Android通过手势实现的缩放处理

最新推荐文章于 2025-08-20 18:34:09 发布

ljbal

最新推荐文章于 2025-08-20 18:34:09 发布

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分类专栏： Android 文章标签：移动开发

本文链接：https://blog.youkuaiyun.com/ljbal/article/details/84022600

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本活动展示了如何在触摸屏设备上实现多点触摸交互，并通过编程绘制响应于触摸动作的图形，涉及Canvas、MotionEvent等核心API的应用。

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01 import android.app.Activity; 

02
import android.content.Context; 

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import android.graphics.Canvas; 

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import android.graphics.Color; 

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import android.graphics.Paint; 

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import android.os.Bundle; 

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import android.util.DisplayMetrics; 

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import android.view.MotionEvent; 

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import android.view.View; 

10
  

11/** 

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 * ... 

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 *  

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 * @author vlinux 

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 *  

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 */

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public class MultiTouchTestActivity extends Activity { 

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    /** Called when the activity is first created. */

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    @Override

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    public void onCreate(Bundle savedInstanceState) { 

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        super.onCreate(savedInstanceState); 

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        // setContentView(R.layout.main); 

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        View view = new MultiTouchView(this); 

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        setContentView(view); 

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    } 

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    class MultiTouchView extends View { 

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        private float x1; 

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        private float y1; 

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        private float x2; 

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        private float y2; 

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        public MultiTouchView(Context context) { 

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            super(context); 

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            // TODO Auto-generated constructor stub 

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        } 

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        @Override

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        public boolean onTouchEvent(MotionEvent event) { 

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            // TODO Auto-generated method stub 

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            float size = event.getSize(); 

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            int szi = (int) size; 

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            int dxi = szi >> 12; 

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            int dyit = ((1 << 12) - 1); 

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            int dyi = szi & dyit; 

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            DisplayMetrics metrics = getResources().getDisplayMetrics(); 

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            float dx = metrics.widthPixels * dxi / (float) dyit; 

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            float dy = metrics.heightPixels * dyi / (float) dyit; 

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            x1 = event.getX(); 

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            y1 = event.getY(); 

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            x2 = x1 + dx; 

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            y2 = y1 + dy; 

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            invalidate(); 

61
  

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            return true; 

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        } 

64
  

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        @Override

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        protected void onDraw(Canvas canvas) { 

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            // TODO Auto-generated method stub 

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            super.onDraw(canvas); 

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            float r = (float) Math.sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) 

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                    * (y1 - y2)) / 2; 

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            r = 50 >= r ? 50 : r; 

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            Paint paint = new Paint(); 

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            paint.setColor(Color.BLUE); 

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            canvas.drawCircle(x1, y1, r, paint); 

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        } 

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    } 

81
  

82}