Android实现手势控制ImageView图片大小

本文实例实现的主要功能是在ImageView中识别手势用以控制图片放大或缩小，具有一定的参考价值，分享给大家。

public class MatrixImageView extends ImageView {
  private GestureDetector mGestureDetector;
  private Matrix mMatrix = new Matrix();
  private float mImageWidth;
  private float mImageHeight;
  private float mScale;
  private OnMovingListener mMoveListener;
  private OnSingleTapListener mSingleTapListener;
  public MatrixImageView(Context context, AttributeSet attrs) {
    super(context, attrs);
    init();
  }
  public MatrixImageView(Context context) {
    super(context, null);
    init();
  }
  private void init() {
    MatrixTouchListener listener = new MatrixTouchListener();
    setOnTouchListener(listener);
    mGestureDetector = new GestureDetector(getContext(),
        new GestureListener(listener));
    setBackgroundColor(Color.BLACK);
    setScaleType(ScaleType.FIT_CENTER);
  }
  public void setOnMovingListener(OnMovingListener listener) {
    mMoveListener = listener;
  }
  public void setOnSingleTapListener(OnSingleTapListener onSingleTapListener) {
    this.mSingleTapListener = onSingleTapListener;
  }
  @Override
  public void setImageBitmap(Bitmap bm) {
    super.setImageBitmap(bm);
    if (getWidth() == 0) {
      ViewTreeObserver vto = getViewTreeObserver();
      vto.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
        public boolean onPreDraw() {
          initData();
          MatrixImageView.this.getViewTreeObserver()
              .removeOnPreDrawListener(this);
          return true;
        }
      });
    } else {
      initData();
    }
  }
  private void initData() {
    mMatrix.set(getImageMatrix());
    float[] values = new float[9];
    mMatrix.getValues(values);
    mImageWidth = getWidth() / values[Matrix.MSCALE_X];
    mImageHeight = (getHeight() - values[Matrix.MTRANS_Y] * 2)
        / values[Matrix.MSCALE_Y];
    mScale = values[Matrix.MSCALE_X];
  }
  public class MatrixTouchListener implements OnTouchListener {
    private static final int MODE_DRAG = 1;
    private static final int MODE_ZOOM = 2;
    private static final int MODE_UNABLE = 3;
    private static final float MAX_SCALE = 6;
    private static final float DOUBLE_CLICK_SACLE = 2;
    private int mMode = 0;
    private float mStartDis;
    private Matrix mCurrentMatrix = new Matrix();
    private boolean mLeftDragable;
    private boolean mRightDragable;
    private boolean mFirstMove = false;
    private PointF mStartPoint = new PointF();
    @Override
    public boolean onTouch(View v, MotionEvent event) {
      switch (event.getActionMasked()) {
      case MotionEvent.ACTION_DOWN:
        mMode = MODE_DRAG;
        mStartPoint.set(event.getX(), event.getY());
        isMatrixEnable();
        startDrag();
        checkDragable();
        break;
      case MotionEvent.ACTION_UP:
      case MotionEvent.ACTION_CANCEL:
        reSetMatrix();
        stopDrag();
        break;
      case MotionEvent.ACTION_MOVE:
        if (mMode == MODE_ZOOM) {
          setZoomMatrix(event);
        } else if (mMode == MODE_DRAG) {
          setDragMatrix(event);
        } else {
          stopDrag();
        }
        break;
      case MotionEvent.ACTION_POINTER_DOWN:
        if (mMode == MODE_UNABLE)
          return true;
        mMode = MODE_ZOOM;
        mStartDis = distance(event);
        break;
      case MotionEvent.ACTION_POINTER_UP:
        break;
      default:
        break;
      }
      return mGestureDetector.onTouchEvent(event);
    }
    private void startDrag() {
      if (mMoveListener != null)
        mMoveListener.startDrag();
    }
    private void stopDrag() {
      if (mMoveListener != null)
