Add support for sticky placeholders am: b777d3581c

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/16169736

Change-Id: Ifafdb32ba32de01702b75db6b9abcef6d305f754

libs/WindowManager/Jetpack/src/androidx/window/extensions/embedding/SplitContainer.java

@@ -84,6 +84,13 @@ class SplitContainer {
         return shouldFinishSecondaryWithPrimary || isPlaceholderContainer;
     }
 
+    static boolean isStickyPlaceholderRule(@NonNull SplitRule splitRule) {
+        if (!(splitRule instanceof SplitPlaceholderRule)) {
+            return false;
+        }
+        return ((SplitPlaceholderRule) splitRule).isSticky();
+    }
+
     @Override
     public String toString() {
         return "SplitContainer{"

libs/WindowManager/Jetpack/src/androidx/window/extensions/embedding/SplitController.java

@@ -16,6 +16,8 @@
 
 package androidx.window.extensions.embedding;
 
+import static androidx.window.extensions.embedding.SplitContainer.isStickyPlaceholderRule;
+
 import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.app.Activity;
@@ -460,6 +462,11 @@ public class SplitController implements JetpackTaskFragmentOrganizer.TaskFragmen
             return false;
         }
 
+        if (isStickyPlaceholderRule(splitContainer.getSplitRule())) {
+            // The placeholder should remain after it was first shown.
+            return false;
+        }
+
         if (mPresenter.shouldShowSideBySide(splitContainer)) {
             return false;
         }
@@ -643,6 +650,46 @@ public class SplitController implements JetpackTaskFragmentOrganizer.TaskFragmen
         return false;
     }
 
+    /**
+     * Checks whether the associated container should be destroyed together with a finishing
+     * container. There is a case when primary containers for placeholders should be retained
+     * despite the rule configuration to finish primary with secondary - if they are marked as
+     * 'sticky' and the placeholder was finished when fully overlapping the primary container.
+     * @return {@code true} if the associated container should be retained (and not be finished).
+     */
+    boolean shouldRetainAssociatedContainer(@NonNull TaskFragmentContainer finishingContainer,
+            @NonNull TaskFragmentContainer associatedContainer) {
+        SplitContainer splitContainer = getActiveSplitForContainers(associatedContainer,
+                finishingContainer);
+        if (splitContainer == null) {
+            // Containers are not in the same split, no need to retain.
+            return false;
+        }
+
+        if (!isStickyPlaceholderRule(splitContainer.getSplitRule())) {
+            // Currently only the containers associated with sticky placeholders can be retained.
+            return false;
+        }
+
+        // When sticky placeholder is stacked on top of the main container it should not cause the
+        // destruction of the primary one.
+        return !mPresenter.shouldShowSideBySide(splitContainer);
+    }
+
+    /**
+     * @see #shouldRetainAssociatedContainer(TaskFragmentContainer, TaskFragmentContainer)
+     */
+    boolean shouldRetainAssociatedActivity(@NonNull TaskFragmentContainer finishingContainer,
+            @NonNull Activity associatedActivity) {
+        TaskFragmentContainer associatedContainer = getContainerWithActivity(
+                associatedActivity.getActivityToken());
+        if (associatedContainer == null) {
+            return false;
+        }
+
+        return shouldRetainAssociatedContainer(finishingContainer, associatedContainer);
+    }
+
     private final class LifecycleCallbacks implements ActivityLifecycleCallbacks {
 
         @Override

libs/WindowManager/Jetpack/src/androidx/window/extensions/embedding/TaskFragmentContainer.java

@@ -228,6 +228,9 @@ class TaskFragmentContainer {
 
         // Finish dependent containers
         for (TaskFragmentContainer container : mContainersToFinishOnExit) {
+            if (controller.shouldRetainAssociatedContainer(this, container)) {
+                continue;
+            }
             container.finish(true /* shouldFinishDependent */, presenter,
                     wct, controller);
         }
@@ -235,6 +238,9 @@ class TaskFragmentContainer {
 
         // Finish associated activities
         for (Activity activity : mActivitiesToFinishOnExit) {
+            if (controller.shouldRetainAssociatedActivity(this, activity)) {
+                continue;
+            }
             activity.finish();
         }
         mActivitiesToFinishOnExit.clear();