//可以通过代码创建或者绑定到storyboard上的UIView
    DrawView *drawView=[[DrawView alloc] init];
    drawView.frame=CGRectMake(0, 100, self.view.bounds.size.width, 300);
    [self.view addSubview:drawView];
    //设置画板背景颜色
    drawView.backgroundColor=[UIColor blackColor];
    //设置画笔宽度
    drawView.lineWidth=5;
    //设置画笔颜色
    drawView.lineColor=[UIColor redColor];