android多点触摸实例及疑问
多点触摸的一个比较简明的示例：
示例代码出处：http://krvarma-android-samples.googlecode.com/svn/trunk/multitouchsample
?
在学习此示例的时候发现multitouch最多可以处理5个手指，5个以上的则不能处理~~
?
package com.varma.samples.multitouchsample;import java.util.ArrayList;import android.content.Context;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.DashPathEffect;import android.graphics.Paint;import android.graphics.PointF;import android.util.AttributeSet;//import android.util.FloatMath;import android.view.MotionEvent;import android.view.View;public class MultitouchView extends View {private static final int STROKE_WIDTH = 1;private static final int CIRCLE_RADIUS = 20;private ArrayList<PointF> touchPoints = null;private Paint drawingPaint = null;private boolean isMultiTouch = false;private int pathEffectPhase = 0;public MultitouchView(Context context) {super(context);initialize(context);}public MultitouchView(Context context, AttributeSet attrs, int defStyle) {super(context, attrs, defStyle);initialize(context);}public MultitouchView(Context context, AttributeSet attrs) {super(context, attrs);initialize(context);}@Overrideprotected void onDraw(Canvas canvas) {super.onDraw(canvas);if(touchPoints.size() > 0){DashPathEffect effect = new DashPathEffect(new float[] {7,7}, pathEffectPhase);PointF midpt = null;drawingPaint.setPathEffect(effect);for(int index=1; index<touchPoints.size(); ++index){midpt = getMidPoint(touchPoints.get(index - 1).x,touchPoints.get(index - 1).y,touchPoints.get(index).x,touchPoints.get(index).y);canvas.drawCircle(touchPoints.get(index - 1).x,touchPoints.get(index - 1).y, 1, drawingPaint);canvas.drawCircle(touchPoints.get(index - 1).x,touchPoints.get(index - 1).y, CIRCLE_RADIUS, drawingPaint);canvas.drawCircle(touchPoints.get(index).x,touchPoints.get(index).y, 1, drawingPaint);canvas.drawCircle(touchPoints.get(index).x,touchPoints.get(index).y, CIRCLE_RADIUS, drawingPaint);canvas.drawLine(touchPoints.get(index - 1).x,touchPoints.get(index - 1).y,touchPoints.get(index).x,touchPoints.get(index).y,drawingPaint);canvas.drawCircle(midpt.x,midpt.y, 10, drawingPaint);}++pathEffectPhase;invalidate();}}@Overridepublic boolean onTouchEvent(MotionEvent event) {super.onTouchEvent(event);int action = event.getAction() & MotionEvent.ACTION_MASK;switch(action){case MotionEvent.ACTION_DOWN:{invalidate();break;}case MotionEvent.ACTION_POINTER_DOWN:{isMultiTouch = true;setPoints(event);invalidate();break;}case MotionEvent.ACTION_POINTER_UP:{isMultiTouch = false;break;}case MotionEvent.ACTION_MOVE:{if(isMultiTouch){setPoints(event);invalidate();}break;}}return true;}private void initialize(Context context){drawingPaint = new Paint();drawingPaint.setColor(Color.RED);drawingPaint.setStrokeWidth(STROKE_WIDTH);drawingPaint.setStyle(Paint.Style.STROKE);drawingPaint.setAntiAlias(true);touchPoints = new ArrayList<PointF>();}public void setPoints(MotionEvent event){touchPoints.clear();int pointerIndex = 0;for(int index=0; index<event.getPointerCount(); ++index){pointerIndex = event.getPointerId(index);touchPoints.add(new PointF(event.getX(pointerIndex),event.getY(pointerIndex)));}}private PointF getMidPoint(float x1,float y1, float x2, float y2) {PointF point = new PointF();float x = x1 + x2;float y = y1 + y2;point.set(x / 2, y / 2);return point;}}?
示例图：