实现图片的点击拖动与多指放大缩小

实现图片的点击拖动与多指放大缩小

public class MainActivity extends AppCompatActivity {

PhoteView需要导入依赖：

   compile'com.github.chrisbanes.photoview:library:+'

  private PhotoView photoView;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
     super.onCreate(savedInstanceState);
     setContentView(R.layout.activity_main);
     photoView = (PhotoView) findViewById(R.id.photo_view);
  }

  /**
   * 事件分发的方法 ,需要activty把事件传给photoview ,photoview才能接受到我们的触摸事件
   */
  @Override
  public boolean dispatchTouchEvent(MotionEvent ev) {

    //activity接受到事件分发之后,我们手动处理触摸事件,只给传给我们自己的onTouchEvent方法;
     onTouchEvent(ev);
     return true;
  }

    //手指按下的坐标
    float downX;
    float downY;

    //手指移动前的坐标
    float lastX;
    float lastY;
    boolean moveble = false;
    boolean isMorePoint = false;

    @Override
    public boolean onTouchEvent(MotionEvent event) {
      super.onTouchEvent(event);

      //接受多指触控需要用 event.getAction() & MotionEvent.ACTION_MASK 来获得当前的触摸事件
      switch (event.getAction() & MotionEvent.ACTION_MASK) {
          case MotionEvent.ACTION_DOWN:
              downX = event.getX();
              downY = event.getY();
              lastX = downX;
              lastY = downY;

              if (downX > photoView.getX()
                && downX < photoView.getX() + photoView.getWidth()
                && downY > photoView.getY()
                && downY < photoView.getY() + photoView.getHeight()
                ) {
               moveble = true;
              } else {
               moveble = false;
              }
              break;
          case MotionEvent.ACTION_MOVE:

              //当前手指摸出的坐标
              float currentX = event.getX();
              float currentY = event.getY();

              //我手指移动的距离
              float gapX = currentX - lastX;
              float gapY = currentY - lastY;

              //  如果点击位置不在图片上的话不做任何逻辑处理  moveble ==true 的时候做处理
              if (moveble) {
               if (isMorePoint) {
                //多指的时候 把事件交给photoview去处理,它自己会根据事件去做放大缩小的逻辑 ,
                photoView.dispatchTouchEvent(event);
                } else {
                //单指的时候拖拽的逻辑设置图片新的位置==原来的位置 + 手指移动的距离
                photoView.setX(photoView.getX() + gapX);
                photoView.setY(photoView.getY() + gapY);
                }
              }
              lastX = event.getX();
              lastY = event.getY();
              break;
          case MotionEvent.ACTION_UP:

              break;

          //除了第一个手指之外别的手指按下时触发
          case MotionEvent.ACTION_POINTER_DOWN:
              isMorePoint = true;
              break;
          //除了第一个手指之外别的手指抬起时触发
          case MotionEvent.ACTION_POINTER_UP:
              isMorePoint = false;
              break;
      }

      return true;
   }
}

XML布局

    android:id="@+id/ll"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

            android:src="@drawable/brad_pitt"//自行添加图片
        android:id="@+id/photo_view"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />