Question

我正在尝试使用以下代码的基本UI选择器视图

- (void)viewDidLoad
{
    [super viewDidLoad];
    self.MainPicker.delegate = self;
    self.MainPicker.dataSource = self;
    [self.MainPicker selectRow:1 inComponent:0 animated:NO];
    _countryNames = @[@"Australia (AUD)", @"China (CNY)",
                      @"France (EUR)", @"Great Britain (GBP)", @"Japan (JPY)"];
    //NSLog(@"%@", [_countryNames objectAtIndex:0]);

    _exchangeRates = @[ @0.9922f, @6.5938f, @0.7270f,
                        @0.6206f, @81.57f];
    // Do any additional setup after loading the view, typically from a nib.
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

-(void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row
      inComponent:(NSInteger)component
{
    float rate = [_exchangeRates[row] floatValue];
    float dollars = 10.0;
    float result = dollars * rate;

    NSString *resultString = [[NSString alloc] initWithFormat:
                              @"%.2f USD = %.2f %@", dollars, result,
                              _countryNames[row]];
    NSLog(@"%@",resultString);
    [pickerView reloadAllComponents];
}
- (IBAction)Submit:(id)sender {
}
-(IBAction)textFieldReturn:(id)sender
{
    [sender resignFirstResponder];
}
- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView{
    return 1;
}

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

- (NSString *)pickerView:(UIPickerView *)pickerView
             titleForRow:(NSInteger)row
            forComponent:(NSInteger)component
{
    return _countryNames[row];
}
@end

当我说明

时获得例外

2013-12-09 15：46：11.174 pickerExample [20718：a0b] - [UIView numberOfComponentsInPickerView：]：发送到无法识别的选择器实例0x9880e80 2013-12-09 15：46：11.260 pickerExample [20718：a0b] * 由于未捕获的异常'NSInvalidArgumentException'而终止应用程序，原因：' - [UIView numberOfComponentsInPickerView：]：发送到无法识别的选择器实例0x9880e80'。

我已将数据源和委托链接到当前视图控制器。任何人都可以指导我出错的地方!!

Answer 1

在设置[self.MainPicker selectRow:1 inComponent:0 animated:NO];之前，您的问题是调用datasource方法。实际上你甚至试图在setting up UIPicker之前选择一行所以在调用此方法之前设置_countryNames和_exchangeRates，如下所示......

viewDidLoad

中的

初始化数据源

_countryNames = @[@"Australia (AUD)", @"China (CNY)",
                      @"France (EUR)", @"Great Britain (GBP)", @"Japan (JPY)"];
    //NSLog(@"%@", [_countryNames objectAtIndex:0]);

    _exchangeRates = @[ @0.9922f, @6.5938f, @0.7270f,
                        @0.6206f, @81.57f];

//方法调用

    self.MainPicker.delegate = self;
        self.MainPicker.dataSource = self;
        [self.MainPicker selectRow:1 inComponent:0 animated:NO];

UIPicker查看IOS7异常

1 个答案: