android开发之多点触摸(multitouch)

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 = new Paint();

touchPaints.setColor(colors);

}

}

/*

* 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, 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, 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));

}

}