前言
一般APP在按下Home键被挂起后，这时APP的 backgroundTimeRemaining 也就是后台运行时间大约只有3分钟，如果在退出APP后，过十几二十二分钟或者更长时间再回到APP，APP就会回到刚打开时的状态，也就是首页；有的项目在被挂起后需要在后台运行一段时间，使有足够的时间来完成与服务器对接的操作，或者需要一直运行的需求；如果需要，则在APP被挂起后，申请后台，来延长后台运行时间。
APP申请后台运行的方式有几种：
播放音乐
定位
Newsstand downloads
fetch 等；
这里主要说下后台播放无声音乐（其实是不播放），采用哪种方式，对应勾选上图；我的项目中有音频播放需求，如果没有，那就找一个播放音频的理由，或者用其他方式实现。
实现
这里采用了两个单例：电话监控（XKTelManager）、后台运行（XKBGRunManager），电话监控可以忽略，视情况而用；采用单例是为了方便管理；
XKTelManager.h
#import <Foundation/Foundation.h>
@interface XKTelManager : NSObject
///是否在后台运行
@property (nonatomic,assign) BOOL inBackgroundRun;
+ (XKTelManager *)sharedManager;
- (void)startMonitor;
@end
XKTelManager.m
#import "XKTelManager.h"
#import "XKBGRunManager.h"
#import <CoreTelephony/CTCallCenter.h>
#import <CoreTelephony/CTCall.h>
static XKTelManager *_sharedManger;
@interface XKTelManager()
@property (nonatomic, strong) CTCallCenter *callCenter;
@end
@implementation XKTelManager
+ (XKTelManager *)sharedManager{
static dispatch_once_t onceTelSingle;
dispatch_once(&onceTelSingle, ^{
if (!_sharedManger) {
_sharedManger = [[XKTelManager alloc]init];
}
});
return _sharedManger;
}
- (instancetype)init{
self = [super init];
if (self) {
_inBackgroundRun = NO;
}
return self;
}
#pragma mark -********* 监听电话相关
- (void)startMonitor {
__weak typeof(self) weakSelf = self;
_callCenter = [[CTCallCenter alloc] init];
_callCenter.callEventHandler = ^(CTCall * call) {
///如果已经进入后台了，不做任何操作
if (weakSelf.inBackgroundRun) {
return;
}
///APP未进入后台
if ([call.callState isEqualToString:CTCallStateDisconnected]){
NSLog(@"电话 --- 断开连接");
[[XKBGRunManager sharedManager] stopBGRun];
}
else if ([call.callState isEqualToString:CTCallStateConnected]){
NSLog(@"电话 --- 接通");
}
else if ([call.callState isEqualToString:CTCallStateIncoming]){
NSLog(@"电话 --- 待接通");
[[XKBGRunManager sharedManager] startBGRun];
}
else if ([call.callState isEqualToString:CTCallStateDialing]){
NSLog(@"电话 --- 拨号中");
[[XKBGRunManager sharedManager] startBGRun];
}
else {
NSLog(@"电话 --- 无操作");
}
};
}
@end
XKBGRunManager.h
#import <Foundation/Foundation.h>
@interface XKBGRunManager : NSObject
+ (XKBGRunManager *)sharedManager;
- (void)startBGRun;
- (void)stopBGRun;
@endXKBGRunManager.m
#import "XKBGRunManager.h"
///循环时间
static NSInteger _circulaDuration = 60;
static XKBGRunManager *_sharedManger;
@interface XKBGRunManager()
@property (nonatomic,assign) UIBackgroundTaskIdentifier task;
///后台播放
@property (nonatomic,strong) AVAudioPlayer *playerBack;
@property (nonatomic, strong) NSTimer *timerAD;
///用来打印测试
@property (nonatomic, strong) NSTimer *timerLog;
@property (nonatomic,assign) NSInteger count;
@end
@implementation XKBGRunManager{
CFRunLoopRef _runloopRef;
dispatch_queue_t _queue;
}
+ (XKBGRunManager *)sharedManager{
static dispatch_once_t onceRunSingle;
dispatch_once(&onceRunSingle, ^{
if (!_sharedManger) {
_sharedManger = [[XKBGRunManager alloc]init];
