Android开发中实现多点触摸的方法

推荐安卓开发神器（里面有各种UI特效和android代码库实例）

我们曾就《Android手势识别ViewFlipper触摸动画》做过详细的讲解，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,

        c.drawText("y" + ptr + "=" + y, 70 * scale, textY,

        c.drawText("id" + ptr + "=" + id, width - 55 * sc

    }  

   

    /**  

     * 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, i

            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

                    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));  

    }  

}