UIView改变边框宽度中间内容大小不变

最近有个需求是，保证中间圆大小不变，动态改变边线宽度。这里比较简单的方法有两种：view和UIBezierPath

//view

    

    UIView *view1 = [[UIView alloc] initWithFrame:CGRectMake(10, 100, 100, 100)];

    view1.backgroundColor = [UIColor redColor];

    view1.layer.cornerRadius = 50;

    view1.clipsToBounds = YES;

    view1.layer.borderColor = [UIColor greenColor].CGColor;

    view1.layer.borderWidth = 10;

    [self.view addSubview:view1];

    

    UIView *view2 = [[UIView alloc] initWithFrame:CGRectMake(200, 100, 120, 120)];

    view2.backgroundColor = [UIColor redColor];

    view2.layer.cornerRadius = 60;

    view2.clipsToBounds = YES;

    view2.layer.borderColor = [UIColor greenColor].CGColor;

    view2.layer.borderWidth = 20;

    view2.center = CGPointMake(255, 150);

    [self.view addSubview:view2];

    

    //这里保证填充大小不变  view的宽、高的增量和cornerRadius的增量、borderWidth的增量比为：2：1：1

    

    UIView *view3 = [[UIView alloc] initWithFrame:CGRectMake(10, 250, 100, 100)];

    view3.backgroundColor = [UIColor redColor];

    view3.layer.cornerRadius = 50;

    view3.clipsToBounds = YES;

    [self.view addSubview:view3]; 

 //贝塞尔曲线

    

    UIBezierPath *path=[UIBezierPath bezierPath];

    [path addArcWithCenter:CGPointMake(60, 150) radius:50 startAngle:2 endAngle:M_PI*2+2

                 clockwise:YES];

    

    CAShapeLayer *layer1=[CAShapeLayer layer];

    layer1.path=path.CGPath;

    layer1.fillColor = [UIColor redColor].CGColor;

    layer1.strokeColor = [UIColor greenColor].CGColor;

    layer1.lineWidth=10;

    [self.view.layer addSublayer:layer1];

    

    UIBezierPath *path1=[UIBezierPath bezierPath];

    [path1 addArcWithCenter:CGPointMake(250, 150) radius:55 startAngle:2 endAngle:M_PI*2+2

                 clockwise:YES];

    

    CAShapeLayer *layer2=[CAShapeLayer layer];

    layer2.path=path1.CGPath;

    layer2.fillColor = [UIColor redColor].CGColor;

    layer2.strokeColor = [UIColor greenColor].CGColor;

    layer2.lineWidth=20;

    [self.view.layer addSublayer:layer2];

    

    //这里要保证中间填充部分大小不变的情况下，改变lineWidth，lineWidth的增量与radius增量的比例为2：1

    

    UIBezierPath *path2=[UIBezierPath bezierPath];

    [path2 addArcWithCenter:CGPointMake(250, 350) radius:50 startAngle:2 endAngle:M_PI*2+2

                  clockwise:YES];

    

    CAShapeLayer *layer3=[CAShapeLayer layer];

    layer3.path=path2.CGPath;

    layer3.fillColor = [UIColor redColor].CGColor;

    layer3.strokeColor = [UIColor greenColor].CGColor;

    layer3.lineWidth=10;

    [self.view.layer addSublayer:layer3];

这里需要注意的就是：

对view的操作 borderWidth的大小不影响view的frame。当borderWidth增大时，view的frame不变，那么中间部分的直径就会减小；

对path的操作 lineWidth的大小会影响视图的frame。当lineWidth增大时，view的frame会增大lineWidth，这样只增加lineWidth的大小，中间部分直径不变