iphone – 用户退出应用程序时保存核心数据？

2024年1月11日 167次阅读

当用户按下主页按钮时,我正在尝试保存Core Data.我想从-applicationDidEnterBackground执行此操作：但它没有被调用.这可能是因为您无法从此处保存Core Data或仅因为没有足够的时间来完成操作.然而,它确实起作用于-applicationWillResignActive：我只是好奇哪个是最好的委托方法来执行此操作以及为什么-applicationDidEnterBackground：不起作用.

(正如你从输出中看到的那样,两个方法都被调用,如果我从-applicationWillResignActive中删除了保存：根本没有任何事情发生,所以当一个人阻塞另一个时不是这种情况)

// CALLS SAVE
- (void)applicationWillResignActive:(UIApplication *)application {
    [[self model] saveCoreData:@"SAVE FROM: applicationWillResignActive"];
    NSLog(@"APPDEL: %s", __PRETTY_FUNCTION__);
}

// DOES NOT CALL SAVE
- (void)applicationDidEnterBackground:(UIApplication *)application {
    [[self model] saveCoreData:@"SAVE FROM: applicationDidEnterBackground"];
    NSLog(@"APPDEL: %s", __PRETTY_FUNCTION__);
}

.

// CONSOLE OUTPUT
2013-03-21 cvb[6724:907] APPDEL: -[AppDelegate applicationWillResignActive:]
2013-03-21 cvb[6724:907] APPDEL: -[AppDelegate applicationDidEnterBackground:]
2013-03-21 cvb[6724:907]  
2013-03-21 cvb[6724:907] SAVE: SAVE FROM: applicationWillResignActive
2013-03-21 cvb[6724:907] SAVE: Saving successful ...

编辑：

这就是我最后所做的：

- (void)applicationDidEnterBackground:(UIApplication *)application {
    __block UIBackgroundTaskIdentifier bgTask = [application beginBackgroundTaskWithExpirationHandler:^{
        [application endBackgroundTask:bgTask];
        bgTask = UIBackgroundTaskInvalid;
    }];
    [[self model] saveCoreData:@"[ENTERING BACKGROUND]"];
}

最佳答案 查看
UIApplicationDelegate protocol reference.

基本上,这是您可能对applicationDidEnterBackground感兴趣的部分：

You should perform any tasks relating to adjusting your user interface
before this method exits but other tasks (such as saving state) should
be moved to a concurrent dispatch queue or secondary thread as needed.
Because it’s likely any background tasks you start in
applicationDidEnterBackground: will not run until after that method
exits, you should request additional background execution time before
starting those tasks. In other words, first call
beginBackgroundTaskWithExpirationHandler: and then run the task on a
dispatch queue or secondary thread.

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