iOS: Saving a double picker's settings (data persistence)

问题

So I have a double picker where the user sets each wheel to what they want, and then press a button which will display their choice. Easy clean and simple, but I want to store that data for later so that it does not disappear after they close the app and re-open it again. Now, I know how to do it with a datePicker, but not a doublePicker. So my question is how do I tweak my code from saving and retrieving a datePickers info into a doublePicker?

Here is my code for the datePicker:

    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];

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

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

And then retrieving it again:

    - (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];
}

Any help would be appreciated, thx :)

回答1:

In your UIPickerViewDelegate:

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

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

To get the data out:

        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];
    }

For storing multiple values:

In your UIPickerViewDelegate:

- (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]];
}

To get the data out:

        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];
    }

来源：https://stackoverflow.com/questions/18112748/ios-saving-a-double-pickers-settings-data-persistence

标签

ios

persistence

uipickerview