Android通过手势实现的缩放处理

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);

}

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