1

有没有办法为选择器设置默认值?我保存了所有选择器中最后选择的行,我希望能够让选择器在启动时加载那些保存的行。到目前为止,我已经找到了这段代码:

[settingsPagePicker selectRow:3 inComponent:0 animated:YES];

它有效,但仅当用户点击选择器时。我需要它在应用程序首次加载时工作。如果我将此代码放在 viewDidLoad 应用程序将崩溃。任何人都知道将它放在我的代码中以使其工作的正确位置吗?

感谢您的时间!

4

2 回答 2

6

在调用 -selectRow:inComponent:animated 以确保该索引处有可用数据(示例代码中的 3)之前,您是否检查了 settingsPagePicker 的数据源?

您如何为数据源加载数据?您可以先在 viewDidLoad 中初始化数据源,然后在知道有可用数据后调用 selectRow。

更新:这是您的代码应该是什么样子或类似的东西:

- (void)viewDidLoad
{
    [super viewDidLoad];
    pickerDataSource = [[NSMutableArray alloc] init];
    [pickerDataSource addObject:@"Item 01"];
    [pickerDataSource addObject:@"Item 02"];
    [pickerDataSource addObject:@"Item 03"];
    [pickerDataSource addObject:@"Item 04"];

    // Might want to move this to -viewWillAppear:animated
    [settingsPagePicker selectRow:3 inComponent:0 animated:YES];
}

- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component
{
    if (pickerView == settingsPagePicker)
    {
        return [pickerDataSource objectAtIndex:row];
    }
    return @"";
}

- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component 
{
    if (pickerView == settingsPagePicker)
    {
        return [pickerDataSource count];
    }
    return 0;
}

- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)thePickerView
{
    return 1;
}
于 2009-10-26T17:29:48.763 回答
2

这是我班上的一些方法。

- (void)viewDidLoad {
   [super viewDidLoad];
   currentNumbersOfComponents = 1;
   //[picker selectRow:2 inComponent:0 animated:NO];
}
- (void) viewDidAppear:(BOOL)animated{
   [super viewDidAppear:animated];
   [picker selectRow:2 inComponent:0 animated:YES];
}

#pragma mark picker view data source methods

- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView{
    return currentNumbersOfComponents;
}

- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component{
    return 5;
}

picker.dataSource 是 self

于 2009-10-26T17:15:17.063 回答