ios - 表头 View 自动布局问题

Question

我正在将自定义 UIView 的 XIB 文件加载为 View Controller 内的 uitableview 的标题 View 。

xib 文件的文件所有者是 View Controller 。我在 uiviewcontroller 中声明了 viewcontroller 和 uiview 的接口(interface)。

ViewController.h

      @class ZeroStateView;

      @interface ViewController : UIViewController <UITableViewDataSource, UITableViewDelegate>

      @property (nonatomic, weak) IBOutlet CustomUITableView *tableView;
      @property (nonatomic,strong) NSMutableArray *dataArray;
      @property (weak, nonatomic) IBOutlet ZeroStateView *zeroStateView;


      @end


     @interface ZeroStateView : UIView
     @property (weak, nonatomic) IBOutlet AutoLayoutLabel *titleLabel;
     @property (weak, nonatomic) IBOutlet UIImageView *titleIcon;

     - (void)updateView;

     @end

ViewController.m

    - (void)prepareHeaderViewForZeroState{
            ZeroStateView *sizingView = [ZeroStateView new];
            [[[NSBundle mainBundle] loadNibNamed:@"ZeroStateView" owner:self options:nil] objectAtIndex:0];
            sizingView = self.zeroStateView;
           [sizingView updateView];

           self.tableView.tableHeaderView = sizingView;

           UIView *headerView = self.tableView.tableHeaderView;



           CGFloat height = [headerView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize].height;

         CGRect headerFrame = headerView.frame;
         headerFrame.size.height = height;
         headerView.frame = headerFrame;


         self.tableView.tableHeaderView = headerView;
     }

    @end

    @implementation ZeroStateView

    -(void)updateView{
      self.titleIcon.alpha = 0.5;

      UIFontDescriptor *titleFontDescriptor = [UIFontDescriptor preferredFontDescriptorWithTextStyle:UIFontTextStyleSubheadline];

      self.titleLabel.text =  @"This is a long text message and its really long. This is a long text message and its really long. This is a long text message and its really long. This is a long text message and its really long. This is a long text message and its really long. This is a long text message and its really long. This is a long text message and its really long. This is a long text message and its really long. ";

     }

AutolayoutLabel 类重写了以下方法:

   - (void)setBounds:(CGRect)bounds {
      [super setBounds:bounds];

      // For multiline label, preferredMaxLayoutWidth always matches the frame width
      if (self.numberOfLines == 0 && bounds.size.width != self.preferredMaxLayoutWidth) {
          self.preferredMaxLayoutWidth = self.bounds.size.width;
          [self setNeedsUpdateConstraints];
      }
   }

由 systemLayoutSizeFittingSize:UILayoutFittingCompressedSize 计算的高度返回 0。因此，我得到以下 View 作为表头 View :

当我如下添加实际高度时，uilabel 溢出。我期望 uiview 随着标签高度的增长而增长。

 headerFrame.size.height = self.sizingView.frame.size.height;

这是 UIViews 约束的屏幕截图:

我在这里错过了什么？有人可以指出我吗？

更新 我创建了一个示例 project让你们检查到底是什么问题。

Answer 1

我以不同的方式重新实现了您到目前为止的内容。首先，我删除了 ZeroStateView.xib 中嵌入了 UIImageView 和 UILabel 的 UIView。 xib的已经是一个UIView，所以没有必要再添加一个UIView给它。

接下来我改变了周围的约束。我不记得具体更改了哪些约束，所以我将在此处列出它们:

1. UIImageView 的约束
   • 将 X 中心与 SuperView 对齐
   • 宽度 = 60
   • 高度= 56
   • Superview 的顶部空间 = 37
   • UILabel 的底部空间 = 31
2. UILabel 的约束
   • Superview 的剩余空间 = 15
   • Superview 的正确空间 = 15
   • 到 Superview 的底部空间 = 45
   • UIImageView 的顶部空间 = 31

进入代码。在 ViewController.h 中，据我所知，IBOutlet 没有做任何事情，所以我将该属性更改为读取 @property(强，非原子) ZeroStateView *zeroStateView;

现在是重要的变化:ViewController.m。有两个 UITableViewDelegate 方法将替换 prepareHeaderViewForZeroState。在 viewDidLoad 中，初始化 zeroStateView 并将 TableView 的委托(delegate)设置为 self。

- (void)viewDidLoad
{
    //...

    // Load the view
    self.zeroStateView = [[[NSBundle mainBundle] loadNibNamed:@"ZeroStateView" owner:self options:nil] firstObject];
    [self.zeroStateView updateView];
    self.zeroStateView.backgroundColor = [UIColor darkGrayColor];

    // Set self for table view delegate for -heightForHeaderInSection: and viewForHeaderInSection:
    self.dataTable.delegate = self;
}

现在我们是 TableView 的委托(delegate)，我们得到两个方法调用，这将允许我们自定义标题 View 并适本地设置它的高度。

- (UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section
{
    // This will set the header view to the zero state view we made in viewDidLoad
    return self.zeroStateView;
}

- (CGFloat)tableView:(UITableView *)tableView heightForHeaderInSection:(NSInteger)section
{
    // sizeToFit describes the size that the label can fit itself into.
    // So we are saying that the label can use the width of the view and infinite height.
    CGSize sizeToFit = CGSizeMake(self.view.frame.size.width, MAXFLOAT);

    // Then we ask the label to tell us how it can fit in that size.
    // The label will respond with the width of the view and however much height it needs
    // to display its text. This is the magic of how it grows vertically.
    CGSize size = [self.zeroStateView.titleLabel sizeThatFits:sizeToFit];

    // Add the height the label needs to the overall zero state view. This should be changed
    // to the height of the UIImage + the height we just got + the whitespace above and below
    // each of these views. You can handle that part.
    return self.zeroStateView.frame.size.height + size.height;
}

我将更改上传到 Dropbox here .