使用 Objective-C 以编程方式创建 UIView 以在纵向和横向中工作

Question

我要在目标 c 中创建一个视图，上面有两个标签，label1 有单行，label2 是基于内容的多行。

根据标签中的内容我想调整视图高度，我该怎么做？

视图的宽度应该是屏幕宽度的 20 左右，下面的代码可以纵向显示，但横向显示不正确，它在右侧裁剪。我怎样才能为横向显示正确的 20？

肖像

风景

    UIView *emptyTreeView = [[UIView alloc] initWithFrame:CGRectMake(20,20,self.view.frame.size.width - 40,400)];
    UILabel *label1 =  [[UILabel alloc] initWithFrame:CGRectMake(30.0, 30.0, self.view.frame.size.width - 100, 30.0)];
    UILabel *label2 = [[UILabel alloc] initWithFrame:CGRectMake(30.0, 90.0, self.view.frame.size.width - 100, 100.0)];
    emptyTreeView.backgroundColor=[UIColor blueColor];
    label1.backgroundColor = [UIColor redColor];
    label1.textAlignment = NSTextAlignmentCenter;
    label1.textColor = [UIColor blackColor];
    label1.font = [UIFont boldSystemFontOfSize:18];
    label1.numberOfLines = 0;
    label1.text = @"The Page Cannot be displayed.";
    label2.backgroundColor = [UIColor whiteColor];
    label2.textAlignment = NSTextAlignmentCenter;
    label2.textColor = [UIColor grayColor];
    label2.font = [UIFont systemFontOfSize:15];
    label2.numberOfLines = 0;
    label2.text = @"Please use this feature or contact your internal contact person directly.";
    [emptyTreeView addSubview:label1];
    [emptyTreeView addSubview:label2];
    [self.view addSubview:emptyTreeView];

我做错了什么吗？

Answer 1

一些观察：

1. 不要在viewDidLayoutSubviews 中添加子视图。这仅用于调整frame 值。

2. 如果您引用self.view，请引用它的bounds，而不是它的frame。前者用于self.view 内的子视图坐标。后者在其父视图的坐标系中（现在可能不会引入任何差异，但只是错误的坐标系。

3. 如果您希望视图在旋转时调整大小，请设置其autoresizingMask，例如

   emptyTreeView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleBottomMargin;
   

   或者

   emptyTreeView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleBottomMargin;
   

4. 如今，设置帧值和自动调整蒙版大小有点不合时宜。我们通常会使用约束，例如

   - (void)viewDidLoad {
       [super viewDidLoad];
   
       UIView *emptyTreeView = [[UIView alloc] init];
       UILabel *label1 =  [[UILabel alloc] init];
       UILabel *label2 = [[UILabel alloc] init];
       emptyTreeView.backgroundColor = [UIColor blueColor];
       label1.backgroundColor = [UIColor redColor];
       label1.textAlignment = NSTextAlignmentCenter;
       label1.textColor = [UIColor blackColor];
       label1.font = [UIFont boldSystemFontOfSize:18];
       label1.numberOfLines = 0;
       label1.text = @"The Page Cannot be displayed.";
       label2.backgroundColor = [UIColor whiteColor];
       label2.textAlignment = NSTextAlignmentCenter;
       label2.textColor = [UIColor grayColor];
       label2.font = [UIFont systemFontOfSize:15];
       label2.numberOfLines = 0;
       label2.text = @"Please use this feature or contact your internal contact person directly.";
       [emptyTreeView addSubview:label1];
       [emptyTreeView addSubview:label2];
       [self.view addSubview:emptyTreeView];
   
       emptyTreeView.translatesAutoresizingMaskIntoConstraints = false;
       label1.translatesAutoresizingMaskIntoConstraints = false;
       label2.translatesAutoresizingMaskIntoConstraints = false;
   
       [NSLayoutConstraint activateConstraints:@[
           [emptyTreeView.leftAnchor constraintEqualToAnchor:self.view.safeAreaLayoutGuide.leftAnchor constant:20],
           [emptyTreeView.rightAnchor constraintEqualToAnchor:self.view.safeAreaLayoutGuide.rightAnchor constant:-10],
           [emptyTreeView.topAnchor constraintEqualToAnchor:self.view.safeAreaLayoutGuide.topAnchor constant:20],
   
           [label1.leftAnchor constraintEqualToAnchor:emptyTreeView.leftAnchor constant:20],
           [label1.rightAnchor constraintEqualToAnchor:emptyTreeView.rightAnchor constant:-20],
           [label1.topAnchor constraintEqualToAnchor:emptyTreeView.topAnchor constant:20],
   
           [label2.leftAnchor constraintEqualToAnchor:emptyTreeView.leftAnchor constant:20],
           [label2.rightAnchor constraintEqualToAnchor:emptyTreeView.rightAnchor constant:-20],
           [label2.topAnchor constraintEqualToAnchor:label1.bottomAnchor constant:20],
   
           [emptyTreeView.bottomAnchor constraintEqualToAnchor:label2.bottomAnchor constant:20]
       ]];
   }
   

   注意translatesAutoresizingMaskIntoConstraints 是false 和约束。