ios - Obj-C 委托(delegate)在单独的文件中实现

Question

我正在尝试清理我的代码。我的 ViewController 中有 3 个 pickerView，我想在单独的文件中实现委托(delegate)。

id imp = [[HourPickerImplementation alloc] init];
self.hourPicker.dataSource = imp;
self.hourPicker.delegate = imp;

HourPickerImplementation.h:

@interface HourPickerImplementation : NSObject <UIPickerViewDataSource, UIPickerViewDelegate>

@end

HourPickerImplementation.m:

@implementation HourPickerImplementation {
  NSMutableArray *_pickerData;
}

- (id)init {
  _pickerData = [[NSMutableArray alloc] initWithCapacity:25];
  for (int i = 0; i < 25; i++) {
    [_pickerData addObject:[NSString stringWithFormat:@"%d H.", i]];
  }
  return self;
}

- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView {
  return 1;
}

- (NSInteger)pickerView:(UIPickerView *)pickerView
numberOfRowsInComponent:(NSInteger)component {
  return _pickerData.count;
}

- (UIView *)pickerView:(UIPickerView *)pickerView
            viewForRow:(NSInteger)row
          forComponent:(NSInteger)component
           reusingView:(UIView *)view {
  UIImage *img = [UIImage imageNamed:@"icon_lock.png"];
  UIImageView *temp = [[UIImageView alloc] initWithImage:img];
  temp.frame = CGRectMake(51, 20, 20, 20);

  UILabel *channelLabel =
      [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 50, 60)];
  channelLabel.text =
      [NSString stringWithFormat:@"%@", [_pickerData objectAtIndex:row]];
  channelLabel.textColor = [UIColor whiteColor];
  channelLabel.backgroundColor = [UIColor clearColor];

  UIView *tmpView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 110, 60)];
  [tmpView insertSubview:temp atIndex:0];
  [tmpView insertSubview:channelLabel atIndex:1];

  return tmpView;
}

不幸的是，它给了我这个错误:

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x170099c80 V:[UIImageView:0x12751a110(55)]>

Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.
2015-08-26 10:30:30.489 bollywood[675:103276] Unable to simultaneously satisfy constraints.
    Probably at least one of the constraints in the following list is one you don't want. Try this: (1) look at each constraint and try to figure out which you don't expect; (2) find the code that added the unwanted constraint or constraints and fix it. (Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints) 
(
    "<NSLayoutConstraint:0x17009a540 V:[UIImageView:0x12751c480(55)]>",
    "<NSLayoutConstraint:0x17009a590 V:[UIImageView:0x12751c5c0(50)]>",
    "<NSLayoutConstraint:0x17009a810 V:[UIImageView:0x12751c480]-(12)-[UIImageView:0x12751c5c0]>",
    "<NSLayoutConstraint:0x17009a900 UITableViewCellContentView:0x12751bcd0.bottomMargin == UIImageView:0x12751c5c0.bottom>",
    "<NSLayoutConstraint:0x17009aa40 UIImageView:0x12751c480.top == UITableViewCellContentView:0x12751bcd0.topMargin + 12>",
    "<NSLayoutConstraint:0x1740961c0 'UIView-Encapsulated-Layout-Height' V:[UITableViewCellContentView:0x12751bcd0(139)]>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x17009a540 V:[UIImageView:0x12751c480(55)]>

Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful. 

我做错了什么？它在一个文件中工作，但看起来很糟糕。

Answer 1

该错误暗示您的单元格中的约束无法满足，因为它们中的一组要求布局无法实现。

查看输出，以下行可能是问题所在:

<NSLayoutConstraint:0x1740961c0 'UIView-Encapsulated-Layout-Height' V:[UITableViewCellContentView:0x12751bcd0(139)]>

此约束可能由选择器 View 根据您从 rowForHeightForComponent 返回的内容生成。这个高度好像是139pts。

首先检查您的委托(delegate)方法是否实际被调用。你说你拆分了文件。猜测是系统将其设置为 139，因为它在移动后没有看到您的新委托(delegate)代码。

您的其他约束似乎是 2 个高度为 55 和 50 的图像，间隔为 12，顶部边距为 12。约束中的总固定高度为 117。我注意到您也在使用布局来保证边距。如果这不是您想要的，请将其更改为与实际顶部相对。

因此，您的问题是单元格内容希望以固定大小/间距打包，但当其设置为 139pts 时仍无法与顶部和底部对齐。

我的建议是检查您对返回的行高的计算。

您可以通过将底部图像和内容 View 底部对齐的底部约束更改为图像底部从内容 View 底部固定 >=0 来解决约束问题.通过使这个固定 >=0 约束将不再失败。不过，您会看到底部有一个空隙，您现在可以用它来处理您在代码中返回的高度之间的不匹配。