退出时保存当前状态，重新打开应用时自动重新加载

问题描述

I'm creating a simple app to simply save a person's name and a number associated with this person. I've created a class for person like this:

@interface Person : NSObject {
    NSString *name;
    NSInteger serialNumber;
}

In the mainViewController, I've created an input text field to enter the name and then automatically assign a number to the person, also 2 UILabel to show the inputted name and the serialNumber.

However, after quitting the app and re-open, all labels cleared. What I'm trying to do is to keep these variables as they were when quitting the app and display in the labels. Hence, I created 2 variables in the app delegate and tried to use applicationWillTerminate: in the app delegate to save . In the mainViewController I've inserted these codes after each time I typed in a new name:

NameAppDelegate *appDelegate = (NameAppDelegate *)[[UIApplication sharedApplication] delegate];
appDelegate.lastPerson.name = aPerson.name;
//currentPerson is an instance variable of the app delegate
appDelegate.lastPerson.serialNumber = aPerson.serialNumber;
NSLog(@"aPerson.serialNumber = %i", aPerson.serialNumber);
NSLog(@"appDelegate.lastPerson.serialNumber = %i", appDelegate.lastPerson.serialNumber);

However, each time I typed a new name, the console showed a change in aPerson.serialNumber (which is in mainViewController) BUT not the appDelegate.lastPerson.serialNumber (which is always equal to zero).

Is there anything wrong with the codes above?

解决方案

Easy to do with NSUserDefaults, here's some code to get you started:

- (void)applicationDidFinishLaunching:(UIApplication *)application {
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    appDelegate.lastPerson.name = [defaults stringForKey:@"Name"];
    appDelegate.lastPerson.serial = [defaults stringForKey:@"Serial"];

    [window addSubview:[flipViewController view]];
    [window makeKeyAndVisible];
}

-(void)applicationWillTerminate:(UIApplication *)application {
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    [defaults setString:appDelegate.lastPerson.name forKey:@"Name"];
    [defaults setString:appDelegate.lastPerson.serial forKey:@"Serial"];
    [defaults synchronize];
}

You can check if either of the strings are nil after loading which will indicate no stored value and you should then ask the user for input.

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