自定义View(多点触控)

XML布局

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    tools:context=".MainActivity" >    <ImageView        android:id="@+id/image"        android:layout_width="wrap_content"        android:layout_height="wrap_content" /></RelativeLayout>

MainActivity中

package com.example.day04_touch;import android.os.Bundle;import android.app.Activity;import android.content.Context;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Matrix;import android.graphics.Paint;import android.util.AttributeSet;import android.util.DisplayMetrics;import android.view.Menu;import android.view.MotionEvent;import android.view.SurfaceHolder;import android.view.SurfaceView;public class MainActivity extends Activity {    SurfaceHolder holder;    private int width;    private int height;    private Bitmap bitmap;    private int imageW;    private int imageH;    private int x;    private int y;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(new MySurface(this));        // 获取屏幕的宽和高 DisplayMetrics类专门获取像素值        DisplayMetrics metrics = new DisplayMetrics();        getWindowManager().getDefaultDisplay().getMetrics(metrics);        width = metrics.widthPixels; // 屏幕的宽度(像素值)        height = metrics.heightPixels; // 屏幕的高度(像素值)        bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.a);        // 得到图片的宽高        imageW = bitmap.getWidth();        imageH = bitmap.getHeight();        // 设置图片的位置        x = (width - imageW) / 2;        y = (height - imageH) / 2;    }    // 绘制图片    public void setimage(float scale, int bwidth, int bheight) {        // 得到画布        Canvas canvas = holder.lockCanvas();        // 设置画布的颜色        canvas.drawColor(Color.BLACK);        // 设置画笔        Paint paint = new Paint();        // 画矩形        canvas.drawRect(0, 0, bwidth, bheight, paint);        // 得到Matrix类 用于控制图片的缩放        Matrix matrix = new Matrix();        // 设置缩放比例        matrix.postScale(scale, scale);        // 得到缩放后的bitmap图片        Bitmap bafter = Bitmap.createBitmap(bitmap, 0, 0, bwidth, bheight,                matrix, true);        // 得到新的bitmap的宽度和高度并且重新计算位置        imageW = bafter.getWidth();        imageH = bafter.getHeight();        // 重新计算图片的位置        x = (bwidth - imageW) / 2;        y = (bheight - imageH) / 2;        // 平移过去        canvas.translate(x, y);        // 重新绘制bitmap        canvas.drawBitmap(bitmap, matrix, paint);        // 解锁,把画布显示到屏幕上        holder.unlockCanvasAndPost(canvas);    }    @Override    public boolean onTouchEvent(MotionEvent event) {        // 获得触控点个数        int pointerCount = event.getPointerCount();        if (pointerCount == 2) {            // 获取两个点的距离            float pointA = event.getX(0);            float pointB = event.getX(1);            // 判断哪个大            // 如果第一个点小于第二个点就调换位置            if (pointA < pointB) {                float t = pointA;                pointA = pointB;                pointB = t;            }            // 只要手指不抬起，就进行缩放            if (!(event.getAction() == MotionEvent.ACTION_UP)) {                float scale = getScale(pointA, pointB) / 3;                setimage(scale, bitmap.getWidth(), bitmap.getHeight());            }        }        return super.onTouchEvent(event);    }    // 缩放比    public float getScale(float pointA, float pointB) {        // 缩放比例        float scale = pointA / pointB;        return scale;    }    class MySurface extends SurfaceView implements SurfaceHolder.Callback {        public MySurface(Context context) {            super(context);            // 获得SurfaceHolder对象            holder = getHolder();            // 为SurfaceView添加状态监听            holder.addCallback(this);            // 设置焦点            setFocusable(true);        }        @Override        public void surfaceChanged(SurfaceHolder holder, int format, int width,                int height) {            // TODO Auto-generated method stub        }        @Override        public void surfaceCreated(SurfaceHolder holder) {            // TODO Auto-generated method stub            setimage(1.0f, bitmap.getWidth(), bitmap.getHeight());        }        @Override        public void surfaceDestroyed(SurfaceHolder holder) {            // TODO Auto-generated method stub        }    }}