ios - UIPicker selectRow 不工作-这段代码有什么问题？

Question

我正在尝试为 UIPickerView 设置一个默认值。但是，无论我将其设置为哪个值，它始终默认为 1。下面的方法可以很好地加载选择器，我可以选择它。那么，我做错了什么？这是代码。

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

    arrayNo = [[NSMutableArray alloc] init];
    [arrayNo addObject:@" 1 "];
    [arrayNo addObject:@" 2 "];
    [arrayNo addObject:@" 3 "];
    [arrayNo addObject:@" 4 "];
    [arrayNo addObject:@" 5 "];

    [pickerView selectRow:4 inComponent:0 animated:YES];
    mlabel.text= [arrayNo objectAtIndex:[pickerView selectedRowInComponent:0]];    

}

Picker 的数据源方法:

- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component
{

    mlabel.text = [arrayNo objectAtIndex:row];
    NSNumberFormatter * f = [[NSNumberFormatter alloc] init];

    [f setNumberStyle:NSNumberFormatterDecimalStyle];

    NSNumber * myNumber = [f numberFromString:[arrayNo objectAtIndex:row]];

    [f release];

    prefs = [NSUserDefaults standardUserDefaults];

    NSInteger myInteger = [myNumber integerValue];


    // save level
    [prefs setInteger:myInteger forKey:@"myInt"];

    // saving it all
    [prefs synchronize];


}

- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component;
{
    return [arrayNo count];
}

Answer 1

如果我把它放在这个方法中，它会起作用:

-(void) viewWillAppear: (BOOL) animated