Predictive back: widget to all apps

This CL adds a layer of OnBackPressedHanlderRouter to Launcher:
1. 4 OnBackPressedHandler(s) are added in such order: auto cancel action mode handler, drag handler, view handler and state handler
2. first handler who can handle back will handle the entire back gesture
3. Let WidgetsFullSheet to handle widget to all apps transition

Bug: b/260956481
Test: manual
Change-Id: Idbce3dcec746226dd68aaabaddc8fe01334e9673

quickstep/src/com/android/launcher3/taskbar/TaskbarDragLayer.java

@@ -194,7 +194,8 @@ public class TaskbarDragLayer extends BaseDragLayer<TaskbarActivityContext> {
     public boolean dispatchKeyEvent(KeyEvent event) {
         if (event.getAction() == ACTION_UP && event.getKeyCode() == KEYCODE_BACK) {
             AbstractFloatingView topView = AbstractFloatingView.getTopOpenView(mActivity);
-            if (topView != null && topView.onBackPressed()) {
+            if (topView != null && topView.canHandleBack()) {
+                topView.onBackInvoked();
                 // Handled by the floating view.
                 return true;
             }

quickstep/src/com/android/launcher3/taskbar/overlay/TaskbarOverlayDragLayer.java

@@ -71,7 +71,8 @@ public class TaskbarOverlayDragLayer extends
     public boolean dispatchKeyEvent(KeyEvent event) {
         if (event.getAction() == ACTION_UP && event.getKeyCode() == KEYCODE_BACK) {
             AbstractFloatingView topView = AbstractFloatingView.getTopOpenView(mActivity);
-            if (topView != null && topView.onBackPressed()) {
+            if (topView != null && topView.canHandleBack()) {
+                topView.onBackInvoked();
                 return true;
             }
         }

quickstep/src/com/android/launcher3/uioverrides/QuickstepLauncher.java

@@ -84,6 +84,7 @@ import com.android.launcher3.DeviceProfile;
 import com.android.launcher3.Launcher;
 import com.android.launcher3.LauncherSettings.Favorites;
 import com.android.launcher3.LauncherState;
+import com.android.launcher3.OnBackPressedHandler;
 import com.android.launcher3.QuickstepAccessibilityDelegate;
 import com.android.launcher3.QuickstepTransitionManager;
 import com.android.launcher3.R;
@@ -638,20 +639,49 @@ public class QuickstepLauncher extends Launcher {
         getOnBackInvokedDispatcher().registerOnBackInvokedCallback(
                 OnBackInvokedDispatcher.PRIORITY_DEFAULT,
                 new OnBackAnimationCallback() {
+
+                    @Nullable OnBackPressedHandler mActiveOnBackPressedHandler;
+
+                    @Override
+                    public void onBackStarted(@NonNull BackEvent backEvent) {
+                        if (mActiveOnBackPressedHandler != null) {
+                            mActiveOnBackPressedHandler.onBackCancelled();
+                        }
+                        mActiveOnBackPressedHandler = getOnBackPressedHandler();
+                        mActiveOnBackPressedHandler.onBackStarted();
+                    }
+
                     @Override
                     public void onBackInvoked() {
-                        onBackPressed();
+                        // Recreate mActiveOnBackPressedHandler if necessary to avoid NPE because:
+                        // 1. b/260636433: In 3-button-navigation mode, onBackStarted() is not
+                        // called on ACTION_DOWN before onBackInvoked() is called in ACTION_UP.
+                        // 2. Launcher#onBackPressed() will call onBackInvoked() without calling
+                        // onBackInvoked() beforehand.
+                        if (mActiveOnBackPressedHandler == null) {
+                            mActiveOnBackPressedHandler = getOnBackPressedHandler();
+                        }
+                        mActiveOnBackPressedHandler.onBackInvoked();
+                        mActiveOnBackPressedHandler = null;
                         TestLogging.recordEvent(TestProtocol.SEQUENCE_MAIN, "onBackInvoked");
                     }
 
