Clean up null check for mBackNavigationController

Only need to check when calling startBackNavigation.

Bug: 131727607
Test: build/flash
Change-Id: Ib6b92a4019070bc711e7a1ea9462eaf2d404df42

services/core/java/com/android/server/wm/ActivityTaskManagerService.java

@@ -460,7 +460,6 @@ public class ActivityTaskManagerService extends IActivityTaskManager.Stub {
     KeyguardController mKeyguardController;
     private final ClientLifecycleManager mLifecycleManager;
 
-    @Nullable
     final BackNavigationController mBackNavigationController;
 
     private TaskChangeNotificationController mTaskChangeNotificationController;
@@ -847,8 +846,7 @@ public class ActivityTaskManagerService extends IActivityTaskManager.Stub {
         mTaskOrganizerController = mWindowOrganizerController.mTaskOrganizerController;
         mTaskFragmentOrganizerController =
                 mWindowOrganizerController.mTaskFragmentOrganizerController;
-        mBackNavigationController = BackNavigationController.isEnabled()
-                ? new BackNavigationController() : null;
+        mBackNavigationController = new BackNavigationController();
     }
 
     public void onSystemReady() {
@@ -1031,9 +1029,7 @@ public class ActivityTaskManagerService extends IActivityTaskManager.Stub {
             mLockTaskController.setWindowManager(wm);
             mTaskSupervisor.setWindowManager(wm);
             mRootWindowContainer.setWindowManager(wm);
-            if (mBackNavigationController != null) {
-                mBackNavigationController.setWindowManager(wm);
-            }
+            mBackNavigationController.setWindowManager(wm);
         }
     }
 
@@ -1852,9 +1848,6 @@ public class ActivityTaskManagerService extends IActivityTaskManager.Stub {
             IWindowFocusObserver observer, BackAnimationAdapter adapter) {
         mAmInternal.enforceCallingPermission(START_TASKS_FROM_RECENTS,
                 "startBackNavigation()");
-        if (mBackNavigationController == null) {
-            return null;
-        }
 
         return mBackNavigationController.startBackNavigation(observer, adapter);
     }

services/core/java/com/android/server/wm/BackNavigationController.java

@@ -65,12 +65,12 @@ class BackNavigationController {
     // TODO (b/241808055) Find a appropriate time to remove during refactor
     // Execute back animation with legacy transition system. Temporary flag for easier debugging.
     static final boolean ENABLE_SHELL_TRANSITIONS = WindowManagerService.sEnableShellTransitions;
+
     /**
-     * Returns true if the back predictability feature is enabled
+     * true if the back predictability feature is enabled
      */
-    static boolean isEnabled() {
-        return SystemProperties.getInt("persist.wm.debug.predictive_back", 1) != 0;
-    }
+    static final boolean sPredictBackEnable =
+            SystemProperties.getBoolean("persist.wm.debug.predictive_back", true);
 
     static boolean isScreenshotEnabled() {
         return SystemProperties.getInt("persist.wm.debug.predictive_back_screenshot", 0) != 0;
@@ -88,6 +88,9 @@ class BackNavigationController {
     @Nullable
     BackNavigationInfo startBackNavigation(
             IWindowFocusObserver observer, BackAnimationAdapter adapter) {
+        if (!sPredictBackEnable) {
+            return null;
+        }
         final WindowManagerService wmService = mWindowManagerService;
         mFocusObserver = observer;
 

services/core/java/com/android/server/wm/RootWindowContainer.java

@@ -840,11 +840,8 @@ class RootWindowContainer extends WindowContainer<DisplayContent>
         if (recentsAnimationController != null) {
             recentsAnimationController.checkAnimationReady(defaultDisplay.mWallpaperController);
         }
-        final BackNavigationController backNavigationController =
-                mWmService.mAtmService.mBackNavigationController;
-        if (backNavigationController != null) {
-            backNavigationController.checkAnimationReady(defaultDisplay.mWallpaperController);
-        }
+        mWmService.mAtmService.mBackNavigationController
+                .checkAnimationReady(defaultDisplay.mWallpaperController);
 
         for (int displayNdx = 0; displayNdx < mChildren.size(); ++displayNdx) {
             final DisplayContent displayContent = mChildren.get(displayNdx);

services/core/java/com/android/server/wm/WallpaperController.java

@@ -239,8 +239,7 @@ class WallpaperController {
 
     private boolean isBackNavigationTarget(WindowState w) {
         // The window is in animating by back navigation and set to show wallpaper.
-        final BackNavigationController controller = mService.mAtmService.mBackNavigationController;
-        return controller != null && controller.isWallpaperVisible(w);
+        return mService.mAtmService.mBackNavigationController.isWallpaperVisible(w);
     }
 
     /**
@@ -831,9 +830,7 @@ class WallpaperController {
 
             // If there was a pending back navigation animation that would show wallpaper, start
             // the animation due to it was skipped in previous surface placement.
-            if (mService.mAtmService.mBackNavigationController != null) {
-                mService.mAtmService.mBackNavigationController.startAnimation();
-            }
+            mService.mAtmService.mBackNavigationController.startAnimation();
             return true;
         }
         return false;