Android开发中实现多点触控的方法

其实，Android应用程序开发中，多点触摸（Multitouch）不是那么遥不可及，实现起来也很简单。如果您对开发多点触摸程序感兴趣的话，那么本文将是一个很好的开始，本例只需要两个类就能实现多点触摸。

首先来看看我们的视图类MTView.java:

package com.ideasandroid.demo;  
    
import android.content.Context;  
import android.graphics.Canvas;  
import android.graphics.Color;  
import android.graphics.Paint;  
import android.view.MotionEvent;  
import android.view.SurfaceHolder;  
import android.view.SurfaceView;  
    
public class MTView extends SurfaceView implements SurfaceHolder.Callback {  
    
    private static final int MAX_TOUCHPOINTS = 10;  
    private static final String START_TEXT = "请随便触摸屏幕进行测试";  
    private Paint textPaint = new Paint();  
    private Paint touchPaints\[\] = new Paint\[MAX_TOUCHPOINTS\];  
    private int colors\[\] = new int\[MAX_TOUCHPOINTS\];  
    
    private int width, height;  
    private float scale = 1.0f;  
    
    public MTView(Context context) {  
        super(context);  
        SurfaceHolder holder = getHolder();  
        holder.addCallback(this);  
        setFocusable(true); // 确保我们的View能获得输入焦点  
        setFocusableInTouchMode(true); // 确保能接收到触屏事件  
        init();  
    }  
    
    private void init() {  
        // 初始化10个不同颜色的画笔  
        textPaint.setColor(Color.WHITE);  
        colors\[0\] = Color.BLUE;  
        colors\[1\] = Color.RED;  
        colors\[2\] = Color.GREEN;  
        colors\[3\] = Color.YELLOW;  
        colors\[4\] = Color.CYAN;  
        colors\[5\] = Color.MAGENTA;  
        colors\[6\] = Color.DKGRAY;  
        colors\[7\] = Color.WHITE;  
        colors\[8\] = Color.LTGRAY;  
        colors\[9\] = Color.GRAY;  
        for (int i = 0; i < MAX_TOUCHPOINTS; i++) {  
            touchPaints\[i\] = new Paint();  
            touchPaints\[i\].setColor(colors\[i\]);  
        }  
    }  
    
    /*  
     * 处理触屏事件  
     */ 
    @Override  
    public boolean onTouchEvent(MotionEvent event) {  
        // 获得屏幕触点数量  
        int pointerCount = event.getPointerCount();  
        if (pointerCount > MAX_TOUCHPOINTS) {  
            pointerCount = MAX_TOUCHPOINTS;  
        }  
        // 锁定Canvas,开始进行相应的界面处理  
        Canvas c = getHolder().lockCanvas();  
        if (c != null) {  
            c.drawColor(Color.BLACK);  
            if (event.getAction() == MotionEvent.ACTION_UP) {  
                // 当手离开屏幕时，清屏  
            } else {  
                // 先在屏幕上画一个十字，然后画一个圆  
                for (int i = 0; i < pointerCount; i++) {  
                    // 获取一个触点的坐标，然后开始绘制  
                    int id = event.getPointerId(i);  
                    int x = (int) event.getX(i);  
                    int y = (int) event.getY(i);  
                    drawCrosshairsAndText(x, y, touchPaints\[id\], i, id, c);  
                }  
                for (int i = 0; i < pointerCount; i++) {  
                    int id = event.getPointerId(i);  
                    int x = (int) event.getX(i);  
                    int y = (int) event.getY(i);  
                    drawCircle(x, y, touchPaints\[id\], c);  
                }  
            }  
            // 画完后，unlock  
            getHolder().unlockCanvasAndPost(c);  
        }  
        return true;  
    }  
    
    /**  
     * 画十字及坐标信息  
     *  
     * @param x  
     * @param y  
     * @param paint  
     * @param ptr  
     * @param id  
     * @param c  
     */ 
    private void drawCrosshairsAndText(int x, int y, Paint paint, int ptr,  
            int id, Canvas c) {  
        c.drawLine(0, y, width, y, paint);  
        c.drawLine(x, 0, x, height, paint);  
        int textY = (int) ((15 + 20 * ptr) * scale);  
        c.drawText("x" + ptr + "=" + x, 10 * scale, textY, textPaint);  
        c.drawText("y" + ptr + "=" + y, 70 * scale, textY, textPaint);  
        c.drawText("id" + ptr + "=" + id, width - 55 * scale, textY, textPaint);  
    }  
    
    /**  
     * 画圆  
     *  
     * @param x  
     * @param y  
     * @param paint  
     * @param c  
     */ 
    private void drawCircle(int x, int y, Paint paint, Canvas c) {  
        c.drawCircle(x, y, 40 * scale, paint);  
    }  
    
    /*  
     * 进入程序时背景画成黑色，然后把“START_TEXT”写到屏幕  
     */ 
    public void surfaceChanged(SurfaceHolder holder, int format, intwidth,  
            int height) {  
        this.width = width;  
        this.height = height;  
        if (width > height) {  
            this.scale = width / 480f;  
        } else {  
            this.scale = height / 480f;  
        }  
        textPaint.setTextSize(14 * scale);  
        Canvas c = getHolder().lockCanvas();  
        if (c != null) {  
            // 背景黑色  
            c.drawColor(Color.BLACK);  
            float tWidth = textPaint.measureText(START_TEXT);  
            c.drawText(START_TEXT, width / 2 - tWidth / 2, height / 2,  
                    textPaint);  
            getHolder().unlockCanvasAndPost(c);  
        }  
    }  
    
    public void surfaceCreated(SurfaceHolder holder) {  
    }  
    
    public void surfaceDestroyed(SurfaceHolder holder) {  
    }  
    
}

接下来看看我们的Activity，MultitouchVisible.java

package com.ideasandroid.demo;  
    
import android.app.Activity;  
import android.os.Bundle;  
import android.view.Window;  
import android.view.WindowManager;  
    
public class MultitouchVisible extends Activity {  
    @Override  
    public void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        //隐藏标题栏  
        requestWindowFeature(Window.FEATURE_NO_TITLE);  
        //设置成全屏  
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,  
                WindowManager.LayoutParams.FLAG_FULLSCREEN);  
        //设置为上面的MTView  
        setContentView(new MTView(this));  
    }  
}

希望本文对您有所帮助。