使用CoreMotion在后台获取加速度计数据 [英] Getting accelerometer data in background using CoreMotion

问题描述

我无法在后台接收加速计数据，尽管每个问题看似正确的解决方案 iPhone上的Nike + GPS如何在后台接收加速度计更新？

I'm unable to receive accelerometer data in the background, despite the seemingly correct solution per this question How Nike+ GPS on iPhone receives accelerometer updates in the background?

[_motionManager startAccelerometerUpdatesToQueue:[[NSOperationQueue alloc] init]
                                         withHandler:^(CMAccelerometerData *accelerometerData, NSError *error) {
                                             dispatch_async(dispatch_get_main_queue(), ^{
                                                 NSLog(@"perform");
                                                 [(id) self setAcceleration:accelerometerData.acceleration];
                                                 [self performSelectorOnMainThread:@selector(update) withObject:nil waitUntilDone:NO];
                                             });}];

每当应用程序在前台时都会记录执行，但每当我退出到后台时，它都会停止运行。有谁知道为什么会这样？我在背景模式中检查了位置更新...

perform is logged whenever the app is in the foreground, but whenever I exit out to background it stops running. Does anyone have any idea why this might be? I've checked "Location Updates" in Background Modes...

推荐答案

将此代码放在该行的前面（之后）制作一个名为bgTaskID的成员变量，类型为UIBackgroundTaskIdentifier）：

Put this code right in front of that line (after making a member variable called bgTaskID of type UIBackgroundTaskIdentifier):

UIApplication *application = [UIApplication sharedApplication];
        __weak __typeof(&*self)weakSelf = self;
        self.bgTaskID = [application beginBackgroundTaskWithExpirationHandler:^{
            __strong __typeof(&*weakSelf)strongSelf = weakSelf;

            NSLog(@"BG TASK EXPIRED!");

            if (strongSelf) {
                [application endBackgroundTask:strongSelf.bgTaskID];
                strongSelf.bgTaskID = UIBackgroundTaskInvalid;
            }
        }];

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