Android实现ImageView图片双击放大及缩小

public class DoubleScaleImageView extends ImageView implements OnTouchListener, OnGlobalLayoutListener {
  private boolean isFirst = false;
  private float doubleScale;// 双击放大的值
  private Matrix mScaleMatrix;
  private float defaultScale;// 默认的缩放值
  private int mLastPinterCount;// 记录上一次多点触控的数量
  private float mLastX;
  private float mLastY;
  private int mTouchSlop;
  private boolean isCanDrag;
  private boolean isCheckLeft;
  private boolean isCheckTop;
  private GestureDetector mGestureDetector;
  public DoubleScaleImageView(Context context) {
    this(context, null);
  }
  public DoubleScaleImageView(Context context, AttributeSet attrs) {
    this(context, attrs, 0);
  }
  @SuppressLint("ClickableViewAccessibility")
  public DoubleScaleImageView(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    mScaleMatrix = new Matrix();
    setScaleType(ScaleType.MATRIX);
    setOnTouchListener(this);
    // getScaledTouchSlop是一个距离，表示滑动的时候，手的移动要大于这个距离才开始移动控件。如果小于这个距离就不触发移动控件
    mTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop();
    mGestureDetector = new GestureDetector(context, new GestureDetector.SimpleOnGestureListener() {
      @Override
      public boolean onDoubleTap(MotionEvent e) {
        float x = e.getX();
        float y = e.getY();
        if (getScale()  width && imageHeight  height) {
        scale = height * 1.0f / imageHeight;
      }
      // 如果图片的宽度都 大于或小于控件宽度，我们则要对图片进行对应缩放，保证图片占满控件
      if ((imageWidth > width && imageHeight > height) || (imageWidth  0 && isCheckTop) {
      delY = -rectf.top;
    }
    if (rectf.bottom  0 && isCheckLeft) {
      delX = -rectf.left;
    }
    if (rectf.right  mTouchSlop;
  }
  /**
   * 获取图片的位置
   * @description：
   * @date 2016-1-8 上午9:02:10
   */
  private RectF getMatrixRectf() {
    Matrix matrix = mScaleMatrix;
    RectF recft = new RectF();
    if (getDrawable() != null) {
      recft.set(0, 0, getDrawable().getIntrinsicWidth(), getDrawable().getIntrinsicHeight());
      matrix.mapRect(recft);
    }
    return recft;
  }

  // 获取当前图片的缩放值
  private float getScale() {
    float values[] = new float[9];
    mScaleMatrix.getValues(values);
    return values[Matrix.MSCALE_X];
  }
}