iOS

Question

我正在学习 CoreGraphic 并想做一个简单的游戏，但坚持用贝塞尔曲线绘制东西，我想在子视图中画一个三角形，但总是出错，我希望它适合 1/4正方形视图

我的代码：

UIBezierPath* trianglePath = [UIBezierPath bezierPath];
[trianglePath moveToPoint:CGPointMake(0, 0)];
[trianglePath addLineToPoint:CGPointMake(self.mainView.frame.size.width/2, self.mainView.frame.size.height/2)];
[trianglePath addLineToPoint:CGPointMake(self.mainView.frame.size.width, 0)];
[trianglePath closePath];

CAShapeLayer *triangleMaskLayer = [CAShapeLayer layer];
[triangleMaskLayer setPath:trianglePath.CGPath];

UIView *firstView = [[UIView alloc] initWithFrame:CGRectMake(0,0, self.mainView.frame.size.width, self.mainView.frame.size.height)];

firstView.backgroundColor = [UIColor colorWithWhite:.75 alpha:1];
firstView.layer.mask = triangleMaskLayer;
[self.mainView addSubview:firstView];

看起来像这样：

Answer 1

如果尺寸不正确，您可能在 AutoLayout 完成工作之前就创建了三角形。

为确保您的 self.mainView 大小正确，请在控制器 viewDidLayoutSubviews 方法中创建三角形。

另外请注意 viewDidLayoutSubviews 可能会被调用多次。

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
}

- (void) viewDidLayoutSubviews {
    [super viewDidLayoutSubviews];

    if (self.mainView.subviews.count == 0) {
        UIBezierPath* trianglePath = [UIBezierPath bezierPath];
        [trianglePath moveToPoint:CGPointMake(0, 0)];
        [trianglePath addLineToPoint:CGPointMake(self.mainView.frame.size.width/2, self.mainView.frame.size.height/2)];
        [trianglePath addLineToPoint:CGPointMake(self.mainView.frame.size.width, 0)];
        [trianglePath closePath];

        CAShapeLayer *triangleMaskLayer = [CAShapeLayer layer];
        [triangleMaskLayer setPath:trianglePath.CGPath];

        UIView *firstView = [[UIView alloc] initWithFrame:CGRectMake(0,0, self.mainView.frame.size.width, self.mainView.frame.size.height)];

        firstView.backgroundColor = [UIColor colorWithWhite:.75 alpha:1];
        firstView.layer.mask = triangleMaskLayer;
        [self.mainView addSubview:firstView];

    }
}
- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

iOS - 在子视图中绘制贝塞尔曲线路径

iOS - Draw Bezier Path in Subview

core-graphics

objective-c