content: /**
   * Copyright (C) 2015 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.util;
  
  import android.os.Process;
  import android.view.View;
  import android.view.View.OnAttachStateChangeListener;
  import android.view.ViewTreeObserver.OnDrawListener;
  
  import com.android.launcher3.Launcher;
  import com.android.launcher3.LauncherModel;
  
  import java.util.ArrayList;
  import java.util.concurrent.Executor;
  
  /**
   * An executor which runs all the tasks after the first onDraw is called on the target view.
   */
  public class ViewOnDrawExecutor implements Executor, OnDrawListener, Runnable,
          OnAttachStateChangeListener {
  
      private final ArrayList<Runnable> mTasks = new ArrayList<>();
      private final Executor mExecutor;
  
      private Launcher mLauncher;
      private View mAttachedView;
      private boolean mCompleted;
      private boolean mIsExecuting;
  
      private boolean mLoadAnimationCompleted;
      private boolean mFirstDrawCompleted;
  
      public ViewOnDrawExecutor(Executor executor) {
          mExecutor = executor;
      }
  
      public void attachTo(Launcher launcher) {
          mLauncher = launcher;
          mAttachedView = launcher.getWorkspace();
          mAttachedView.addOnAttachStateChangeListener(this);
  
          attachObserver();
      }
  
      private void attachObserver() {
          if (!mCompleted) {
              mAttachedView.getViewTreeObserver().addOnDrawListener(this);
          }
      }
  
      @Override
      public void execute(Runnable command) {
          mTasks.add(command);
          LauncherModel.setWorkerPriority(Process.THREAD_PRIORITY_BACKGROUND);
      }
  
      @Override
      public void onViewAttachedToWindow(View v) {
          attachObserver();
      }
  
      @Override
      public void onViewDetachedFromWindow(View v) { }
  
      @Override
      public void onDraw() {
          mFirstDrawCompleted = true;
          mAttachedView.post(this);
      }
  
      /**
       * Returns whether the executor is still queuing tasks and hasn't yet executed them.
       */
      public boolean canQueue() {
          return !mIsExecuting && !mCompleted;
      }
  
      public void onLoadAnimationCompleted() {
          mLoadAnimationCompleted = true;
          if (mAttachedView != null) {
              mAttachedView.post(this);
          }
      }
  
      @Override
      public void run() {
          // Post the pending tasks after both onDraw and onLoadAnimationCompleted have been called.
          if (mLoadAnimationCompleted && mFirstDrawCompleted && !mCompleted) {
              mIsExecuting = true;
              for (final Runnable r : mTasks) {
                  mExecutor.execute(r);
              }
              markCompleted();
          }
      }
  
      public void markCompleted() {
          mTasks.clear();
          mCompleted = true;
          mIsExecuting = false;
          if (mAttachedView != null) {
              mAttachedView.getViewTreeObserver().removeOnDrawListener(this);
              mAttachedView.removeOnAttachStateChangeListener(this);
          }
          if (mLauncher != null) {
              mLauncher.clearPendingExecutor(this);
          }
          LauncherModel.setWorkerPriority(Process.THREAD_PRIORITY_DEFAULT);
      }
  }
  