Xcode UIPickerView "NSInvalidArgumentExpression"？

Question

我试图在一个UIPickerView中实现一个FlipsideViewController，这只是一个设置选项卡。

下面是.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;

下面是.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，如果你读的太多了。关键是，在最后一部分中，当运行- (NSInteger)Categories:(UIPickerView *)Categories numberOfRowsInComponent:(NSInteger)component时，它返回一个"NSInvalidArgumentException“。我尝试在每种方法中重新初始化dataArray和categoriesData，但都没有效果。我不确定我该怎么做..。请帮帮忙。谢谢!

编辑：

发现了错误。那是在方法呼叫中。与其指定我试图访问的UIPickerView，相反，我应该只添加一个通用的"UIPickerView“。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{}

希望这能帮助任何人发现类似的问题。

Answer 1

看起来，categoriesData没有正确地分配值。尝试在下面更改这一行并检查：-

self.categoriesData = _dataArray;