Android开发之多点触摸（Multitouch）

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，android应用程序开发中，多点触摸不是那么遥不可及，实现起来也很简单，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, int width,
			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) {
	}

}

代码中都做了相应的注释，这里就不多说。

        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));
    }
}

Android : 多点触摸（1，2，3）
http://blog.csdn.net/tsiannian/article/details/6636463
http://blog.csdn.net/tsiannian/article/details/6636480
http://blog.csdn.net/tsiannian/article/details/6638929

Muilti-touch 双指缩放的实现探索
http://blog.csdn.net/barryhappy/article/details/7392326