ios - 退出应用程序时无法使用 NSUserDefaults 保存整数

Question

我是一个初学者，想在我的应用程序中存储一个 int 值(高分)，这样当用户从多任务处理中关闭应用程序并再次打开它时，它将获取数据并显示它。

我尝试使用 NSUserDefaults，但当我再次打开应用程序时它没有出现。这是我使用的代码:

// Used this to load the high score from the memory
  highscoreInt = (int)[[NSUserDefaults standardUserDefaults] integerForKey:@"highscore"]; 

// And this to store it, later in the code
- (void)applicationWillTerminate:(UIApplication *)application
{
    [[NSUserDefaults standardUserDefaults] setInteger:highscoreInt forKey:@"highscore"];
    [[NSUserDefaults standardUserDefaults] synchronize];
}

Answer 1

我会将整数包装在 NSNumber 对象中，并将其放入 applicationDidEnterBackground 中，如下所示:

// Use this method to release shared resources, save user data, 
// invalidate timers, and store enough application state information to 
// restore your application to its current state in case it is terminated later.

- (void)applicationDidEnterBackground:(UIApplication *)application
{
  highscoreInt = (int)[[NSUserDefaults standardUserDefaults] integerForKey:@"highscore"]; 

  [[NSUserDefaults standardUserDefaults] setObject:[NSNumber numberWithInt:highScoreInt] forKey:@"highscore"];
  [[NSUserDefaults standardUserDefaults] synchronize];

}

当你需要加载你的乐谱时，在你想要加载它的任何方法中执行以下操作:

int highScore = [[NSUserDefaults standardUserDefaults] objectForKey:@"highscore"];

你会发现这个 link有助于阅读 NSUserDefaults。