Android多點觸控MultiTouch淺析

Android多點觸控MultiTouch淺析
申明：

 

下面實現如何通過應用程式層支援多點觸控操作，對於常規的控制項觸控操實現onTouchEvent()方法來處理。同時對onTouchEvent方法的參數MotionEvent進行一些瞭解。

 

本文：

下面會用兩個應用樣本來初步學習一下Android中的多點觸控。

 

樣本一（DemoMultiTouch-Canvas）：核心技術介紹

本樣本是在SurfaceView中利用Canvas來展示使用者的多點觸控，不過核心技術還是一個常見的方法：onTouchEvent(MotionEvent event)

MotionEvent有以下幾個方法需要大家注意一下，不過了是一些常見的方法，如果你onTouchEvent使用得多的話。

event.getAction() // 擷取觸控動作比如ACTION_DOWN
event.getPointerCount(); // 擷取觸控點的數量，比如2則可能是兩個手指同時按壓螢幕
event.getPointerId(nID); // 對於每個觸控的點的細節，我們可以通過一個迴圈執行getPointerId方法擷取索引
event.getX(nID); // 擷取第nID個觸控點的x位置
event.getY(nID); // 擷取第nID個點觸控的y位置
event.getPressure(nID); // LCD可以感應出使用者的手指壓力，當然具體的層級由驅動和物理硬體決定的
event.getDownTime() // 按下開始時間
event.getEventTime() // 事件結束時間
event.getEventTime()-event.getDownTime()); // 總共按下時花費時間

 

代碼展示：

 

public class MTView extends SurfaceView implements SurfaceHolder.Callback {private static final int MAX_TOUCHPOINTS = 10;private static final String START_TEXT = "請隨便觸控螢幕幕進行測試";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); // 確保我們的View能獲得輸入焦點setFocusableInTouchMode(true); // 確保能接收到觸屏事件init();}private void init() {// 初始化10個不同顏色的畫筆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]);}}/** * 處理觸屏事件 */@Overridepublic boolean onTouchEvent(MotionEvent event) {// 獲得螢幕觸點數量int pointerCount = event.getPointerCount();if (pointerCount > MAX_TOUCHPOINTS) {pointerCount = MAX_TOUCHPOINTS;}// 鎖定Canvas,開始進行相應的介面處理Canvas c = getHolder().lockCanvas();if (c != null) {c.drawColor(Color.BLACK);if (event.getAction() == MotionEvent.ACTION_UP) {// 當手離開螢幕時，清屏} else {// 在每一個觸點上繪製一個十字和座標資訊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);}// 在每一個觸點上繪製一個圓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);}}// 畫完後，unlockgetHolder().unlockCanvasAndPost(c);}return true;}/** * 畫十字及座標資訊 *  * @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);}/** * 畫圓 *  * @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);}/** * 進入程式時背景畫成黑色，然後把START_TEXT寫到螢幕 */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));

 

 

運行：

樣本二（DemoMultiTouch-ImageView）：

通過多點觸屏放大或縮小映像 beforeLenght用來儲存前一時間兩點之間的距離 afterLenght用來儲存目前時間兩點之間的距離

 

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:// 得到兩個點之間的長度afterLenght = (float) Math.sqrt((moveX * moveX)+ (moveY * moveY));float gapLenght = afterLenght - beforeLenght;if (gapLenght == 0) {break;}// 如果目前時間兩點距離大於前一時間兩點距離，則傳0，否則傳1if (gapLenght > 0) {this.setScale(scale, 0);} else {this.setScale(scale, 1);}beforeLenght = afterLenght;break;}}}

 

 

讓圖片跟隨手指觸屏的位置移動 beforeX、Y是用來儲存前一位置的座標 afterX、Y是用來儲存當前位置的座標。它們的差值就是ImageView各座標的增加或減少值。

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;}}

 

用來放大縮小ImageView 因為圖片是填充ImageView的，所以也就有放大縮小圖片的效果 flag為0是放大圖片，為1是縮小圖片

 

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事件則如下：

 

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;}

 

源碼下載：

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