当app进入后台时如何继续运行NSTimer [英] how to keep running NSTimer when app goes in background

问题描述

我正在创建益智游戏应用程序，并且我正在使用NSTimer显示时间（即01:20）。当应用程序在后台运行时NSTimer暂停但我想继续它甚至应用程序处于后台状态。

I am creating puzzle game application and in that I am displaying time (i.e 01:20) using NSTimer. NSTimer is paused when application gone in background but i want to continue it even application is in background state.

例如当应用程序进入时，计时器计数为15秒背景，我放置5秒并变为前景现在我需要将计时器计数更改为20秒

for example timer count is 15 sec when app gone in background and I put it for 5 sec and become in foreground now I need to timer count changes to 20 sec

我搜索了很多，但没有得到很好的答案。
所以请建议我如何实现这一目标。

I have searched a lot but didn't get good answer. So Please suggest me how can I achieve this.

推荐答案

不要将计时器视为对象计时的东西。可以把它想象成一个以给定频率脉冲的物体。要测量时间，请记录开始时间并将其与当前时间进行比较。

Don't think of a timer as an object for timing something. Think of it rather as an object that pulses at a given frequency. To measure time, record a start time and compare it to the current time.

要记录开始时间，请将其写入文件，如下所示，可能在appWillResignActive：

To record the start time, write it to a file as follows, probably in appWillResignActive:

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
NSString *path = [paths objectAtIndex:0];
NSString *filename = [path stringByAppendingPathComponent:@"saveme.dat"];

NSData * data = [NSKeyedArchiver archivedDataWithRootObject:self.startDate];
[data writeToFile:filename atomically:NO];
// invalidate timer

当appWillBecomeActive：

When appWillBecomeActive:

NSData *data = [NSData dataWithContentsOfFile:filename];    // using the same code as before
self.startDate = [NSKeyedUnarchiver unarchiveObjectWithData:data];
// start a timer for the purpose of pulsing only

此时的经过时间是：

NSDate *now = [NSDate date];
NSTimeInterval = [now timeIntervalSinceDate:self.startDate];

所有上述内容均可在不在后台运行的情况下完成。如果您确实需要在后台触发计时器，请参阅苹果参考。在后台执行下。简而言之，您可以这样做，但Apple会在批准应用程序之前让您满足几个标准 - 例如它必须是有限的并为用户提供实用程序。

All of the foregoing can be done without running in the background. If you really need a timer to fire in the background, see this apple ref. Under "Background Execution". In a nutshell, you can do it, but Apple will make you meet several criteria before approving the app -- like it must be finite and provide utility for the user.

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