我知道了和我没有按照顺序绘制图形有关我把代码改成下面这样就好了
path.moveTo(30,40);
path.lineTo(30,140);
//path.moveTo(50,170);
path.cubicTo(30,140,30,160,50,170);
//path.moveTo(50,170);
path.lineTo(50,190);
path.lineTo(70,190);
path.lineTo(70,170);
path.cubicTo(70,170,90,160,90,140);
path.lineTo(90,40);
path.lineTo(30,40);
谢谢!!!