DrawRect

在RootView.m里重写如下方法

- (void)drawRect:(CGRect)rect{    // 初始化一个路线//    self.path = [UIBezierPath bezierPath];  // 点之间的过度效果//    _path.lineCapStyle = kCGLineCapRound; // 设置节点过度效果//    _path.lineJoinStyle = kCGLineJoinRound; // 设置终点过度效果//    _path.lineWidth = 3.0; // 设置线宽//    //    [_path moveToPoint:CGPointMake(100, 100)];//    //    [_path addLineToPoint:CGPointMake(150, 150)];//    [path addLineToPoint:CGPointMake(180, 130)];//    [path addLineToPoint:CGPointMake(200, 170)];//    [path addLineToPoint:CGPointMake(120, 180)];//    //    [path stroke];    // 得到上下文 1 在drawRect拿到上下文 2 通过一个image图片拿到上下文//    CGContextRef context = UIGraphicsGetCurrentContext();//    // 设置了画笔的颜色//    CGContextSetStrokeColorWithColor(context, [UIColor redColor].CGColor);//    // 设置画笔的粗细//    CGContextSetLineWidth(context, 2.0);    for (UIBezierPath *path in self.paths) {        [path stroke];    }}- (NSMutableArray *)paths{    if (!_paths) {        _paths = [NSMutableArray array];    }    return _paths;}- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{    // 获取touch对象    UITouch *touch = [touches anyObject];    // 获取touch起始点    CGPoint point = [touch locationInView:touch.view];    // 创建路径对象    UIBezierPath *path = [UIBezierPath bezierPath];    path.lineWidth = 3.0;    path.lineCapStyle = kCGLineCapRound;    path.lineJoinStyle = kCGLineJoinRound;    // 设置起点    [path moveToPoint:point];    // 添加路径    [self.paths addObject:path];}- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{    // 获取touch对象    UITouch *touch = [touches anyObject];    CGPoint point = [touch locationInView:touch.view];    UIBezierPath *path = [self.paths lastObject];    [path addLineToPoint:point];    [self setNeedsDisplay];}- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event{    [self touchesMoved:touches withEvent:event];}