Xcode UIPickerView“NSInvalidArgumentExpression”？

Question

我正在尝试在 FlipsideViewController 中实现 UIPickerView，它只是一个设置选项卡。

这是.h文件中的相关代码：

@class FlipsideViewController;

@protocol FlipsideViewControllerDelegate<UIPickerViewDataSource, UIPickerViewDelegate>
- (void)flipsideViewControllerDidFinish:(FlipsideViewController *)controller;
@end

@property (strong, nonatomic) IBOutlet UIPickerView *Categories;

@property (strong, nonatomic) NSArray *categoriesData;

@property (strong, nonatomic) NSMutableArray* dataArray;

- (int)numberOfComponentsInPickerView:(UIPickerView *)pickerView;

- (NSInteger)Categories:(UIPickerView *)Categories numberOfRowsInComponent:(NSInteger)component;

- (NSString*)Categories:(UIPickerView *)Categories titleForRow:(NSInteger)row forComponent:(NSInteger)component;

这是.m文件中的相关代码：

    - (void)viewDidLoad
    {
        [super viewDidLoad];
        // Do any additional setup after loading the view, typically from a nib.

     _Categories = [[UIPickerView alloc] initWithFrame:CGRectMake((pickerWidth*4/3)/2-pickerWidth/2, 50.0f, pickerWidth, 200.0f)];

        _Categories.showsSelectionIndicator = true;

        [_Categories selectRow:2 inComponent:0 animated:YES];

        [self.view addSubview: _Categories];

        _dataArray = [[NSMutableArray alloc] init];

        [_dataArray addObject:@"One"];
        [_dataArray addObject:@"Two"];
        [_dataArray addObject:@"Three"];
        [_dataArray addObject:@"Four"];
        [_dataArray addObject:@"Five"];

        _categoriesData = _dataArray;

         _Categories.dataSource = (id)self;

         _Categories.delegate = (id)self;

}

- (int)numberOfComponentsInPickerView:(UIPickerView *)Categories
{
    return 1;
}

// The number of rows of data
- (NSInteger)Categories:(UIPickerView *)Categories numberOfRowsInComponent:(NSInteger)component
{
    return _categoriesData.count;
}

// The data to return for the row and component (column) that's being passed in
- (NSString*)Categories:(UIPickerView *)Categories titleForRow:(NSInteger)row forComponent:(NSInteger)component
{
    return [_categoriesData objectAtIndex:row];
}

抱歉，阅读内容有点过多。关键是在最后一部分，当- (NSInteger)Categories:(UIPickerView *)Categories numberOfRowsInComponent:(NSInteger)component 运行时，它返回一个“NSInvalidArgumentException”。我尝试在每种方法中重新初始化 dataArray 和 categoriesData，但无济于事。我不确定我应该怎么做......请帮忙。谢谢！

编辑：

发现错误。它在方法调用中......而不是指定我试图访问哪个 UIPickerView，而应该只放入一个通用的“UIPickerView”。所以，它应该是这样的：

- (NSString*)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component{}

- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component{}

不是这样的：

- (NSString*)pickerView:(UIPickerView *)Categories titleForRow:(NSInteger)row forComponent:(NSInteger)component

- (NSInteger)pickerView:(UIPickerView *)Categories numberOfRowsInComponent:(NSInteger)component{}

希望这可以帮助任何发现类似问题的人。

Answer 1

看起来 categoriesData 没有正确分配值。尝试更改下面的这一行并检查：-

self.categoriesData = _dataArray;