                     @Override
                     public void onBackProgressed(@NonNull BackEvent backEvent) {
-                        QuickstepLauncher.this.onBackProgressed(backEvent.getProgress());
+                        if (!FeatureFlags.IS_STUDIO_BUILD && mActiveOnBackPressedHandler == null) {
+                            return;
+                        }
+                        mActiveOnBackPressedHandler
+                                .onBackProgressed(backEvent.getProgress());
                     }
 
                     @Override
                     public void onBackCancelled() {
-                        QuickstepLauncher.this.onBackCancelled();
+                        if (!FeatureFlags.IS_STUDIO_BUILD && mActiveOnBackPressedHandler == null) {
+                            return;
+                        }
+                        mActiveOnBackPressedHandler.onBackCancelled();
+                        mActiveOnBackPressedHandler = null;
                     }
                 });
     }

quickstep/src/com/android/quickstep/views/AllAppsEduView.java

@@ -111,11 +111,6 @@ public class AllAppsEduView extends AbstractFloatingView {
         return (type & TYPE_ALL_APPS_EDU) != 0;
     }
 
-    @Override
-    public boolean onBackPressed() {
-        return true;
-    }
-
     @Override
     public boolean canInterceptEventsInSystemGestureRegion() {
         return true;

src/com/android/launcher3/AbstractFloatingView.java

@@ -46,7 +46,8 @@ import java.lang.annotation.RetentionPolicy;
 /**
  * Base class for a View which shows a floating UI on top of the launcher UI.
  */
-public abstract class AbstractFloatingView extends LinearLayout implements TouchController {
+public abstract class AbstractFloatingView extends LinearLayout implements TouchController,
+        OnBackPressedHandler {
 
     @IntDef(flag = true, value = {
             TYPE_FOLDER,
@@ -165,12 +166,16 @@ public abstract class AbstractFloatingView extends LinearLayout implements Touch
 
     protected abstract boolean isOfType(@FloatingViewType int type);
 
-    /** @return Whether the back is consumed. If false, Launcher will handle the back as well. */
-    public boolean onBackPressed() {
-        close(true);
+    /** Return true if this view can consume back press. */
+    public boolean canHandleBack() {
         return true;
     }
 
+    @Override
+    public void onBackInvoked() {
+        close(true);
+    }
+
     @Override
     public boolean onControllerTouchEvent(MotionEvent ev) {
         return false;

src/com/android/launcher3/BaseDraggingActivity.java

@@ -125,9 +125,13 @@ public abstract class BaseDraggingActivity extends BaseActivity
         mCurrentActionMode = null;
     }
 
+    protected boolean isInAutoCancelActionMode() {
+        return mCurrentActionMode != null && AUTO_CANCEL_ACTION_MODE == mCurrentActionMode.getTag();
+    }
+
     @Override
     public boolean finishAutoCancelActionMode() {
-        if (mCurrentActionMode != null && AUTO_CANCEL_ACTION_MODE == mCurrentActionMode.getTag()) {
+        if (isInAutoCancelActionMode()) {
             mCurrentActionMode.finish();
             return true;
         }

src/com/android/launcher3/Launcher.java

@@ -560,6 +560,61 @@ public class Launcher extends StatefulActivity<LauncherState>
         setTitle(R.string.home_screen);
     }
 
