mDisplaySize.y);
+    }
+
+    private void setDesiredVerticalTransition(float verticalTranslation, boolean animated) {
+        if (mDesiredVerticalTranslation != verticalTranslation) {
+            mDesiredVerticalTranslation = verticalTranslation;
+            if (!animated) {
+                setVerticalTranslation(verticalTranslation);
+            } else {
+                mVerticalTranslationAnimation.animateToFinalPosition(verticalTranslation);
+            }
+            invalidate();
+        }
+    }
+
+    private void setVerticalTranslation(float verticalTranslation) {
+        mVerticalTranslation = verticalTranslation;
+        invalidate();
+    }
+
+    private float getVerticalTranslation() {
+        return mVerticalTranslation;
+    }
+
+    private void setDesiredTranslation(float desiredTranslation, boolean animated) {
+        if (mDesiredTranslation != desiredTranslation) {
+            mDesiredTranslation = desiredTranslation;
+            if (!animated) {
+                setCurrentTranslation(desiredTranslation);
+            } else {
+                mTranslationAnimation.animateToFinalPosition(desiredTranslation);
+            }
+        }
+    }
+
+    private void setCurrentTranslation(float currentTranslation) {
+        mCurrentTranslation = currentTranslation;
+        invalidate();
+    }
+
+    private void setTriggerBack(boolean triggerBack, boolean animated) {
+        if (mTriggerBack != triggerBack) {
+            mTriggerBack = triggerBack;
+            mAngleAnimation.cancel();
+            updateAngle(animated);
+            // Whenever the trigger back state changes the existing translation animation should be
+            // cancelled
+            mTranslationAnimation.cancel();
+        }
+    }
+
+    private void updateAngle(boolean animated) {
+        float newAngle = mTriggerBack ? ARROW_ANGLE_WHEN_EXTENDED_DEGREES + mAngleOffset : 90;
+        if (newAngle != mDesiredAngle) {
+            if (!animated) {
+                setCurrentAngle(newAngle);
+            } else {
+                mAngleAnimation.setSpring(mTriggerBack ? mAngleAppearForce : mAngleDisappearForce);
+                mAngleAnimation.animateToFinalPosition(newAngle);
+            }
+            mDesiredAngle = newAngle;
+        }
+    }
+
+    private void setCurrentAngle(float currentAngle) {
+        mCurrentAngle = currentAngle;
+        invalidate();
+    }
+
+    private float dp(float dp) {
+        return mDensity * dp;
+    }
+
+    /** Callback to let the gesture handler react to the detected back gestures. */
+    interface BackCallback {
+        /** Indicates that a Back gesture was recognized. */
+        void triggerBack();
+
+        /** Indicates that the gesture was cancelled. */
+        void cancelBack();
+    }
+}
diff --git a/quickstep/src/com/android/quickstep/interaction/GestureSandboxActivity.java b/quickstep/src/com/android/quickstep/interaction/GestureSandboxActivity.java
index 8081ad7..4815366 100644
--- a/quickstep/src/com/android/quickstep/interaction/GestureSandboxActivity.java
+++ b/quickstep/src/com/android/quickstep/interaction/GestureSandboxActivity.java
@@ -30,12 +30,11 @@
 import com.android.quickstep.interaction.BackGestureTutorialFragment.TutorialType;
 
 import java.util.List;
-import java.util.Optional;
 
 /** Shows the gesture interactive sandbox in full screen mode. */
 public class GestureSandboxActivity extends FragmentActivity {
 
-    Optional<BackGestureTutorialFragment> mFragment = Optional.empty();
+    private BackGestureTutorialFragment mFragment;
 
     @Override
     protected void onCreate(Bundle savedInstanceState) {
@@ -43,10 +42,10 @@
         requestWindowFeature(Window.FEATURE_NO_TITLE);
         setContentView(R.layout.back_gesture_tutorial_activity);
 
-        mFragment = Optional.of(BackGestureTutorialFragment.newInstance(TutorialStep.ENGAGED,
-                TutorialType.RIGHT_EDGE_BACK_NAVIGATION));
+        mFragment = BackGestureTutorialFragment.newInstance(
+            TutorialStep.ENGAGED, TutorialType.RIGHT_EDGE_BACK_NAVIGATION);
         getSupportFragmentManager().beginTransaction()
-                .add(R.id.back_gesture_tutorial_fragment_container, mFragment.get())
+                .add(R.id.back_gesture_tutorial_fragment_container, mFragment)
                 .commit();
     }
 
@@ -54,6 +53,13 @@
     public void onAttachedToWindow() {
         super.onAttachedToWindow();
         disableSystemGestures();
+        mFragment.onAttachedToWindow();
+    }
+
+    @Override
+    public void onDetachedFromWindow() {
+        super.onDetachedFromWindow();
+        mFragment.onDetachedFromWindow();
     }
 
     @Override
@@ -64,13 +70,6 @@
         }
     }
 
-    @Override
-    public void onBackPressed() {
-        if (mFragment.isPresent()) {
-            mFragment.get().onBackPressed();
-        }
-    }
-
     private void hideSystemUI() {
         getWindow().getDecorView().setSystemUiVisibility(
                 View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY
diff --git a/src/com/android/launcher3/util/VibratorWrapper.java b/src/com/android/launcher3/util/VibratorWrapper.java
index 04741a1..b0defd4 100644
--- a/src/com/android/launcher3/util/VibratorWrapper.java
+++ b/src/com/android/launcher3/util/VibratorWrapper.java
@@ -39,7 +39,7 @@
     public static final MainThreadInitializedObject<VibratorWrapper> INSTANCE =
             new MainThreadInitializedObject<>(VibratorWrapper::new);
 
-    private static final VibrationEffect EFFECT_CLICK =
+    public static final VibrationEffect EFFECT_CLICK =
             createPredefined(VibrationEffect.EFFECT_CLICK);
 
     /**