draw(Canvas canvas, float , float y) 
draw(Canvas canvas, float x, float y, Paint paint) 

<declare-styleable name="GIFVIEW">
    <!--gif文件引用-->
    <attr name="gifSrc" format="reference" />
    <!--是否加载完自动播放-->
    <attr name="authPlay" format="boolean" />
    <!--播放次放，默认永远播放-->
    <attr name="playCount" format="integer" />
  </declare-styleable>

public interface OnPlayListener {
    void onPlayStart();

    void onPlaying(int percent);

    void onPlayPause(boolean pauseSuccess);

    void onPlayRestart();

    void onPlayEnd();
  }

public class GifImageView extends AppCompatImageView

public void setGifResource(int movieResourceId, OnPlayListener onPlayListener) {
    mOnPlayListener = onPlayListener;
    movie = Movie.decodeStream(getResources().openRawResource(movieResourceId));
    if (movie == null) {
      //如果movie为空，那么就不是gif文件，尝试转换为bitmap显示
      Bitmap bitmap = BitmapFactory.decodeResource(getResources(), movieResourceId);
      if (bitmap != null) {
        setImageBitmap(bitmap);
        return;
      }
    }
    movieDuration = movie.duration() == 0 ? DEFAULT_DURATION : movie.duration();
    requestLayout();
  }

@Override
  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    if (movie != null) {
      int movieWidth = movie.width();
      int movieHeight = movie.height();
      setMeasuredDimension(movieWidth, movieHeight);
    } else {
      super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    }
  }

public void play(int counts) {
    this.counts = counts;
    reset();
    if (mOnPlayListener != null) {
      mOnPlayListener.onPlayStart();
    }
    invalidate();
  }

@Override
  protected void onDraw(Canvas canvas) {
    if (movie != null) {
      if (!mPaused && hasStart) {
        drawMovieFrame(canvas);
        invalidateView();
      } else {
        drawMovieFrame(canvas);
      }
    } else {
      super.onDraw(canvas);
    }
  }
  /**
   * 画出gif帧
   */
  private void drawMovieFrame(Canvas canvas) {
    movie.setTime(getCurrentFrameTime());
    movie.draw(canvas, 0.0f, 0.0f);
  }

private int getCurrentFrameTime() {
    if (movieDuration == 0)
      return 0;
      //因为有暂停，所以需要减去暂停时间
    long now = SystemClock.uptimeMillis() - dealyTime;
    int nowCount = (int) ((now - mMovieStart) / movieDuration);
    if (counts != -1 && nowCount >= counts) {
      hasStart = false;
      if (mOnPlayListener != null) {
        mOnPlayListener.onPlayEnd();
      }
    }
    int currentTime = (int) ((now - mMovieStart) % movieDuration);
    int percent = currentTime * 100 / movieDuration;
    if (mOnPlayListener != null && hasStart) {
      mOnPlayListener.onPlaying(percent);
    }
    return currentTime;
  }

public void pause() {
    if (movie != null && !mPaused && hasStart) {
      mPaused = true;
      invalidate();
      mMoviePauseTime = SystemClock.uptimeMillis();
      if (mOnPlayListener != null) {
        mOnPlayListener.onPlayPause(true);
      }
    } else {
      if (mOnPlayListener != null) {
        mOnPlayListener.onPlayPause(false);
      }
    }
  }

if (mPaused && mMoviePauseTime > 0) {
        mPaused = false;
        dealyTime = dealyTime + SystemClock.uptimeMillis() - mMoviePauseTime;
        invalidate();
        if (mOnPlayListener != null) {
          mOnPlayListener.onPlayRestart();
        }
      }
经过这些处理，我们就

public void playReserver() {
    if (movie != null) {
      reset();
      reverse = true;
      if (mOnPlayListener != null) {
        mOnPlayListener.onPlayStart();
      }
      invalidate();
    }
  }

if (reverse) {
          movie.setTime(movieDuration - getCurrentFrameTime());
        } else {
          movie.setTime(getCurrentFrameTime());
        }