问题描述：
app需要在收到MQTT消息的时候震动30秒和通知栏展示本地通知，一分钟之后移除通知栏消息，这必然涉及到倒计时，出现的问题是当app在后台的时候会出现会出现30秒左右的保活，定时器不走了。。。。。
官网链接：
https://developer.apple.com/documentation/uikit/uiapplication/1623031-beginbackgroundtaskwithexpiratio/
https://developer.apple.com/documentation/backgroundtasks/choosing_background_strategies_for_your_app?language=objc
解决办法：
应用在后台时可以播放声音信息。
可以利用此模式播放无声音乐，App 进入后台后，播放无声音乐，配合beginBackgroundTaskWithName对系统申请后台使用时间，可以使APP在后台长时间保活。
应用提供位置信息 应用场景：在后台时需要不断通知用户位置更新信息。
通过后台持续定位App，可以实现App后台保活。
以下Demo可以实现解决这个问题，但是发现在iOS15以上的系统还是存在问题。
https://github.com/QiShare/QiAppRunInBackground
https://gitee.com/msmasker/back-runing-demo
解决iOS15以上系统该问题：
https://www.jianshu.com/p/4c02230677f3
以上是Swift写的，改写OC如下：
//
// XTBackRunningManager.m
// XTBackRunningDemo
//
// Created by mshi on 2022/1/20.
//
#import "C2AppBackRunningManager.h"
#import <UIKit/UIKit.h>
#import <AVFoundation/AVFoundation.h>
@interface C2AppBackRunningManager ()
@property (nonatomic, strong) AVAudioPlayer *audioPlayer;
@property (nonatomic, strong) AVAudioEngine *audioEngine;
@property (nonatomic,assign) UIBackgroundTaskIdentifier backgroundTaskIdentifier;
@property (nonatomic, strong) NSTimer *applyTimer;
@property (nonatomic, strong) NSTimer *taskTimer;
@end
@implementation C2AppBackRunningManager
+ (instancetype)shareManager {
static C2AppBackRunningManager *manager = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
manager = [[C2AppBackRunningManager alloc] init];
});
return manager;
}
//- (instancetype)init {
// self = [super init];
// if (self) {
//// [self addNoti];
// // 获取定位权限
// [self.locationManager requestAlwaysAuthorization];
// [self.locationManager requestWhenInUseAuthorization];
// }
// return self;
//}
- (void)startBackgroundTask: (UIApplication *)app {
self.backgroundTaskIdentifier = [app beginBackgroundTaskWithExpirationHandler:^{
[app endBackgroundTask:self.backgroundTaskIdentifier];
self.backgroundTaskIdentifier = UIBackgroundTaskInvalid;
[self applyForMoreTime];
}];
[self.applyTimer invalidate];
self.applyTimer = nil;
[self.taskTimer invalidate];
self.taskTimer = nil;
self.taskTimer = [NSTimer scheduledTimerWithTimeInterval:5 target:self selector: @selector(doSomething) userInfo:nil repeats:YES];
}
- (void)stopBackgroundTask {
[self.applyTimer invalidate];
self.applyTimer = nil;
[self.taskTimer invalidate];
self.taskTimer = nil;
}
- (void)doSomething {
DLog(@"doing some thing: %f", [UIApplication sharedApplication].backgroundTimeRemaining);
}
- (void)applyForMoreTime {
if ([UIApplication sharedApplication].backgroundTimeRemaining < 30) {
self.backgroundTaskIdentifier = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{
[[UIApplication sharedApplication] endBackgroundTask:self.backgroundTaskIdentifier];
self.backgroundTaskIdentifier = UIBackgroundTaskInvalid;
[self applyForMoreTime];
}];
NSString *filePath = [[NSBundle mainBundle] pathForResource:@"Silence" ofType:@"wav"];
NSURL *fileURL = [[NSURL alloc] initFileURLWithPath:filePath];
if (!fileURL) {
NSLog(@"playEmptyAudio 找不到播放文件");
}
NSError *error = nil;
if (@available(iOS 11.0, *)) {
[[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback mode:AVAudioSessionModeDefault routeSharingPolicy:AVAudioSessionRouteSharingPolicyDefault options:AVAudioSessionCategoryOptionMixWithOthers error:&error];
} else {
// Fallback on earlier versions
[[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback mode:AVAudioSessionModeDefault options:AVAudioSessionCategoryOptionMixWithOthers error:&error];
}
// 0.0~1.0,默认为1.0
self.audioPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:fileURL error:&error];
[self.audioEngine reset];
[self.audioPlayer play];
[self.audioPlayer stop];
}
}
@end
参考链接：
https://www.jianshu.com/p/311d49195d86
