Android通過手勢實現的縮放處理

import android.app.Activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.os.Bundle;
import android.util.DisplayMetrics;
import android.view.MotionEvent;
import android.view.View;

/**

...

@author vlinux
/
public class MultiTouchTestActivity extends Activity {
 /** Called when the activity is first created. /
 @Override
 public void onCreate(Bundle savedInstanceState) {

 super.onCreate(savedInstanceState);
 // setContentView(R.layout.main);
 View view = new MultiTouchView(this);
 setContentView(view);

}
class MultiTouchView extends View {

 private float x1;
 private float y1;
 private float x2;
 private float y2;

 public MultiTouchView(Context context) {
     super(context);
     // TODO Auto-generated constructor stub
 }

 @Override
 public boolean onTouchEvent(MotionEvent event) {
     // TODO Auto-generated method stub

     float size = event.getSize();

     int szi = (int) size;
     int dxi = szi >> 12;
     int dyit = ((1 << 12) - 1);
     int dyi = szi & dyit;

     DisplayMetrics metrics = getResources().getDisplayMetrics();
     float dx = metrics.widthPixels * dxi / (float) dyit;
     float dy = metrics.heightPixels * dyi / (float) dyit;

     x1 = event.getX();
     y1 = event.getY();

     x2 = x1 + dx;
     y2 = y1 + dy;

     invalidate();

     return true;
 }

 @Override
 protected void onDraw(Canvas canvas) {
     // TODO Auto-generated method stub
     super.onDraw(canvas);

     float r = (float) Math.sqrt((x1 - x2) * (x1 - x2) + (y1 - y2)
             * (y1 - y2)) / 2;
     r = 50 >= r ? 50 : r;

     Paint paint = new Paint();
     paint.setColor(Color.BLUE);
     canvas.drawCircle(x1, y1, r, paint);

 }


}


}</pre>