Android通过手势实现的缩放处理

     <pre class="brush:java; toolbar: true; auto-links: false;">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>    <br />