UITableViewCell的子视图未出现

Question

我的表格单元格可以扩展以显示一些子详细信息，并且我希望显示一个向下的三角形，以使用户知道这是可能的。

这是创建三角形视图的代码...

-(UIView *)triangularViewWithWidth:(CGFloat)width height:(CGFloat)height pointsUp:(BOOL)pointsUp {
UIBezierPath *trianglePath = [UIBezierPath bezierPath];
if(pointsUp){
    [trianglePath moveToPoint:CGPointMake(width / 2, 0)];
    [trianglePath moveToPoint:CGPointMake(width, height)];
    [trianglePath moveToPoint:CGPointMake(0, height)];
    [trianglePath closePath];
} else {
    [trianglePath moveToPoint:CGPointMake(0, 0)];
    [trianglePath moveToPoint:CGPointMake(width, 0)];
    [trianglePath moveToPoint:CGPointMake(width / 2, height)];
    [trianglePath closePath];
}
CAShapeLayer *l = [CAShapeLayer layer];
l.path = trianglePath.CGPath;

UIView *triangleView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, width, height)];
triangleView.layer.mask = l;
return triangleView;
}

以及实现它的代码...

-(void)drawTriangle {
if([self.detail.subDetails count]){
    self.openCloseTriangle = [self triangularViewWithWidth:100 height:100 pointsUp:NO];
    NSLog(@"triangle origin is: %@", NSStringFromCGPoint(self.openCloseTriangle.frame.origin));
    NSLog(@"triangle size is: %@", NSStringFromCGSize(self.openCloseTriangle.frame.size));
    self.openCloseTriangle.backgroundColor = [UIColor redColor];
    [self.contentView addSubview:self.openCloseTriangle];
    [self.contentView bringSubviewToFront:self.openCloseTriangle];
}
}

如果我注释掉此行，代码将按预期工作（创建一个大的红色矩形）：

l.path = trianglePath.CGPath;

因此，我想我对形状图层尚不了解，但是我在应用程序的另一部分使用了基本相同的绘图代码，因此效果很好。

点和矩形NSLog输出也可以很好地进行检查（即使它没有出现）：

三角形的原点是：{0，0}三角形的大小是：{100，100}

Answer 1

您必须使用addLineToPoint:而不是moveToPoint:创建路径：

-(UIView *)triangularViewWithWidth:(CGFloat)width height:(CGFloat)height pointsUp:(BOOL)pointsUp {
    UIBezierPath *trianglePath = [UIBezierPath bezierPath];
    if(pointsUp){
        [trianglePath moveToPoint:CGPointMake(width / 2, 0)];
        [trianglePath addLineToPoint:CGPointMake(width, height)];
        [trianglePath addLineToPoint:CGPointMake(0, height)];
        [trianglePath closePath];
    } else {
        [trianglePath moveToPoint:CGPointMake(0, 0)];
        [trianglePath addLineToPoint:CGPointMake(width, 0)];
        [trianglePath addLineToPoint:CGPointMake(width / 2, height)];
        [trianglePath closePath];
    }
    CAShapeLayer *l = [CAShapeLayer layer];
    l.path = trianglePath.CGPath;

    UIView *triangleView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, width, height)];
    triangleView.layer.mask = l;    
    return triangleView;
}

---

也是这条线

self.openCloseTriangle = [self triangularViewWithWidth:100 height:100 pointsUp:NO];

这是有问题的：由于视图属于视图层次结构，因此视图属性通常应该较弱，但是如果将新创建的视图直接分配给此类属性，则可能会立即将其释放。 创建一个本地视图，将其添加到另一个视图，而不是将其分配给该属性，即弱视图。

---

我的测试代码

#import "ViewController.h"

@interface ViewController ()
@property (weak) UIView *openCloseTriangle;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    [self drawTriangle];
}

-(UIView *)triangularViewWithWidth:(CGFloat)width height:(CGFloat)height pointsUp:(BOOL)pointsUp {
    UIBezierPath *trianglePath = [UIBezierPath bezierPath];
    if(pointsUp){
        [trianglePath moveToPoint:CGPointMake(width / 2, 0)];
        [trianglePath addLineToPoint:CGPointMake(width, height)];
        [trianglePath addLineToPoint:CGPointMake(0, height)];
        [trianglePath closePath];
    } else {
        [trianglePath moveToPoint:CGPointMake(0, 0)];
        [trianglePath addLineToPoint:CGPointMake(width, 0)];
        [trianglePath addLineToPoint:CGPointMake(width / 2, height)];
        [trianglePath closePath];
    }
    CAShapeLayer *l = [CAShapeLayer layer];
    l.path = trianglePath.CGPath;

    UIView *triangleView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, width, height)];
    triangleView.layer.mask = l;    
    return triangleView;
}


-(void)drawTriangle {
    UIView * v= [self triangularViewWithWidth:100 height:100 pointsUp:NO];
    self.openCloseTriangle = v;
    NSLog(@"triangle origin is: %@", NSStringFromCGPoint(self.openCloseTriangle.frame.origin));
    NSLog(@"triangle size is: %@", NSStringFromCGSize(self.openCloseTriangle.frame.size));
    self.openCloseTriangle.backgroundColor = [UIColor redColor];
    [self.view addSubview:self.openCloseTriangle];
}

@end