Android 单指触控拖拽，两指触控缩放

 import android.app.Activity;

 import android.os.Bundle;

 import android.util.Log;

 import android.view.MotionEvent;

 import android.view.View;

 import android.view.Window;

 import android.widget.FrameLayout;

 import android.widget.FrameLayout.LayoutParams;

 public class MainActivity extends Activity {

     View view;

     public static final int DRAG = 1;

     public static final int SCALE = 2;

     int mode = 1;

     float lengthOld = 1;//初始化两指之间原长

     //初始化圆点高宽,java代码中操作的宽高都是像素值，dp*density转成px

     int width = 40;

     int height = 40;

     @Override

     protected void onCreate(Bundle savedInstanceState) {

         super.onCreate(savedInstanceState);

         requestWindowFeature(Window.FEATURE_NO_TITLE);

         setContentView(R.layout.activity_main);

         Log.e("TAG", "像素密度："+getResources().getDisplayMetrics().density);

         view = findViewById(R.id.view);

     }

     /**

      * 在MainActivity中画一个圆

      * Activity重写onTouchEvent，触摸监听

      * getRawX(),getRawY()是获取手机屏幕上的点到屏幕左上角顶点的距离

      * getX(),getY()是获取视图坐标，子视图在父视图中的位置

      */

     @Override

     public boolean onTouchEvent(MotionEvent event) {

         //记录坐标，圆点距离视图顶点

         int x = (int) event.getX();

         int y = (int) event.getY();

         //多指触控

         //获取事件源，并通过event.getActionMasked()加入多点触控支持

         switch (event.getAction() & event.getActionMasked()) {

         case MotionEvent.ACTION_DOWN:

             //单指移动

             mode = DRAG;

             break;

         case MotionEvent.ACTION_POINTER_DOWN:

             //多指缩放

             Log.e("TAG", "多指移动");

             mode = SCALE;

             //计算两指间开始的原长

             lengthOld = calculation(event);

             break;

         case MotionEvent.ACTION_UP:

             lengthOld = 1;//复位

             break;

         case MotionEvent.ACTION_MOVE:

             if(mode == DRAG){

                 //单指，直接设置坐标

                 FrameLayout.LayoutParams params = new FrameLayout.LayoutParams(width, height);

                 params.setMargins(x, y, 0, 0);

                 view.setLayoutParams(params);

             }else{

                 //两指缩放，要计算缩放比例

                 float scale = calculation(event) / lengthOld;

                 width = (int) (view.getWidth() * scale);

                 height = (int) (view.getHeight() * scale);

                 FrameLayout.LayoutParams params = (LayoutParams) view.getLayoutParams();

                 params.width = width;

                 params.height = height;

                 view.setLayoutParams(params);

             }

             break;

         }

         return true;

     }

     private float calculation(MotionEvent event) {

         float x1 = event.getX();

         float x2 = event.getX(1);

         float y1 = event.getY();

         float y2 = event.getY(1);

         return (float) Math.sqrt(Math.pow((x1-x2), 2)+Math.pow((y1-y2), 2));

     }

 }

xml中设置

 <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"

     android:layout_width="match_parent"

     android:layout_height="match_parent" >

     <View

         android:id="@+id/view"

         android:layout_width="20dp"

         android:layout_height="20dp"

         android:background="@drawable/oval" />

 </FrameLayout>