Add TaskAdapter to recents Go.

This CL adds a recycler view adapter for tasks to manage the item
control logic. The data source itself and view hierarchy is planned to
be added in future CLs.

Bug: 114136250
Test: Build l3GoIconRecents
Change-Id: I72d4f9df68d17fd745947d36522cde342ea58317

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

@@ -0,0 +1,58 @@
+/*
+ * 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;
+
+import android.view.ViewGroup;
+import android.widget.TextView;
+
+import androidx.annotation.NonNull;
+import androidx.recyclerview.widget.RecyclerView.Adapter;
+
+import com.android.systemui.shared.recents.model.Task;
+
+import java.util.ArrayList;
+
+/**
+ * Recycler view adapter that dynamically inflates and binds {@link TaskHolder} instances with the
+ * appropriate {@link Task} from the recents task list.
+ */
+public final class TaskAdapter extends Adapter<TaskHolder> {
+
+    private static final int MAX_TASKS_TO_DISPLAY = 6;
+    private static final String TAG = "TaskAdapter";
+    private final ArrayList<Task> mTaskList;
+
+    public TaskAdapter(@NonNull ArrayList<Task> taskList) {
+        mTaskList = taskList;
+    }
+
+    @Override
+    public TaskHolder onCreateViewHolder(ViewGroup parent, int viewType) {
+        // TODO: Swap in an actual task view here (view w/ icon, label, etc.)
+        TextView stubView = new TextView(parent.getContext());
+        return new TaskHolder(stubView);
+    }
+
+    @Override
+    public void onBindViewHolder(TaskHolder holder, int position) {
+        holder.bindTask(mTaskList.get(position));
+    }
+
+    @Override
+    public int getItemCount() {
+        return Math.min(mTaskList.size(), MAX_TASKS_TO_DISPLAY);
+    }
+}

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

@@ -0,0 +1,48 @@
+/*
+ * 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;
+
+import android.widget.TextView;
+
+import androidx.recyclerview.widget.RecyclerView.ViewHolder;
+
+import com.android.systemui.shared.recents.model.Task;
+
+/**
+ * A recycler view holder that holds the task view and binds {@link Task} content (app title, icon,
+ * etc.) to the view.
+ */
+final class TaskHolder extends ViewHolder {
+
+    // TODO: Implement the actual task view to be held.
+    // For now, we just use a simple text view.
+    private final TextView mStubView;
+
+    public TaskHolder(TextView stubView) {
+        super(stubView);
+        mStubView = stubView;
+    }
+
+    /**
+     * Bind task content to the view. This includes the task icon and title as well as binding
+     * input handlers such as which task to launch/remove.
+     *
+     * @param task the task to bind to the view this
+     */
+    public void bindTask(Task task) {
+        mStubView.setText("Stub task view: " + task.titleDescription);
+    }
+}

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

@@ -21,8 +21,14 @@ import android.util.FloatProperty;
 import android.view.ViewDebug;
 import android.widget.FrameLayout;
 
+import com.android.quickstep.TaskAdapter;
+import com.android.systemui.shared.recents.model.Task;
+
+import java.util.ArrayList;
+
 /**
- * Root view for the icon recents view.
+ * Root view for the icon recents view. Acts as the main interface to the rest of the Launcher code
+ * base.
  */
 public final class IconRecentsView extends FrameLayout {
 
@@ -58,12 +64,24 @@ public final class IconRecentsView extends FrameLayout {
      * is top aligned and 0.5 is centered vertically.
      */
     @ViewDebug.ExportedProperty(category = "launcher")
+
+    // TODO: Write a recents task list observer that creates/updates tasks and signals task adapter.
+    private static final ArrayList<Task> DUMMY_TASK_LIST = new ArrayList<>();
+
     private float mTranslationYFactor;
+    private TaskAdapter mTaskAdapter;
 
     public IconRecentsView(Context context, AttributeSet attrs) {
         super(context, attrs);
     }
 
+    @Override
+    protected void onFinishInflate() {
+        super.onFinishInflate();
+        mTaskAdapter = new TaskAdapter(DUMMY_TASK_LIST);
+        // TODO: Hook task adapter up to recycler view.
+    }
+
     public void setTranslationYFactor(float translationFactor) {
         mTranslationYFactor = translationFactor;
         setTranslationY(computeTranslationYForFactor(mTranslationYFactor));