Ios 无法在CAShapeLayer上填充UIBezier

我想在自定义视图中添加几个点，创建一条路径，关闭它并用颜色填充。在for循环中，我水平放置数千个点并用线连接它们。但是，我无法绘制闭合贝塞尔路径。有什么问题

UIBezierPath *path = [UIBezierPath bezierPath];
[path moveToPoint:CGPointMake(0, screenHeight/2)];
 [path addLineToPoint:CGPointMake(0, screenHeight/2)];
[path addLineToPoint:CGPointMake(0, screenHeight/2)];

for (int i=0; i<=screenWidth; i+=screenWidth/stepNo) {
    [path addLineToPoint:CGPointMake(i, screenHeight/2)];
}
[path addLineToPoint:CGPointMake(screenWidth, screenHeight/2)];
[path addLineToPoint:CGPointMake(screenWidth, screenHeight)];
    [path addLineToPoint:CGPointMake(0, screenHeight)];

[path closePath];


//Create a CAShapeLayer that uses that UIBezierPath:
CAShapeLayer *shape = [CAShapeLayer layer];
shape.path = path.CGPath;
shape.fillColor = [UIColor colorWithRed:255/255.0 green:20/255.0 blue:147/255.0 alpha:1].CGColor;

// 5
[self.view.layer addSublayer:shape];

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也许你可以试着在你的图层上设置背景色，以确保它与你期望的帧一起显示。我的子图层被显示是因为如果我使用构造而不是for循环[path addLineToPoint:CGPointMakescreenWidth，screenHeight/2]；我可以看到矩形。然后你能试着这样构造你的路径吗：UIBezierPath*path=[UIBezierPath-bezierPath]；[路径移动点：CGPointMake0，屏幕高度/2]；[path addLineToPoint:CGPointMake0，屏幕高度]；[path addLineToPoint:CGPointMakescreenWidth，screenHeight]；[path addLineToPoint:CGPointMakescreenWidth，screenHeight/2]；[path closePath]；我已经尝试过这种结构，所有的东西都显示正确。然而，我有超过4个点，这就是为什么我需要循环。stepNo是如何定义的？