+    /**
+     * Provide {@link OnBackPressedHandler} in below order:
+     * <ol>
+     *  <li> auto cancel action mode handler
+     *  <li> drag handler
+     *  <li> view handler
+     *  <li> state handler
+     * </ol>
+     *
+     * A back gesture (a single click on back button, or a swipe back gesture that contains a series
+     * of swipe events) should be handled by the same handler from above list. For a new back
+     * gesture, a new handler should be regenerated.
+     *
+     * Note that state handler will always be handling the back press event if the previous 3 don't.
+     */
+    @NonNull
+    protected OnBackPressedHandler getOnBackPressedHandler() {
+        // #1 auto cancel action mode handler
+        if (isInAutoCancelActionMode()) {
+            return this::finishAutoCancelActionMode;
+        }
+
+        // #2 drag handler
+        if (mDragController.isDragging()) {
+            return mDragController::cancelDrag;
+        }
+
+        // #3 view handler
+        AbstractFloatingView topView =
+                AbstractFloatingView.getTopOpenView(Launcher.this);
+        if (topView != null && topView.canHandleBack()) {
+            return topView;
+        }
+
+        // #4 state handler
+        return new OnBackPressedHandler() {
+            @Override
+            public void onBackInvoked() {
+                onStateBack();
+            }
+
+            @Override
+            public void onBackProgressed(
+                    @FloatRange(from = 0.0, to = 1.0) float backProgress) {
+                mStateManager.getState().onBackProgressed(
+                        Launcher.this, backProgress);
+            }
+
+            @Override
+            public void onBackCancelled() {
+                mStateManager.getState().onBackCancelled(Launcher.this);
+            }
+        };
+    }
+
     protected LauncherOverlayManager getDefaultOverlay() {
         return new LauncherOverlayManager() { };
     }
@@ -2047,36 +2102,13 @@ public class Launcher extends StatefulActivity<LauncherState>
 
     @Override
     public void onBackPressed() {
-        if (finishAutoCancelActionMode()) {
-            return;
-        }
-
-        if (mDragController.isDragging()) {
-            mDragController.cancelDrag();
-            return;
-        }
-
-        // Note: There should be at most one log per method call. This is enforced implicitly
-        // by using if-else statements.
-        AbstractFloatingView topView = AbstractFloatingView.getTopOpenView(this);
-        if (topView == null || !topView.onBackPressed()) {
-            // Not handled by the floating view.
-            onStateBack();
-        }
+        getOnBackPressedHandler().onBackInvoked();
     }
 
     protected void onStateBack() {
         mStateManager.getState().onBackPressed(this);
     }
 
-    protected void onBackProgressed(@FloatRange(from = 0.0, to = 1.0) float backProgress) {
-        mStateManager.getState().onBackProgressed(this, backProgress);
-    }
-
-    protected void onBackCancelled() {
-        mStateManager.getState().onBackCancelled(this);
-    }
-
     protected void onScreenOnChanged(boolean isOn) {
         // Reset AllApps to its initial state only if we are not in the middle of
         // processing a multi-step drop

src/com/android/launcher3/OnBackPressedHandler.java

@@ -0,0 +1,45 @@
+/*
+ * Copyright (C) 2023 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;
+
+import androidx.annotation.FloatRange;
+
+/**
+ * Interface that mimics {@link android.window.OnBackInvokedCallback} without dependencies on U's
+ * API such as {@link android.window.BackEvent}.
+ *
+ * <p> Impl can assume below order during a back gesture:
+ * <ol>
+ *  <li> [optional] one {@link #onBackStarted()} will be called to start the gesture
+ *  <li> zero or multiple {@link #onBackProgressed(float)} will be called during swipe gesture
+ *  <li> either one of {@link #onBackInvoked()} or {@link #onBackCancelled()} will be called to end
+ *  the gesture
+ */
+public interface OnBackPressedHandler {
+
+    /** Called when back has started. */
+    default void onBackStarted() {}
+
+    /** Called when back is committed. */
+    void onBackInvoked();
+
+    /** Called with back gesture's progress. */
+    default void onBackProgressed(@FloatRange(from = 0.0, to = 1.0) float backProgress) {}
+
+    /** Called when user drops the back gesture. */
+    default void onBackCancelled() {}
+}

src/com/android/launcher3/allapps/DiscoveryBounce.java

@@ -81,10 +81,10 @@ public class DiscoveryBounce extends AbstractFloatingView {
     }
 
     @Override
-    public boolean onBackPressed() {
-        super.onBackPressed();
-        // Go back to the previous state (from a user's perspective this floating view isn't
-        // something to go back from).
+    public boolean canHandleBack() {
+        // Since DiscoveryBounce doesn't handle back, onBackInvoked() won't be called and we should
+        // close it without animation.
+        close(false);
         return false;
     }
 

src/com/android/launcher3/folder/Folder.java

@@ -1579,17 +1579,14 @@ public class Folder extends AbstractFloatingView implements ClipPathView, DragSo
         return getOpenView(activityContext, TYPE_FOLDER);
     }
 