        mMoveListener.stopDrag();
    }
    private void checkDragable() {
      mLeftDragable = true;
      mRightDragable = true;
      mFirstMove = true;
      float[] values = new float[9];
      getImageMatrix().getValues(values);
      if (values[Matrix.MTRANS_X] >= 0)
        mRightDragable = false;
      if ((mImageWidth) * values[Matrix.MSCALE_X]
          + values[Matrix.MTRANS_X] <= getWidth()) {
        mLeftDragable = false;
      }
    }
    public void setDragMatrix(MotionEvent event) {
      if (isZoomChanged()) {
        float dx = event.getX() - mStartPoint.x;
        float dy = event.getY() - mStartPoint.y;
        if (Math.sqrt(dx * dx + dy * dy) > 10f) {
          mStartPoint.set(event.getX(), event.getY());
          mCurrentMatrix.set(getImageMatrix());
          float[] values = new float[9];
          mCurrentMatrix.getValues(values);
          dy = checkDyBound(values, dy);
          dx = checkDxBound(values, dx, dy);
          mCurrentMatrix.postTranslate(dx, dy);
          setImageMatrix(mCurrentMatrix);
        }
      } else {
        stopDrag();
      }
    }
    private boolean isZoomChanged() {
      float[] values = new float[9];
      getImageMatrix().getValues(values);
      float scale = values[Matrix.MSCALE_X];
      return scale != mScale;
    }
    private float checkDyBound(float[] values, float dy) {
      float height = getHeight();
      if (mImageHeight * values[Matrix.MSCALE_Y] < height)
        return 0;
      if (values[Matrix.MTRANS_Y] + dy > 0)
        dy = -values[Matrix.MTRANS_Y];
      else if (values[Matrix.MTRANS_Y] + dy < -(mImageHeight
          * values[Matrix.MSCALE_Y] - height))
        dy = -(mImageHeight * values[Matrix.MSCALE_Y] - height)
            - values[Matrix.MTRANS_Y];
      return dy;
    }
    private float checkDxBound(float[] values, float dx, float dy) {
      float width = getWidth();
      if (!mLeftDragable && dx < 0) {
        if (Math.abs(dx) * 0.4f > Math.abs(dy) && mFirstMove) {
          stopDrag();
        }
        return 0;
      }
      if (!mRightDragable && dx > 0) {
        if (Math.abs(dx) * 0.4f > Math.abs(dy) && mFirstMove) {
          stopDrag();
        }
        return 0;
      }
      mLeftDragable = true;
      mRightDragable = true;
      if (mFirstMove)
        mFirstMove = false;
      if (mImageWidth * values[Matrix.MSCALE_X] < width) {
        return 0;
      }
      if (values[Matrix.MTRANS_X] + dx > 0) {
        dx = -values[Matrix.MTRANS_X];
      } else if (values[Matrix.MTRANS_X] + dx < -(mImageWidth
          * values[Matrix.MSCALE_X] - width)) {
        dx = -(mImageWidth * values[Matrix.MSCALE_X] - width)
            - values[Matrix.MTRANS_X];
      }
      return dx;
    }
    private void setZoomMatrix(MotionEvent event) {
      if (event.getPointerCount() < 2)
        return;
      float endDis = distance(event);
      if (endDis > 10f) {
        float scale = endDis / mStartDis;
        mStartDis = endDis;
        mCurrentMatrix.set(getImageMatrix());
        float[] values = new float[9];
        mCurrentMatrix.getValues(values);
        scale = checkMaxScale(scale, values);
        PointF centerF = getCenter(scale, values);
        mCurrentMatrix.postScale(scale, scale, centerF.x, centerF.y);
        setImageMatrix(mCurrentMatrix);
      }
    }
    private PointF getCenter(float scale, float[] values) {
      if (scale * values[Matrix.MSCALE_X] < mScale || scale >= 1) {
        return new PointF(getWidth() / 2, getHeight() / 2);
      }
      float cx = getWidth() / 2;
      float cy = getHeight() / 2;
      if ((getWidth() / 2 - values[Matrix.MTRANS_X]) * scale < getWidth() / 2)
