UITableViewCell's subview not appearing - ios

Question

I have table cells that can expand to show some sub-detail, and I want a downward triangle to appear to let the user knows this is possible.
Here's the code that creates the triangle view...
-(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;
}
and the code the implements it...
-(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];
}
}
The code works as expected (creates a large red rectangle) if I comment out this line:
l.path = trianglePath.CGPath;
so I suppose there's something I'm not understanding about shape layers, but I'm using basically the same drawing code in another part of my app and it works fine.
The point and rect NSLog output checks out fine, too (even though it doesn't appear):
triangle origin is: {0, 0}
triangle size is: {100, 100}

Answer 1

you must use addLineToPoint: instead of moveToPoint: to create the path:
-(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;
}
also this line
self.openCloseTriangle = [self triangularViewWithWidth:100 height:100 pointsUp:NO];
is problematic: a view-property usually should be weak, as the view is owned by the view hierarchy, but if you assign the newly created view directly to such a property, it might be deallocated immediately. create a local view, add it to another view, than assign it to the property, that is weak.
my test code
#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