-    /**
-     * Navigation bar back key or hardware input back key has been issued.
-     */
+    /** Navigation bar back key or hardware input back key has been issued. */
     @Override
-    public boolean onBackPressed() {
+    public void onBackInvoked() {
         if (isEditingName()) {
             mFolderName.dispatchBackKey();
         } else {
-            super.onBackPressed();
+            super.onBackInvoked();
         }
-        return true;
     }
 
     @Override

src/com/android/launcher3/secondarydisplay/SecondaryDisplayLauncher.java

@@ -175,8 +175,9 @@ public class SecondaryDisplayLauncher extends BaseDraggingActivity
         // Note: There should be at most one log per method call. This is enforced implicitly
         // by using if-else statements.
         AbstractFloatingView topView = AbstractFloatingView.getTopOpenView(this);
-        if (topView != null && topView.onBackPressed()) {
+        if (topView != null && topView.canHandleBack()) {
             // Handled by the floating view.
+            topView.onBackInvoked();
         } else {
             showAppDrawer(false);
         }

src/com/android/launcher3/widget/picker/WidgetsFullSheet.java

@@ -17,7 +17,9 @@ package com.android.launcher3.widget.picker;
 
 import static android.view.View.MeasureSpec.makeMeasureSpec;
 
+import static com.android.launcher3.LauncherAnimUtils.SCALE_PROPERTY;
 import static com.android.launcher3.LauncherAnimUtils.VIEW_TRANSLATE_Y;
+import static com.android.launcher3.allapps.AllAppsTransitionController.SWIPE_ALL_APPS_TO_HOME_MIN_SCALE;
 import static com.android.launcher3.logging.StatsLogManager.LauncherEvent.LAUNCHER_WIDGETSTRAY_SEARCHED;
 import static com.android.launcher3.testing.shared.TestProtocol.NORMAL_STATE_ORDINAL;
 
@@ -45,6 +47,7 @@ import android.view.animation.Interpolator;
 import android.widget.Button;
 import android.widget.TextView;
 
+import androidx.annotation.FloatRange;
 import androidx.annotation.Nullable;
 import androidx.annotation.VisibleForTesting;
 import androidx.recyclerview.widget.DefaultItemAnimator;
@@ -54,6 +57,7 @@ import com.android.launcher3.Launcher;
 import com.android.launcher3.LauncherAppState;
 import com.android.launcher3.R;
 import com.android.launcher3.Utilities;
+import com.android.launcher3.anim.Interpolators;
 import com.android.launcher3.anim.PendingAnimation;
 import com.android.launcher3.compat.AccessibilityManagerCompat;
 import com.android.launcher3.model.UserManagerState;
@@ -264,6 +268,15 @@ public class WidgetsFullSheet extends BaseWidgetSheet
         attachScrollbarToRecyclerView(currentRecyclerView);
     }
 
+    @Override
+    public void onBackProgressed(@FloatRange(from = 0.0, to = 1.0) float progress) {
+        float deceleratedProgress =
+                Interpolators.PREDICTIVE_BACK_DECELERATED_EASE.getInterpolation(progress);
+        float scaleProgress = SWIPE_ALL_APPS_TO_HOME_MIN_SCALE
+                + (1 - SWIPE_ALL_APPS_TO_HOME_MIN_SCALE) * (1 - deceleratedProgress);
+        SCALE_PROPERTY.set(this, scaleProgress);
+    }
+
     private void attachScrollbarToRecyclerView(WidgetsRecyclerView recyclerView) {
         recyclerView.bindFastScrollbar();
         if (mCurrentWidgetsRecyclerView != recyclerView) {
@@ -736,12 +749,12 @@ public class WidgetsFullSheet extends BaseWidgetSheet
     }
 
     @Override
-    public boolean onBackPressed() {
+    public void onBackInvoked() {
         if (mIsInSearchMode) {
             mSearchBar.reset();
-            return true;
+        } else {
+            super.onBackInvoked();
         }
-        return super.onBackPressed();
     }
 
     @Override