定义两个方法：

- (NSString *)dataFilePath;获取返回数据文件的完整路径名

- (void)applicationWillResignActive:(NSNotification *)notification;保存数据，参数notification的作用是在对象之间传递通知，保持通信。

#define kFilename        @"data.plist" - (NSString *)dataFilePath {
       NSArray *paths = NSSearchPathForDirectoriesInDomains(                                                          NSDocumentDirectory, NSUserDomainMask, YES);     NSString *documentsDirectory = [paths objectAtIndex:0]; return [documentsDirectory stringByAppendingPathComponent:kFilename]; }

 

- (void)applicationWillResignActive:(NSNotification *)notification {
       NSMutableArray *array = [[NSMutableArray alloc] init];     [array addObject:field1.text];     [array addObject:field2.text];     [array addObject:field3.text];     [array addObject:field4.text];     [array writeToFile:[self dataFilePath] atomically:YES]; }

（例子程序为保存四个textField的字符）

之后在viewDidLoad中添加代码：

- (void)viewDidLoad {
       [super viewDidLoad];     NSString *filePath = [self dataFilePath]; if ([[NSFileManager defaultManager] fileExistsAtPath:filePath]) {
           NSArray *array = [[NSArray alloc] initWithContentsOfFile:filePath];         field1.text = [array objectAtIndex:0];         field2.text = [array objectAtIndex:1];         field3.text = [array objectAtIndex:2];         field4.text = [array objectAtIndex:3];     }     UIApplication *app = [UIApplication sharedApplication];     [[NSNotificationCenter defaultCenter] addObserver:self         selector:@selector(applicationWillResignActive:)         name:UIApplicationWillResignActiveNotification object:app]; }