NSUserDefaults保存用户名和密码

#import "ViewController.h"

@interface ViewController ()
@property (weak, nonatomic) IBOutlet UITextField *nameTextField;
@property (weak, nonatomic) IBOutlet UITextField *ageTextField;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    //1.测试部分：获取沙盒的Library目录
    NSArray *libraryPaths = NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES);
    NSString *libraryPath = [libraryPaths lastObject];
    NSLog(@"libraryPath:%@",libraryPath);

    //2.初始化数据（从第四步保存的数据，读取它，并显示）
    [self initDataByUserDefault];

    //3.在用户将后台程序移除后，需要知道针对这个动作的触发时间/方法（通知）
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(applicationWillDidEnterBackground:) name:UIApplicationDidEnterBackgroundNotification object:[UIApplication sharedApplication]];

    //4.在后面
}

- (void)initDataByUserDefault{
    //获取全局的NSUserDefaults对象
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    //使用defaults对象来获取保存的数据
    NSString *nameStr = [defaults objectForKey:@"name"];
    NSString *ageStr = [defaults objectForKey:@"age"];
    //将上步获取的数据，赋值给nameTextField
    if (nameStr) {
        self.nameTextField.text = nameStr;
    }
    if (ageStr) {
        self.ageTextField.text = ageStr;
    }

}

- (void)applicationWillDidEnterBackground:(NSNotification *)notitication{
    NSLog(@"测试：进入后台时机");
    //4.在触发方法中去保存你要保存的数据。
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    [defaults setObject:self.nameTextField.text forKey:@"name"];
    [defaults setObject:self.ageTextField.text forKey:@"age"];

    //强制将用户输入的名字和年龄数据保存到硬盘中
    //这里不是自己决定的，由系统决定 ，存在Library目录下。
    [defaults synchronize];
}

@end