关于视图层次结构，需要澄清

Question

在此代码示例中，我尝试生成以下视图层次结构

窗口 ->背景图片->滚动视图->文本视图

我所看到的只是

窗口->背景图片

请问我缺少什么？

-(void) viewWillAppear:(BOOL)animated {

    UIScrollView *scrollWindow = [[UIScrollView alloc] 
                 initWithFrame:CGRectMake(30, 30, 440, 212)];

    UITextView *scrollableText = [[UITextView alloc] init];

    [scrollableText setEditable:NO];
    [scrollableText setText:@"Why, hello there"];

    [scrollWindow addSubview:scrollableText];

    UIImage *backgroundImage = [[UIImage alloc] initWithCGImage:
             [UIImage imageNamed:@"about_bg.png"].CGImage];
    UIImageView *backgroundView = [[UIImageView alloc] 
             initWithImage:backgroundImage];

    [backgroundView addSubview:scrollWindow];

    [[self view] addSubview:backgroundView];

}

Answer 1

安德鲁关于不让滚动视图成为背景 UIImageView 视图的子视图是正确的。但滚动视图是不可见的。仅显示其内容 (scrollableText)。而且您还没有设置 scrollableText 的框架，因此它实际上也是不可见的。像这样初始化：

[scrollableText setEditable:NO];
[scrollableText setText:@"Why, hello there"];
[scrollableText setFrame:CGRectMake(0, 0, 100, 100)];

你应该看到它。

Answer 2

您需要的是这样的层次结构：

Window
  background image view
  scroll view
    text view

尝试将两个子视图添加到您的窗口中，而不是将它们全部作为子视图相互推入。''-

   - (void) viewWillAppear:(BOOL)animated {

      UIScrollView *scrollWindow = [[UIScrollView alloc] initWithFrame:CGRectMake(30, 30, 440, 212)];

      UITextView *scrollableText = [[UITextView alloc] init];

      UIImageView *backgroundView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"about_bg.png"]];

      scrollableText.editable = NO;
      scrollableText.text = @"Why, hello there";

      [scrollWindow addSubview:scrollableText];

      [self.view addSubview:backgroundView];
      [self.view addSubview:scrollWindow];
    }