使用 GCD 计时器
直接将 CLCountButton 拖入工程
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view.
CLCountButton *button = [CLCountButton buttonWithType:UIButtonTypeCustom];
button.frame = CGRectMake(([[UIScreen mainScreen] bounds].size.width - 120) / 2, 200, 120, 40);
[self.view addSubview:button];
[button addTarget:self action:@selector(timeButtonClick:) forControlEvents:UIControlEventTouchUpInside];
}
- (void)timeButtonClick:(CLCountButton *)sender {
[sender startCount];
}
app 如果进入后台，计时器会暂停，苹果给出的三种类型的程序能够保持在后台运行：音频播放类，位置更新类等，这里采用 音频播放 的方式来解决
- 在
info.plist中添加Required background modes键，value 为App plays audio or streams audio/video using AirPlay - 在
TARGETS->Signing&Capabilities->Background Modes勾选Audio, AirPlay, and Picture in Picture - 在
AppDelegate.m中导入#import <AVFoundation/AVFoundation.h>添加如下代码：
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
// Override point for customization after application launch.
[[AVAudioSession sharedInstance] setCategory: AVAudioSessionCategoryPlayback error: NULL];
[[AVAudioSession sharedInstance] setActive: YES error: NULL];
return YES;
}
- (void)applicationDidEnterBackground:(UIApplication *)application {
UIApplication *taskApplication = [UIApplication sharedApplication];
__block UIBackgroundTaskIdentifier backgroundTask;
backgroundTask = [taskApplication beginBackgroundTaskWithExpirationHandler:^{
dispatch_async(dispatch_get_main_queue(), ^{
if (backgroundTask != UIBackgroundTaskInvalid) {
backgroundTask = UIBackgroundTaskInvalid;
}
});
}];
dispatch_async(dispatch_get_global_queue(0, 0), ^{
dispatch_async(dispatch_get_main_queue(), ^{
if (backgroundTask != UIBackgroundTaskInvalid) {
backgroundTask = UIBackgroundTaskInvalid;
}
});
});
}