}
});
return _sharedManger;
}
/// 重写init方法，初始化音乐文件
- (instancetype)init {
if (self = [super init]) {
[self setupAudioSession];
_queue = dispatch_queue_create("com.audio.inBackground", NULL);
//静音文件
NSString *filePath = [[NSBundle mainBundle] pathForResource:@"****" ofType:@"mp3"];
NSURL *fileURL = [[NSURL alloc] initFileURLWithPath:filePath];
self.playerBack = [[AVAudioPlayer alloc] initWithContentsOfURL:fileURL error:nil];
[self.playerBack prepareToPlay];
// 0.0~1.0,默认为1.0
self.playerBack.volume = 0.01;
// 循环播放
self.playerBack.numberOfLoops = -1;
}
return self;
}
- (void)setupAudioSession {
// 新建AudioSession会话
AVAudioSession *audioSession = [AVAudioSession sharedInstance];
// 设置后台播放
NSError *error = nil;
[audioSession setCategory:AVAudioSessionCategoryPlayback withOptions:AVAudioSessionCategoryOptionMixWithOthers error:&error];
if (error) {
NSLog(@"Error setCategory AVAudioSession: %@", error);
}
NSLog(@"%d", audioSession.isOtherAudioPlaying);
NSError *activeSetError = nil;
// 启动AudioSession，如果一个前台app正在播放音频则可能会启动失败
[audioSession setActive:YES error:&activeSetError];
if (activeSetError) {
NSLog(@"Error activating AVAudioSession: %@", activeSetError);
}
}
- (void)startBGRun{
[self.playerBack play];
[self applyforBackgroundTask];
///确保两个定时器同时进行
dispatch_async(_queue, ^{
self.timerLog = [[NSTimer alloc] initWithFireDate:[NSDate date] interval:1 target:self selector:@selector(log) userInfo:nil repeats:YES];
self.timerAD = [[NSTimer alloc] initWithFireDate:[NSDate date] interval:_circulaDuration target:self selector:@selector(startAudioPlay) userInfo:nil repeats:YES];
_runloopRef = CFRunLoopGetCurrent();
[[NSRunLoop currentRunLoop] addTimer:self.timerAD forMode:NSDefaultRunLoopMode];
[[NSRunLoop currentRunLoop] addTimer:self.timerLog forMode:NSDefaultRunLoopMode];
CFRunLoopRun();
});
}
- (void)applyforBackgroundTask{
_task =[[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{
dispatch_async(dispatch_get_main_queue(), ^{
[[UIApplication sharedApplication] endBackgroundTask:_task];
_task = UIBackgroundTaskInvalid;
});
}];
}
- (void)log{
_count = _count + 1;
NSLog(@"_count = %ld",_count)
}
- (void)startAudioPlay{
_count = 0;
dispatch_async(dispatch_get_main_queue(), ^{
if ([[UIApplication sharedApplication] backgroundTimeRemaining] < 61.0) {
NSLog(@"后台快被杀死了");
[self.playerBack play];
[self applyforBackgroundTask];
}
else{
NSLog(@"后台继续活跃呢");
}///再次执行播放器停止，后台一直不会播放音乐文件
[self.playerBack stop];
});
}
- (void)stopBGRun{
if (self.timerAD) {
CFRunLoopStop(_runloopRef);
[self.timerLog invalidate];
self.timerLog = nil;
// 关闭定时器即可
[self.timerAD invalidate];
self.timerAD = nil;
[self.playerBack stop];
}
if (_task) {
[[UIApplication sharedApplication] endBackgroundTask:_task];
_task = UIBackgroundTaskInvalid;
}
}
@end最后在 AppDelegate.m 对应的方法中，实现开启和停止后台运行即可！
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持编程网。
