如何在UITextView中使用NSTextContainer和NSTextStorage显示属性化文本

Question

我试图通过使用UITextView和NSTextContainer在NSTextStorage中显示一些属性化文本，但在文本视图中没有看到任何绘制的内容(文本视图本身是按照需要用白色背景绘制的，但其中没有属性化文本)

不过，我只需将UITextView的UITextView属性设置为属性化文本字符串就可以做到这一点，但我想知道我在这里做错了什么，或者我误解了哪些概念。希望有人能解释。

- (void) test
{
    UIView *mainView = [[UIView alloc] initWithFrame:self.window.frame];
    mainView.translatesAutoresizingMaskIntoConstraints = NO;

    UITextView* textView = [[UITextView alloc] init];
    textView.translatesAutoresizingMaskIntoConstraints = NO;
    textView.backgroundColor = [UIColor whiteColor];

    [mainView addSubview:textView];
    [mainView removeConstraints:mainView.constraints];

    // layout constraints
    NSArray *constraintHorizontal = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|-[textView]-|" options:0 metrics:nil views:@{@"textView":mainView.subviews[0]}];
    NSArray *constraintVertical = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|-[textView(>=100)]" options:0 metrics:nil views:@{@"textView":mainView.subviews[0]}];

    [mainView addConstraints:constraintHorizontal];
    [mainView addConstraints:constraintVertical];

    NSString *data = @"This is some text where few words are colored and funky.  Some more garbage text. ";
    NSDictionary *attr = @{NSForegroundColorAttributeName:[UIColor redColor]};
    NSMutableAttributedString *textToShow = [[NSMutableAttributedString alloc] initWithString:data attributes:attr];

    NSRange r = {.location = 8, .length = 9};
    [textToShow addAttribute:NSForegroundColorAttributeName value:[UIColor greenColor] range:r];

    NSRange r2 = {.location = 23, .length = 4};
    [textToShow addAttribute:NSForegroundColorAttributeName value:[UIColor blueColor] range:r2];

    NSTextStorage* textStorage = [[NSTextStorage alloc]  initWithAttributedString:textToShow];

    CGSize cgs = textView.bounds.size;
    NSTextContainer *textcont = [[NSTextContainer alloc] initWithSize:cgs];

    // if i comment out these three lines and uncomment the
    //   following line (textView.attributedText .. ), then it works,
    NSLayoutManager *layoutManager = textView.layoutManager;
    [layoutManager addTextContainer:textcont];
    [textStorage addLayoutManager:layoutManager];

    //textView.attributedText = textToShow;

    textView.scrollEnabled = NO;

    UIViewController *vc = [[UIViewController alloc] init];
    vc.view = mainView;
    [vc.view layoutIfNeeded];
    self.window.rootViewController = vc;
}

更新上面的代码没有问题。我忘了在应用程序中添加以下行:didFinishLaunchingWithOptions。方法(在查看了用户的代码后，可以接受下面的答案)。

//self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]]; 
[self.window makeKeyAndVisible]; 

Answer 1

您的代码对我来说很好(Xcode 5.0.2)。这里提供了示例项目：

https://dl.dropboxusercontent.com/u/1365846/Test.zip https://dl.dropboxusercontent.com/u/1365846/Screen%20Shot%202014-02-09%20at%2023.11.22.png

根据“任择议定书”，他漏掉了以下几行：

self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
[self.window makeKeyAndVisible];

见评论。