content: /*
   * Copyright (C) 2010 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 android.animation;
  
  import android.view.animation.AnimationUtils;
  
  /**
   * This class provides a simple callback mechanism to listeners that is synchronized with all
   * other animators in the system. There is no duration, interpolation, or object value-setting
   * with this Animator. Instead, it is simply started, after which it proceeds to send out events
   * on every animation frame to its TimeListener (if set), with information about this animator,
   * the total elapsed time, and the elapsed time since the previous animation frame.
   */
  public class TimeAnimator extends ValueAnimator {
  
      private TimeListener mListener;
      private long mPreviousTime = -1;
  
      @Override
      public void start() {
          mPreviousTime = -1;
          super.start();
      }
  
      @Override
      boolean animateBasedOnTime(long currentTime) {
          if (mListener != null) {
              long totalTime = currentTime - mStartTime;
              long deltaTime = (mPreviousTime < 0) ? 0 : (currentTime - mPreviousTime);
              mPreviousTime = currentTime;
              mListener.onTimeUpdate(this, totalTime, deltaTime);
          }
          return false;
      }
  
      @Override
      public void setCurrentPlayTime(long playTime) {
          long currentTime = AnimationUtils.currentAnimationTimeMillis();
          mStartTime = Math.max(mStartTime, currentTime - playTime);
          mStartTimeCommitted = true; // do not allow start time to be compensated for jank
          animateBasedOnTime(currentTime);
      }
  
      /**
       * Sets a listener that is sent update events throughout the life of
       * an animation.
       *
       * @param listener the listener to be set.
       */
      public void setTimeListener(TimeListener listener) {
          mListener = listener;
      }
  
      @Override
      void animateValue(float fraction) {
          // Noop
      }
  
      @Override
      void initAnimation() {
          // noop
      }
  
      /**
       * Implementors of this interface can set themselves as update listeners
       * to a <code>TimeAnimator</code> instance to receive callbacks on every animation
       * frame to receive the total time since the animator started and the delta time
       * since the last frame. The first time the listener is called,
       * deltaTime will be zero. The same is true for totalTime, unless the animator was
       * set to a specific {@link ValueAnimator#setCurrentPlayTime(long) currentPlayTime}
       * prior to starting.
       */
      public static interface TimeListener {
          /**
           * <p>Notifies listeners of the occurrence of another frame of the animation,
           * along with information about the elapsed time.</p>
           *
           * @param animation The animator sending out the notification.
           * @param totalTime The total time elapsed since the animator started, in milliseconds.
           * @param deltaTime The time elapsed since the previous frame, in milliseconds.
           */
          void onTimeUpdate(TimeAnimator animation, long totalTime, long deltaTime);
  
      }
  }
  