多点触碰2

最新推荐文章于 2025-12-04 22:26:14 发布

最新推荐文章于 2025-12-04 22:26:14 发布 · 91 阅读

文章标签：

#移动开发

本文介绍了一款名为Pointer2Draw的应用程序，该程序能够通过正确处理多点触摸事件实现在屏幕上绘制的功能。文章详细解释了如何获取触摸点的数量、ID及坐标，并展示了如何使用Android提供的API来区分不同手指的动作。

前面写了一个Pointer2Draw的小程序。这个程序的神奇之处在于，你永远也别想绘制出任何东西。原因是根本没有所谓的0x00000107。下面看看如何正确的处理多点触摸，光靠event.getAction()吃饭的时代已经终结了……

(1)获得屏幕上的Pointer的数目：

view plain copy to clipboard print ?

intpointerCount=event.getPointerCount();

int pointerCount = event.getPointerCount(); 这个函数具体返回值受到物理设备的限制，我费了很大力气将十个手指放到了我的手机上，得到的结果仍然是8。

(2)得到手指的ID：Android提供了两个掩码方便我们操作ACTION_POINTER_ID_MASK 0x0000ff00,和ACTION_POINTER_ID_SHIFT 0x00000008。

view plain copy to clipboard print ?

if(pointerCount>1){
pointerId=(action&MotionEvent.ACTION_POINTER_ID_MASK)>>>
MotionEvent.ACTION_POINTER_ID_SHIFT;
}

if(pointerCount>1){ pointerId = (action & MotionEvent.ACTION_POINTER_ID_MASK)>>> MotionEvent.ACTION_POINTER_ID_SHIFT; } (3)利用ID获得坐标信息：

view plain copy to clipboard print ?

floatx=event.getX(pointerId);//获得第二个手指的坐标
floaty=event.getY(pointerId);

float x = event.getX(pointerId);//获得第二个手指的坐标 float y = event.getY(pointerId); 下面终于可以让Pointer2Draw运行起来了。

view plain copy to clipboard print ?

publicbooleanonTouchEvent(MotionEventevent){
intpointerCount=event.getPointerCount();
intpointerId=0;
intaction=event.getAction();
if(pointerCount>1){
pointerId=(action&MotionEvent.ACTION_POINTER_ID_MASK)>>>
MotionEvent.ACTION_POINTER_ID_SHIFT;
}
floatx=0;
floaty=0;
if(pointerId==1){
x=event.getX(pointerId);
y=event.getY(pointerId);
canvas.drawPoint(x,y,paint);
imgView.invalidate();
}
returntrue;
}

public boolean onTouchEvent(MotionEvent event){ int pointerCount = event.getPointerCount(); int pointerId = 0; int action = event.getAction(); if(pointerCount>1){ pointerId = (action & MotionEvent.ACTION_POINTER_ID_MASK)>>> MotionEvent.ACTION_POINTER_ID_SHIFT; } float x = 0; float y = 0; if(pointerId == 1){ x = event.getX(pointerId); y = event.getY(pointerId); canvas.drawPoint(x, y, paint); imgView.invalidate(); } return true; }

注意手指的ID是从0开始的，所以第二个手指的ID是1；然而遗憾的是程序只有在第二个手指DOWN和UP时才绘制。当第一个手指不动时，根本没有有效的方法对第二个手指的移动做出反应。然而触摸屏是很敏感的，你发现很难让它不产生ACTION_MOVE。我们利用Android提供的ACTION_MASK 0x000000ff来改善我们的代码：

view plain copy to clipboard print ?

publicclassPointer2DrawActivityextendsActivityimplementsOnTouchListener{
/**Calledwhentheactivityisfirstcreated.*/
ImageViewimgView;
Bitmapbitmap;
Canvascanvas;
Paintpaint;
@Override
publicvoidonCreate(BundlesavedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
imgView=(ImageView)findViewById(R.id.imgView);
DisplaycurrentDisplay=getWindowManager().getDefaultDisplay();
floatdw=currentDisplay.getWidth();
floatdh=currentDisplay.getHeight();
bitmap=Bitmap.createBitmap((int)dw,(int)dh,Config.ARGB_8888);
canvas=newCanvas(bitmap);
paint=newPaint();
paint.setColor(Color.GREEN);
paint.setStrokeWidth((float)10.00);//设置笔刷大小，自己的屏幕太犀利了
imgView.setImageBitmap(bitmap);
imgView.setOnTouchListener(this);
}
@Override
publicbooleanonTouch(Viewv,MotionEventevent){
intpointerCount=event.getPointerCount();
intpointerId=0;
intaction=（event.getAction()&MotionEvent.ACTION_MASK）%5;//统一单点和多点
switch(action){
caseMotionEvent.ACTION_DOWN:
if(pointerCount>1){
pointerId=(event.getAction()&MotionEvent.ACTION_POINTER_ID_MASK)>>>
MotionEvent.ACTION_POINTER_ID_SHIFT;
}
break;
caseMotionEvent.ACTION_MOVE:
if(pointerCount==2){
floatx=event.getX(1);
floaty=event.getY(1);
canvas.drawPoint((int)x,(int)y,paint);
imgView.invalidate();
}
break;
caseMotionEvent.ACTION_UP:
break;
}
returntrue;
}
}

public class Pointer2DrawActivity extends Activity implements OnTouchListener{ /** Called when the activity is first created. */ ImageView imgView; Bitmap bitmap; Canvas canvas; Paint paint; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); imgView = (ImageView)findViewById(R.id.imgView); Display currentDisplay = getWindowManager().getDefaultDisplay(); float dw = currentDisplay.getWidth(); float dh = currentDisplay.getHeight(); bitmap = Bitmap.createBitmap((int)dw, (int)dh, Config.ARGB_8888); canvas = new Canvas(bitmap); paint = new Paint(); paint.setColor(Color.GREEN); paint.setStrokeWidth((float) 10.00);//设置笔刷大小，自己的屏幕太犀利了 imgView.setImageBitmap(bitmap); imgView.setOnTouchListener(this); } @Override public boolean onTouch(View v, MotionEvent event) { int pointerCount = event.getPointerCount(); int pointerId = 0; int action = （event.getAction()&MotionEvent.ACTION_MASK） % 5;//统一单点和多点 switch(action){ case MotionEvent.ACTION_DOWN: if(pointerCount>1){ pointerId = (event.getAction()&MotionEvent.ACTION_POINTER_ID_MASK)>>> MotionEvent.ACTION_POINTER_ID_SHIFT; } break; case MotionEvent.ACTION_MOVE: if(pointerCount == 2){ float x = event.getX(1); float y = event.getY(1); canvas.drawPoint((int)x, (int)y, paint); imgView.invalidate(); } break; case MotionEvent.ACTION_UP: break; } return true; } }好了，Pointer2Draw终于按照想要的方式运行了。