ios - CAShapeLayer mask View

Question

我有一个问题。我在网上寻找答案，但我不明白为什么不起作用。我一定是犯了一些我想不通的愚蠢错误。

如果我做:

- (void)viewDidLoad
{
    [super viewDidLoad];

    UIView * view = [[UIView alloc]initWithFrame:CGRectMake(10, 10, 300, 400)];
    view.backgroundColor = [UIColor blueColor];
    [self.view addSubview:view];

}

它会在屏幕上创建蓝色 View ，但如果我让

- (void)viewDidLoad
{
    [super viewDidLoad];

    UIView * view = [[UIView alloc]initWithFrame:CGRectMake(10, 10, 300, 400)];
    view.backgroundColor = [UIColor blueColor];
    [self.view addSubview:view];

    CAShapeLayer * layer = [[CAShapeLayer alloc]init];
    layer.frame = CGRectMake(10, 10, 30, 30);
    layer.fillColor = [[UIColor blackColor] CGColor];

    view.layer.mask = layer;

}

它没有显示任何内容。

如果我理解正确，它应该屏蔽在 (10,10,30,30)？

Answer 1

您需要在 CAShapeLayer 上设置路径:

- (void)viewDidLoad
{
    [super viewDidLoad];


    UIView * view = [[UIView alloc]initWithFrame:CGRectMake(10, 10, 300, 400)];
    view.backgroundColor = [UIColor blueColor];
    [self.view addSubview:view];

    CAShapeLayer * layer = [[CAShapeLayer alloc]init];
    layer.frame = view.bounds;
    layer.fillColor = [[UIColor blackColor] CGColor];

    layer.path = CGPathCreateWithRect(CGRectMake(10, 10, 30, 30), NULL);

    view.layer.mask = layer;
}