未调用NSLayoutManager委派

Question

我想知道为什么我的委托方法

- (void)layoutManager:(NSLayoutManager *)layoutManager
didCompleteLayoutForTextContainer:(NSTextContainer *)textContainer
                atEnd:(BOOL)layoutFinishedFlag

没有调用，我使用了以下代码：

self.storage = [[NSTextStorage alloc] initWithString:@"sdfsdf sdf sdf sdf sdf sdf Sdf sdf sdf "];
self.layout = [[NSLayoutManager alloc] init];
[self.storage addLayoutManager:self.layout];
self.layout.delegate = self;
NSTextContainer * container = [[NSTextContainer alloc] init];
[self.layout addTextContainer:container];

类中保留了强TextStorage和LayoutManager属性，但未调用委托方法！

Answer 1

当您在设置委托后修改NSTextStorage时，将调用委托方法。这是UIViewController中的一段代码：

- (void)viewDidLoad {
    [super viewDidLoad];
    self.layout = [[NSLayoutManager alloc] init];
    self.layout.delegate = self;
    self.storage = [[NSTextStorage alloc] init];
    [self.storage addLayoutManager:self.layout];
    NSTextContainer * container = [[NSTextContainer alloc] init];
    [self.layout addTextContainer:container];
    NSAttributedString *string = [[NSAttributedString alloc] initWithString:@"New string"];
    [self.storage setAttributedString:string];
}

- (void)layoutManager:(NSLayoutManager *)layoutManager
didCompleteLayoutForTextContainer:(NSTextContainer *)textContainer
                atEnd:(BOOL)layoutFinishedFlag
{
    NSLog(@"I'm here");
}

Answer 2

我发现当您将任何容器添加到UITextView时，也会调用委托方法。