Question

我在一个单独的视图中有很多行的UIPickerView，settingsViewController。选择行时，它会通过NSUserDefaults将数据传递给mainViewController。但是，如果我返回settingsViewController并且在不更改行的情况下按下保存按钮 - pickerView似乎发送值'nil'？

这是UIPickerView的代码和传递行的代码。

//PickerViewCode
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    [picker selectRow:[defaults integerForKey:@"pickerRow"] inComponent:0 animated:YES];
}

}

- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView {
return 1;

}

- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:  
(NSInteger)component {
{
    if ([skolor count] == 0)
        return 1;
    return [skolor count];
}}

- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row 
forComponent:(NSInteger)component {
return [skolor objectAtIndex:row];
}


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

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
[defaults setInteger:row forKey:@"pickerRow"];

//Passing pickerViewValue
- (IBAction)selectedRow:(id)sender {

SchoolSoftViewController2 *vc1 = [self.storyboard 
instantiateViewControllerWithIdentifier:@"webview1"];
NSString *urlString = [valdSkola absoluteString];
[[NSUserDefaults standardUserDefaults] setObject:urlString  forKey:@"UserURL"];
[self presentViewController:vc1 animated:YES completion:nil];

}

Answer 1

NSUserDefaults在使用setObject：forKey：方法调用设置后不会立即保存信息。要强制它保存，请在默认情况下设置urlString之后，但在呈现视图控制器之前告诉它进行同步。

NSString *urlString = [valdSkola absoluteString];
[[NSUserDefaults standardUserDefaults] setObject:urlString  forKey:@"UserURL"];
[[NSUserDefaults standardUserDefaults] synchronize];
[self presentViewController:vc1 animated:YES completion:nil];

还有你设置行的地方：

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
[defaults setInteger:row forKey:@"pickerRow"];
[defaults synchronize];

Answer 2

尝试设置选择器选择值。就像这样。

int row = [pickerView selectedRowInComponent：COMPONANT_INDEX]; NSString * str = [YOUR_ARRAY objectAtIndex：row]; //如果数组为空，它可能会崩溃

[[NSUserDefaults standardUserDefaults] setObject：str forKey：@“UserURL”]; [[NSUserDefaults standardUserDefaults] synchronize];

在你的情况下， NSString * urlString = [valdSkola absoluteString]; //这将返回一个零

单独视图中的UIPickerView会失去价值

2 个答案: