Android多点触控

可对图片进行缩放和移动 但是移动的只是内容图片，ImageView是固定的，自己定义的。

public class MainActivity extends Activity implements OnTouchListener {      // 放大缩小      Matrix matrix = new Matrix();      Matrix savedMatrix = new Matrix();         PointF start = new PointF();      PointF mid = new PointF();      float oldDist;         private ImageView myImageView;         // 模式      static final int NONE = 0;      static final int DRAG = 1;      static final int ZOOM = 2;      int mode = NONE;         @Override      public void onCreate(Bundle savedInstanceState) {          super.onCreate(savedInstanceState);          setContentView(R.layout.main);             myImageView = (ImageView) findViewById(R.id.iv_image);          myImageView.setOnTouchListener(this);         }         @Override      public boolean onTouch(View v, MotionEvent event) {          ImageView myImageView = (ImageView) v;          switch (event.getAction() & MotionEvent.ACTION_MASK) {          // 设置拖拉模式          case MotionEvent.ACTION_DOWN:              Log.i("point", "action_pointer_down");              matrix.set(myImageView.getImageMatrix());              savedMatrix.set(matrix);              start.set(event.getX(), event.getY());              mode = DRAG;              break;          case MotionEvent.ACTION_UP:          case MotionEvent.ACTION_POINTER_UP:              mode = NONE;              break;             // 设置多点触摸模式          case MotionEvent.ACTION_POINTER_DOWN:              oldDist = spacing(event);              if (oldDist > 10f) {                  savedMatrix.set(matrix);                  midPoint(mid, event);                  mode = ZOOM;              }              break;          // 若为DRAG模式，则点击移动图片          case MotionEvent.ACTION_MOVE:              if (mode == DRAG) {                  matrix.set(savedMatrix);                  matrix.postTranslate(event.getX() - start.x, event.getY() - start.y);              }              // 若为ZOOM模式，则点击触摸缩放              else if (mode == ZOOM) {                  float newDist = spacing(event);                  if (newDist > 10f) {                      matrix.set(savedMatrix);                      float scale = newDist / oldDist;                      // 设置硕放比例和图片的中点位置                      matrix.postScale(scale, scale, mid.x, mid.y);                  }              }              break;          }          myImageView.setImageMatrix(matrix);          return true;      }         // 计算移动距离      private float spacing(MotionEvent event) {          float x = event.getX(0) - event.getX(1);          float y = event.getY(0) - event.getY(1);          return FloatMath.sqrt(x * x + y * y);      }         // 计算中点位置      private void midPoint(PointF point, MotionEvent event) {          float x = event.getX(0) + event.getX(1);          float y = event.getY(0) + event.getY(1);          point.set(x / 2, y / 2);      }     }

<?xml version="1.0" encoding="utf-8"?>  <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"      android:layout_width="match_parent"      android:layout_height="match_parent"      android:orientation="vertical"       android:background="@android:color/black">         <ImageView          android:id="@+id/iv_image"          android:layout_width="wrap_content"          android:layout_height="wrap_content"          android:scaleType="matrix"          android:src="@drawable/koala" />     </LinearLayout>