Android多点触摸交互处理-图片缩放

创建一个新工程LearnMultipointTouich一个空的Activity，方式一个ImageView和一个Checkbox控件 实现目标：如果Checkbox打勾这移动图片；否则缩放图片。 实现原理：1、根据event.getPointerCount获取手机上触摸点个数 2：两个触摸点之间的距离  利用勾股定理可以算出两个触摸点之间的距离 3：onTouch事件的返回时差异：默认是false，即处理第一个事件后，后续事件不处理，如果要触发后续事件应该return true

MainActivity.java代码

public class MainActivity extends AppCompatActivity {     private LinearLayout root;     private CheckBox cbMove;     ImageView iv;     //两个点之间的x坐标差的平方+y坐标差的平方 然后求其平方根即时两个点之间的距离     float lastCurrentDistance=-1;//两个触摸点之间的最后距离     @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_main);         cbMove= (CheckBox) findViewById(R.id.cbMove);         iv= (ImageView) findViewById(R.id.imageView);         root= (LinearLayout) findViewById(R.id.fmContainer);         root.setOnTouchListener(new View.OnTouchListener() {             @Override             public boolean onTouch(View v, MotionEvent event) {                 switch (event.getAction()){  //通过event判断此时的触摸类型                     case MotionEvent.ACTION_DOWN://触摸按下事件                         break;                     case MotionEvent.ACTION_MOVE://触摸移动事件                         if (cbMove.isChecked()==true){                             goMoveImg(v,event);                         }else{                             goBlowUpShrinkImg(v, event);                         }                         break;                     case MotionEvent.ACTION_UP://触摸弹起事件                     default:                         break;                 }                 return true;  //默认是false，即处理第一个事件后，后续事件不处理，如果要触发后续事件应该return true             }         });     }     private void goBlowUpShrinkImg(View v, MotionEvent event) {         float currentDistance;//两个触摸点之间的距离  利用勾股定理可以算出两个触摸点之间的距离         if (event.getPointerCount()>=2){  ////获取触摸点的个数据说最多可以获取10个触摸点             float offsetX=event.getX(0)-event.getX(1);             float offsetY=event.getY(0)-event.getY(1);             currentDistance= (float) Math.sqrt(offsetX*offsetX+offsetY*offsetY);             if (lastCurrentDistance<0){                 lastCurrentDistance=currentDistance;             } else{                 //由于android的手指触摸会存在偏差，我们取值为8进行判断放大或缩小操作                 if (currentDistance-lastCurrentDistance>8){                     System.out.println("放大操作");                     LinearLayout.LayoutParams lp= (LinearLayout.LayoutParams) iv.getLayoutParams();                     lp.width= (int) (1.1f*iv.getWidth());                     lp.height= (int) (1.1f*iv.getHeight());                     iv.setLayoutParams(lp);                     lastCurrentDistance=currentDistance;                 }else if (lastCurrentDistance-currentDistance>8){                     System.out.println("缩小操作");                     LinearLayout.LayoutParams lp= (LinearLayout.LayoutParams) iv.getLayoutParams();                     lp.width= (int) (0.9f*iv.getWidth());                     lp.height= (int) (0.9f*iv.getHeight());                     iv.setLayoutParams(lp);                     lastCurrentDistance=currentDistance;                 }             }         }     }     private void goMoveImg(View v, MotionEvent event) {         //获取触摸点坐标         System.out.println(String.format("触摸点坐标x:%f,y:%f",event.getX(),event.getY()));         LinearLayout.LayoutParams lp= (LinearLayout.LayoutParams) iv.getLayoutParams();         lp.leftMargin= (int) event.getX();         lp.topMargin= (int) event.getY();         iv.setLayoutParams(lp);  //重新设置图片的左上角坐标为触摸坐标     } }