申明：

参考：http://www.jcodecraeer.com/a/anzhuokaifa/androidkaifa/2013/0226/914.html

下面实现如何通过应用层支持多点触控操作，对于常规的控件触控操实现onTouchEvent()方法来处理。同时对onTouchEvent方法的参数MotionEvent进行一些了解。

正文：

下面会用两个应用示例来初步学习一下Android中的多点触控。

示例一（DemoMultiTouch-Canvas）：

核心技术介绍

本示例是在SurfaceView中利用Canvas来展示用户的多点触控，不过核心技术还是一个常见的方法：onTouchEvent(MotionEvent event)

MotionEvent有以下几个方法需要大家注意一下，不过了是一些常见的方法，如果你onTouchEvent使用得多的话。

event.getAction() // 获取触控动作比如ACTION_DOWN
event.getPointerCount(); // 获取触控点的数量，比如2则可能是两个手指同时按压屏幕
event.getPointerId(nID); // 对于每个触控的点的细节，我们可以通过一个循环执行getPointerId方法获取索引
event.getX(nID); // 获取第nID个触控点的x位置
event.getY(nID); // 获取第nID个点触控的y位置
event.getPressure(nID); // LCD可以感应出用户的手指压力，当然具体的级别由驱动和物理硬件决定的
event.getDownTime() // 按下开始时间
event.getEventTime() // 事件结束时间
event.getEventTime()-event.getDownTime()); // 总共按下时花费时间

代码展示：

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 */@Overridepublic 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 {// 在每一个触点上绘制一个十字和坐标信息for (int i = 0; i < pointerCount; i++) {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);}// 在每一个触点上绘制一个圆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，unlockgetHolder().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) {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) {}}

使用上也是so easy：

setContentView(new MTView(this));

运行效果图：

Android多点触控MultiTouch浅析_第1张图片

示例二（DemoMultiTouch-ImageView）：

通过多点触屏放大或缩小图像 beforeLenght用来保存前一时间两点之间的距离 afterLenght用来保存当前时间两点之间的距离

public void scaleWithFinger(MotionEvent event) {float moveX = event.getX(1) - event.getX(0);float moveY = event.getY(1) - event.getY(0);switch (event.getAction()) {case MotionEvent.ACTION_DOWN:beforeLenght = (float) Math.sqrt((moveX * moveX)+ (moveY * moveY));break;case MotionEvent.ACTION_MOVE:// 得到两个点之间的长度afterLenght = (float) Math.sqrt((moveX * moveX)+ (moveY * moveY));float gapLenght = afterLenght - beforeLenght;if (gapLenght == 0) {break;}// 如果当前时间两点距离大于前一时间两点距离，则传0，否则传1if (gapLenght > 0) {this.setScale(scale, 0);} else {this.setScale(scale, 1);}beforeLenght = afterLenght;break;}}}

让图片跟随手指触屏的位置移动 beforeX、Y是用来保存前一位置的坐标 afterX、Y是用来保存当前位置的坐标。它们的差值就是ImageView各坐标的增加或减少值。

public void moveWithFinger(MotionEvent event) {switch (event.getAction()) {case MotionEvent.ACTION_DOWN:beforeX = event.getX();beforeY = event.getY();break;case MotionEvent.ACTION_MOVE:afterX = event.getX();afterY = event.getY();this.setLocation((int) (afterX - beforeX),(int) (afterY - beforeY));beforeX = afterX;beforeY = afterY;break;case MotionEvent.ACTION_UP:break;}}

用来放大缩小ImageView 因为图片是填充ImageView的，所以也就有放大缩小图片的效果 flag为0是放大图片，为1是缩小图片

private void setScale(float temp, int flag) {if (flag == 0) {this.setFrame(this.getLeft() - (int) (temp * this.getWidth()),this.getTop() - (int) (temp * this.getHeight()),this.getRight() + (int) (temp * this.getWidth()),this.getBottom() + (int) (temp * this.getHeight()));} else {this.setFrame(this.getLeft() + (int) (temp * this.getWidth()),this.getTop() + (int) (temp * this.getHeight()),this.getRight() - (int) (temp * this.getWidth()),this.getBottom() - (int) (temp * this.getHeight()));}}

onTouchEvent事件则如下：

public boolean onTouchEvent(MotionEvent event) {if (inView(imageView, event)) {if (event.getPointerCount() == 2) {imageView.scaleWithFinger(event);} else if (event.getPointerCount() == 1) {imageView.moveWithFinger(event);}}return true;}

源码下载：

http://download.csdn.net/detail/u013761665/8719349

Android多点触控MultiTouch浅析

申明：

正文：