自由划线的好用工具类

public class MyPaintView extends View {
    private List allPoints=new ArrayList();
    //接受context以及属性集合(宽度，高度等)
    public MyPaintView(Context context, AttributeSet attrs) {
        super(context, attrs);
        super.setOnTouchListener(new OnTouchListenerImp());
    }
    private class OnTouchListenerImp implements OnTouchListener{

        public boolean onTouch(View v, MotionEvent event) {
            Point p=new Point((int)event.getX(),(int)event.getY());
            if(event.getAction()==MotionEvent.ACTION_DOWN){
//用户按下，表示重新开始保存点
                MyPaintView.this.allPoints=new ArrayList();
                MyPaintView.this.allPoints.add(p);
            }
            else if(event.getAction()==MotionEvent.ACTION_UP){
//用户松开
                MyPaintView.this.allPoints.add(p);
                MyPaintView.this.postInvalidate();//重绘图像
            }