Question

ios怎么实现后台定时

Answer 1

步骤一：在Info.plist中，添加"Required background modes"键，value为：App plays audio

步骤二：

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions

{

self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];

// Override point for customization after application launch.

NSError *setCategoryErr = nil;

NSError *activationErr = nil;

[[AVAudioSession sharedInstance]

setCategory: AVAudioSessionCategoryPlayback

error: &setCategoryErr];

[[AVAudioSession sharedInstance]

setActive: YES

error: &activationErr];

self.window.backgroundColor = [UIColor whiteColor];

[self.window makeKeyAndVisible];

return YES;

}
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步骤三：将以下代码添加到appDelegate文件中的- (void)applicationDidEnterBackgroundUIApplication *)application函数，也可添加到在具体类中注册的应用进入后台后的通知方法

- (void)applicationDidEnterBackground:(UIApplication *)application{

UIApplication* app = [UIApplication sharedApplication];

__block UIBackgroundTaskIdentifier bgTask;

bgTask = [app beginBackgroundTaskWithExpirationHandler:^{

dispatch_async(dispatch_get_main_queue(), ^{

if (bgTask != UIBackgroundTaskInvalid)

{

bgTask = UIBackgroundTaskInvalid;

}

});

}];

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

dispatch_async(dispatch_get_main_queue(), ^{

if (bgTask != UIBackgroundTaskInvalid)

{

bgTask = UIBackgroundTaskInvalid;

}

});

});

}
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完成以上步骤你会发现，程序进入后台后仍可运行定时器！