        cx = 0;
      if ((mImageWidth * values[Matrix.MSCALE_X] + values[Matrix.MTRANS_X])
          * scale < getWidth())
        cx = getWidth();
      return new PointF(cx, cy);
    }
    private float checkMaxScale(float scale, float[] values) {
      if (scale * values[Matrix.MSCALE_X] > MAX_SCALE)
        scale = MAX_SCALE / values[Matrix.MSCALE_X];
      return scale;
    }
    private void reSetMatrix() {
      if (checkRest()) {
        mCurrentMatrix.set(mMatrix);
        setImageMatrix(mCurrentMatrix);
      } else {
        float[] values = new float[9];
        getImageMatrix().getValues(values);
        float height = mImageHeight * values[Matrix.MSCALE_Y];
        if (height < getHeight()) {
          float topMargin = (getHeight() - height) / 2;
          if (topMargin != values[Matrix.MTRANS_Y]) {
            mCurrentMatrix.set(getImageMatrix());
            mCurrentMatrix.postTranslate(0, topMargin
                - values[Matrix.MTRANS_Y]);
            setImageMatrix(mCurrentMatrix);
          }
        }
      }
    }
    private boolean checkRest() {
      float[] values = new float[9];
      getImageMatrix().getValues(values);
      float scale = values[Matrix.MSCALE_X];
      return scale < mScale;
    }
    private void isMatrixEnable() {
      if (getScaleType() != ScaleType.CENTER) {
        setScaleType(ScaleType.MATRIX);
      } else {
        mMode = MODE_UNABLE;
      }
    }
    private float distance(MotionEvent event) {
      float dx = event.getX(1) - event.getX(0);
      float dy = event.getY(1) - event.getY(0);
      return (float) Math.sqrt(dx * dx + dy * dy);
    }
    public void onDoubleClick() {
      float scale = isZoomChanged() ? 1 : DOUBLE_CLICK_SACLE;
      mCurrentMatrix.set(mMatrix);
      mCurrentMatrix.postScale(scale, scale, getWidth() / 2,
          getHeight() / 2);
      setImageMatrix(mCurrentMatrix);
    }
  }
  private class GestureListener extends SimpleOnGestureListener {
    private final MatrixTouchListener mTouchListener;
    public GestureListener(MatrixTouchListener listener) {
      this.mTouchListener = listener;
    }
    @Override
    public boolean onDown(MotionEvent e) {
      return true;
    }
    @Override
    public boolean onDoubleTap(MotionEvent e) {
      mTouchListener.onDoubleClick();
      return true;
    }
    @Override
    public boolean onSingleTapUp(MotionEvent e) {
      return super.onSingleTapUp(e);
    }
    @Override
    public void onLongPress(MotionEvent e) {
      super.onLongPress(e);
    }
    @Override
    public boolean onScroll(MotionEvent e1, MotionEvent e2,
        float distanceX, float distanceY) {
      return super.onScroll(e1, e2, distanceX, distanceY);
    }
    @Override
    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
        float velocityY) {
      return super.onFling(e1, e2, velocityX, velocityY);
    }
    @Override
    public void onShowPress(MotionEvent e) {
      super.onShowPress(e);
    }
    @Override
    public boolean onDoubleTapEvent(MotionEvent e) {
      return super.onDoubleTapEvent(e);
    }
    @Override
    public boolean onSingleTapConfirmed(MotionEvent e) {
      if (mSingleTapListener != null)
        mSingleTapListener.onSingleTap(e);
      return super.onSingleTapConfirmed(e);
    }
  }
  public interface OnMovingListener {
    public void startDrag();
    public void stopDrag();
  }
  public interface OnSingleTapListener {
    public void onSingleTap(MotionEvent e);
  }
}

我对其中定义OnSingleTapListener接口的方法稍作了一些修改，为onSingleTap回调方法增加了MotionEvent类型的参数，来方便我们根据用户具体的事件内容作出对应的控制。

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