android 基于surfaceview 的多点触控实现
? ? ? ?hello，各位朋友。最近接到一个功能需要实现多点触控，也就是我们通常所看到的把手指放在屏幕上，可以放大和缩小图片的 操作。在google上查找了一些资料，发现很多都是使用imageView在实现的。但是在游戏的开发过程中，使用surfaceview效率会更高一些，所以就尝试使用surfaceview来实现。
看代码：
public class DisplayActivity extends Activity {private SurfaceView videoView;private SurfaceHolder sfh;private Canvas canvas;private Paint paint;private boolean flag = true;private int screenW, screenH;private Bitmap bmpIcon;//记录两个触屏点的坐标private int x1, x2, y1, y2;//倍率private float rate = 1;//记录上次的????private float oldRate = 1;//记录第一次触屏时线段的长??private float oldLineDistance;//判定是否头次多指触点屏幕private boolean isFirst = true;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.media_play);videoView = (SurfaceView)findViewById(R.id.videoView);sfh = videoView.getHolder();sfh.addCallback(new DisplaySurfaceView());DisplayMetrics dm = new DisplayMetrics(); getWindowManager().getDefaultDisplay().getMetrics(dm); screenW = dm.widthPixels; screenH = (dm.heightPixels)/2;}class DisplaySurfaceView implements SurfaceHolder.Callback{@Overridepublic void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {}@Overridepublic void surfaceCreated(SurfaceHolder arg0) {new ImageThread().start();}@Overridepublic void surfaceDestroyed(SurfaceHolder arg0) {flag = false;}}@Overridepublic boolean onTouchEvent(MotionEvent event) {if (event.getAction() == MotionEvent.ACTION_UP) {isFirst = true;oldRate = rate;} else {if (event.getPointerCount() > 1) { x1 = (int) event.getX(0);y1 = (int) event.getY(0);x2 = (int) event.getX(1);y2 = (int) event.getY(1);if (event.getPointerCount() == 2) {if (isFirst) {//得到第一次触屏时线段的长??oldLineDistance = (float) Math.sqrt(Math.pow(event.getX(1) - event.getX(0), 2) + Math.pow(event.getY(1) - event.getY(0), 2));isFirst = false;} else {//得到非第????触屏时线段的长度float newLineDistance = (float) Math.sqrt(Math.pow(event.getX(1) - event.getX(0), 2) + Math.pow(event.getY(1) - event.getY(0), 2));//获取本次的缩放比??rate = oldRate * newLineDistance / oldLineDistance;}}}}return true;}@Overridepublic boolean onKeyDown(int keyCode, KeyEvent event) {return super.onKeyDown(keyCode, event);}class ImageThread extends Thread{@Overridepublic void run() {while (flag) {long start = System.currentTimeMillis();myDraw();long end = System.currentTimeMillis();try {if (end - start < 50) {Thread.sleep(50 - (end - start));}} catch (InterruptedException e) {e.printStackTrace();}}}}public void myDraw() {try {canvas = sfh.lockCanvas();if (canvas != null) {canvas.drawColor(Color.BLACK);canvas.save();//缩放画布(以图片中心点进行缩放，XY轴缩放比例相??bmpIcon = BitmapFactory.decodeResource(this.getResources(), R.drawable.aa);canvas.scale(rate, rate, screenW / 2, screenH / 2);int width = screenW / 2 - bmpIcon.getWidth() / 2;int height = screenH / 2 - bmpIcon.getHeight() / 2;//绘制位图iconcanvas.drawBitmap(bmpIcon, width, height, paint);canvas.restore();//便于观察，这里绘制两个触点时形成的线??//canvas.drawLine(x1, y1, x2, y2, paint);sfh.unlockCanvasAndPost(canvas);}} catch (Exception e) {e.printStackTrace();} finally {}}@Overridepublic void onConfigurationChanged(Configuration newConfig) {super.onConfigurationChanged(newConfig);}}?media_play.xml
<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" > <TextView android:id="@+id/displayName" android:layout_width="wrap_content" android:layout_height="wrap_content" android:gravity="left" android:text="321321321" android:textColor="#AA1122" /> <LinearLayout android:layout_width="fill_parent" android:layout_height="400dp" > <SurfaceView android:id="@+id/videoView" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_gravity="center" android:scaleType="matrix" /> </LinearLayout> <Button android:id="@+id/aaaBtn" android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="123321" /></LinearLayout>?这样就实现了多点触控，放大和缩小图片的效果了，aa这个图片是自己随便找的一个，可以根据实际情况修改。