Control logic for putting up loading UI

This CL introduces the logic to put up and bind loading task views while
the first phase of loading occurs (i.e. loading the number and order of
recents items).

Bug: 114136250
Test: Go to recents, see tasks loading
Change-Id: I59bdc0fccc7f309ea4cded175c04a464b5a3665e

go/quickstep/src/com/android/quickstep/TaskActionController.java

@@ -42,6 +42,9 @@ public final class TaskActionController {
      * @param viewHolder the task view holder to launch
      */
     public void launchTask(TaskHolder viewHolder) {
+        if (viewHolder.getTask() == null) {
+            return;
+        }
         TaskItemView itemView = (TaskItemView) (viewHolder.itemView);
         View v = itemView.getThumbnailView();
         int left = 0;
@@ -60,6 +63,9 @@ public final class TaskActionController {
      * @param viewHolder the task view holder to remove
      */
     public void removeTask(TaskHolder viewHolder) {
+        if (viewHolder.getTask() == null) {
+            return;
+        }
         int position = viewHolder.getAdapterPosition();
         Task task = viewHolder.getTask();
         ActivityManagerWrapper.getInstance().removeTask(task.key.id);

go/quickstep/src/com/android/quickstep/TaskAdapter.java

@@ -28,6 +28,7 @@ import com.android.quickstep.views.TaskItemView;
 import com.android.systemui.shared.recents.model.Task;
 
 import java.util.List;
+import java.util.Objects;
 
 /**
  * Recycler view adapter that dynamically inflates and binds {@link TaskHolder} instances with the
@@ -40,6 +41,7 @@ public final class TaskAdapter extends Adapter<TaskHolder> {
     private final TaskListLoader mLoader;
     private final ArrayMap<Integer, TaskItemView> mTaskIdToViewMap = new ArrayMap<>();
     private TaskActionController mTaskActionController;
+    private boolean mIsShowingLoadingUi;
 
     public TaskAdapter(@NonNull TaskListLoader loader) {
         mLoader = loader;
@@ -49,6 +51,18 @@ public final class TaskAdapter extends Adapter<TaskHolder> {
         mTaskActionController = taskActionController;
     }
 
+    /**
+     * Sets all positions in the task adapter to loading views, binding new views if necessary.
+     * This changes the task adapter's view of the data, so the appropriate notify events should be
+     * called in addition to this method to reflect the changes.
+     *
+     * @param isShowingLoadingUi true to bind loading task views to all positions, false to return
+     *                           to the real data
+     */
+    public void setIsShowingLoadingUi(boolean isShowingLoadingUi) {
+        mIsShowingLoadingUi = isShowingLoadingUi;
+    }
+
     /**
      * Get task item view for a given task id if it's attached to the view.
      *
@@ -70,6 +84,10 @@ public final class TaskAdapter extends Adapter<TaskHolder> {
 
     @Override
     public void onBindViewHolder(TaskHolder holder, int position) {
+        if (mIsShowingLoadingUi) {
+            holder.bindEmptyUi();
+            return;
+        }
         List<Task> tasks = mLoader.getCurrentTaskList();
         if (position >= tasks.size()) {
             // Task list has updated.
@@ -79,13 +97,13 @@ public final class TaskAdapter extends Adapter<TaskHolder> {
         holder.bindTask(task);
         mLoader.loadTaskIconAndLabel(task, () -> {
             // Ensure holder still has the same task.
-            if (task.equals(holder.getTask())) {
+            if (Objects.equals(task, holder.getTask())) {
                 holder.getTaskItemView().setIcon(task.icon);
                 holder.getTaskItemView().setLabel(task.titleDescription);
             }
         });
         mLoader.loadTaskThumbnail(task, () -> {
-            if (task.equals(holder.getTask())) {
+            if (Objects.equals(task, holder.getTask())) {
                 holder.getTaskItemView().setThumbnail(task.thumbnail.thumbnail);
             }
         });
@@ -93,16 +111,27 @@ public final class TaskAdapter extends Adapter<TaskHolder> {
 
     @Override
     public void onViewAttachedToWindow(@NonNull TaskHolder holder) {
+        if (holder.getTask() == null) {
+            return;
+        }
         mTaskIdToViewMap.put(holder.getTask().key.id, (TaskItemView) holder.itemView);
     }
 
     @Override
     public void onViewDetachedFromWindow(@NonNull TaskHolder holder) {
+        if (holder.getTask() == null) {
+            return;
+        }
         mTaskIdToViewMap.remove(holder.getTask().key.id);
     }
 
     @Override
     public int getItemCount() {
+        if (mIsShowingLoadingUi) {
+            // Show loading version of all items.
+            return MAX_TASKS_TO_DISPLAY;
+        } else {
             return Math.min(mLoader.getCurrentTaskList().size(), MAX_TASKS_TO_DISPLAY);
         }
+    }
 }

go/quickstep/src/com/android/quickstep/TaskHolder.java

@@ -15,7 +15,7 @@
  */
 package com.android.quickstep;
 
-import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 import androidx.recyclerview.widget.RecyclerView.ViewHolder;
 
 import com.android.quickstep.views.TaskItemView;
@@ -50,11 +50,23 @@ public final class TaskHolder extends ViewHolder {
     }
 
     /**
-     * Gets the task currently bound to this view
+     * Bind a generic empty UI to the holder to make it clear that the item is loading/unbound and
+     * should not be expected to react to user input.
+     */
+    public void bindEmptyUi() {
+        mTask = null;
+        // TODO: Set the task view to a loading, empty UI.
+        // Temporarily using the one below for visual confirmation but should be swapped out to new
+        // UI later.
+        mTaskItemView.resetTaskItemView();
+    }
+
+    /**
+     * Gets the task currently bound to this view. May be null if task holder is in a loading state.
      *
      * @return the current task
      */
-    public @NonNull Task getTask() {
+    public @Nullable Task getTask() {
         return mTask;
     }
 }

go/quickstep/src/com/android/quickstep/views/IconRecentsView.java

@@ -157,10 +157,12 @@ public final class IconRecentsView extends FrameLayout {
      * becomes visible.
      */
     public void onBeginTransitionToOverview() {
+        mTaskAdapter.setIsShowingLoadingUi(true);
+        mTaskAdapter.notifyDataSetChanged();
         // Load any task changes
         mTaskLoader.loadTaskList(tasks -> {
-            // TODO: Put up some loading UI while task content is loading. May have to do something
-            // smarter when animating from app to overview.
+            mTaskAdapter.setIsShowingLoadingUi(false);
+            // TODO: Animate the loading UI out and the loaded data in.
             mTaskAdapter.notifyDataSetChanged();
         });
     }