iOS:保存双选择器的设置(数据持久性)

Question

所以我有一个双选择器，用户可以将每个轮子设置为他们想要的，然后按下一个按钮来显示他们的选择。易于清洁和简单，但我想存储该数据以备后用，以便在他们关闭应用程序并再次打开它后它不会消失。现在，我知道如何使用 datePicker，但不知道如何使用 doublePicker。所以我的问题是如何通过将 datePickers 信息保存和检索到 doublePicker 来调整我的代码？

这是我的日期选择器代码:

    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];

// Pulling the date out of my picker
NSDate *selectedDate = [self.datePicker date];

[defaults setObject:selectedDate forKey:@"DatePickerViewController.selectedDate"];

然后再次检索它:

    - (void)viewDidLoad
{
    [super viewDidLoad];

    // Get the date. I'm going to use a little shorthand instead of creating 
    // a variable for the instance of `NSUserDefaults`.
    NSDate *storedDate = [[NSUserDefaults standardUserDefaults] objectForKey:@"DatePickerViewController.selectedDate"];

    // Setting the date on the date picker. I'm passing `NO` to `animated:` 
    // because I'm performing this before the view is on screen, but after
    // it has been loaded.
    [self.datePicker setDate:storedDate animated:NO];
}

任何帮助将不胜感激，thx :)

Answer 1

在你的UIPickerViewDelegate中:

        - (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component
{
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];

    [defaults setInteger:row forKey:[NSString stringWithFormat:@"DoublePickerViewController.%i", component]];
}

获取数据:

        for (int i = 0; i < doublePicker.numberOfComponents; i++) {
        NSInteger *storedInteger = [[NSUserDefaults standardUserDefaults] integerForKey:[NSString stringWithFormat:@"DoublePickerViewController.%i", i];
[doublePicker selectRow:storedInteger inComponent:i animated:NO];
    }

用于存储多个值:

在你的UIPickerViewDelegate中:

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

{
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];

    NSArray *oldArray = [defaults arrayForKey:[NSString      stringWithFormat:@"DoublePickerViewController.%i", component]];

    //Make a mutable version so we can change it
    NSMutableArray *newArray = [oldArray mutableCopy];
    if (!newArray) {
        newArray = [NSMutableArray array];
    }
    //Add The Latest Row To The end of the array. We wrap it in an NSNumber so it can be in an array
    [newArray addObject:[NSNumber numberWithInteger:row]];

    //If you want to have a limit on the amount of values that can be stored then use this
    int maxValues = 5;
    if (newArray.count >= maxValues) {
        //Remove the oldest object
        [newArray removeObjectAtIndex:0];
    }
    [defaults setObject:newArray forKey:[NSString      stringWithFormat:@"DoublePickerViewController.%i", component]];
}

获取数据:

        for (int i = 0; i < doublePicker.numberOfComponents; i++) {
        NSArray *storedIntegers = [[NSUserDefaults standardUserDefaults] arrayForKey:   [NSString stringWithFormat:@"DoublePickerViewController.%i", i];
        //I don't know what values you want, but to get an int out of the array:
        //int integer = [(NSNumber *)[storedIntegers objectAtIndex:0] intValue];
        //And to set the row for a component:
        //[doublePicker selectRow:storedInteger inComponent:i animated:NO];
    }