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Android多点触控MultiTouch浅析


申明:

 

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
	 */
	@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 {
				// 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,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) {
			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:

\


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1
				if (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

www.bkjia.comtruehttp://www.bkjia.com/Androidjc/1003388.htmlTechArticleAndroid多点触控MultiTouch浅析 申明: 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...

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