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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]; }