UIPickerView ShowsSelectionIndicator 不起作用

Posted 2023-02-24

【中文标题】UIPickerView ShowsSelectionIndicator 不起作用

【英文标题】：UIPickerView ShowsSelectionIndicator does not work

【发布时间】：2017-08-31 12:33:42

【问题描述】：

尽管据说指标从ios7开始总是显示，但我得到这样的东西：

这是我的实现：

class TimePicker: UIPickerView 

    override func awakeFromNib() 
        self.delegate = self
        self.dataSource = self
        self.showsSelectionIndicator = true
    



extension TimePicker: UIPickerViewDelegate 
    func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? 
        let minutes = [0,1,2,3,4,5,6,7,8,9,10]
        let seconds = [0,5,10,15,20,25,30,35,40,45,50,55]
        switch component 
        case 0: return minutes[row].description
        default: return seconds[row].description
        
    


extension TimePicker: UIPickerViewDataSource 

    func numberOfComponents(in pickerView: UIPickerView) -> Int 
        return 2
    

    func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int 
        switch component 
        case 0:
            return 11
        default:
            return 12

        
    

我的代码有什么问题，指标没有显示，这让它看起来很糟糕？

【参考方案1】：

您能否尝试使用 UIPickerViewDelegate 的其他替代委托方法来配置组件中的行视图，即

- (UIView *)pickerView:(UIPickerView *)pickerView viewForRow:(NSInteger)row forComponent:(NSInteger)component reusingView:(UIView *)view 
UILabel* label = nil;
if (view == nil) 
    view = [[UIView alloc] init];
    view.backgroundColor = [UIColor blueColor];
    label = [[UILabel alloc] initWithFrame:CGRectMake(10, 10, 60, 22)];

    NSString *rowTextValue;
    switch component 
    case 0: rowTextValue = [Nsstring StringWithFormat:@"%d",minutes[row]]; break;
    default: rowTextValue = [Nsstring StringWithFormat:@"%d", seconds[row]]; break;
    
    label.text = rowTextValue;
    [view addSubview:label];

   if (label == nil) 
    NSLog(@"%@",view.subviews);
    label = view.subviews[0]; // I do get subviews here.
   
return view;

【讨论】：

因为我不是 swift 的人，你可以得到这个方法的 swift 版本作为 pickerView(_:viewForRow:forComponent:reusing:) 方法来提供组件行的内容。我发布这个是因为 Swift 和 ObjC 在理解上非常相似