iOS開發(fā)基礎(chǔ)102-后臺(tái)保活方案

iOS系統(tǒng)在后臺(tái)執(zhí)行程序時(shí)，有嚴(yán)格的限制，為了更好地管理資源和電池壽命，iOS會(huì)限制應(yīng)用程序在后臺(tái)的運(yùn)行時(shí)間。然而，iOS提供了一些特定的策略和技術(shù)，使得應(yīng)用程序可以在特定場(chǎng)景下保持后臺(tái)運(yùn)行（即“后臺(tái)保活”）。以下是iOS中幾種常見的后臺(tái)保活方案，并附上示例代碼：

一、后臺(tái)任務(wù)

利用beginBackgroundTask和endBackgroundTask來執(zhí)行后臺(tái)任務(wù)。后臺(tái)任務(wù)將在應(yīng)用程序進(jìn)入后臺(tái)時(shí)仍能保持有限的時(shí)間執(zhí)行任務(wù)。

#import <UIKit/UIKit.h>

@interface AppDelegate : UIResponder <UIApplicationDelegate>

@property (strong, nonatomic) UIWindow *window;
@property (assign, nonatomic) UIBackgroundTaskIdentifier bgTask;

@end

@implementation AppDelegate

- (void)applicationDidEnterBackground:(UIApplication *)application {
    self.bgTask = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{
        [[UIApplication sharedApplication] endBackgroundTask:self.bgTask];
        self.bgTask = UIBackgroundTaskInvalid;
    }];
    
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        // 在這里執(zhí)行你的后臺(tái)任務(wù)
        for (int i = 0; i < 100; i++) {
            NSLog(@"Background task running %d", i);
            [NSThread sleepForTimeInterval:1];
        }
        
        [[UIApplication sharedApplication] endBackgroundTask:self.bgTask];
        self.bgTask = UIBackgroundTaskInvalid;
    });
}

@end

二、使用Background Fetch

利用Background Fetch，系統(tǒng)會(huì)間歇性地喚醒應(yīng)用程序，以便它可以執(zhí)行任務(wù)或獲取數(shù)據(jù)。需要在Xcode的“Capabilities”中開啟Background Modes，并勾選“Background fetch”。

#import <UIKit/UIKit.h>

@interface AppDelegate : UIResponder <UIApplicationDelegate>

@property (strong, nonatomic) UIWindow *window;

@end

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    [application setMinimumBackgroundFetchInterval:UIApplicationBackgroundFetchIntervalMinimum];
    return YES;
}

- (void)application:(UIApplication *)application performFetchWithCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler {
    // 在這里執(zhí)行你的后臺(tái)數(shù)據(jù)獲取任務(wù)
    NSLog(@"Background fetch started");

    // 模擬數(shù)據(jù)獲取
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(5 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
        NSLog(@"Background fetch completed");
        completionHandler(UIBackgroundFetchResultNewData);
    });
}

@end

三、使用遠(yuǎn)程通知（Silent Push Notification）

利用遠(yuǎn)程通知，在接收到通知時(shí)，系統(tǒng)會(huì)喚醒應(yīng)用程序執(zhí)行指定的任務(wù)。需要開啟Remote notifications，在Application Capabilities中勾選“Remote notifications”。

#import <UIKit/UIKit.h>
#import <UserNotifications/UserNotifications.h>

@interface AppDelegate : UIResponder <UIApplicationDelegate, UNUserNotificationCenterDelegate>

@property (strong, nonatomic) UIWindow *window;

@end

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    [UNUserNotificationCenter currentNotificationCenter].delegate = self;
    [[UNUserNotificationCenter currentNotificationCenter] requestAuthorizationWithOptions:(UNAuthorizationOptionAlert | UNAuthorizationOptionSound | UNAuthorizationOptionBadge) completionHandler:^(BOOL granted, NSError * _Nullable error) {
        if (granted) {
            [[UIApplication sharedApplication] registerForRemoteNotifications];
        }
    }];
    return YES;
}

- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo fetchCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler {
    // 在這里處理收到的遠(yuǎn)程通知
    NSLog(@"Received remote notification");

    // 模擬處理任務(wù)
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(5 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
        NSLog(@"Handled remote notification");
        completionHandler(UIBackgroundFetchResultNewData);
    });
}

@end

四、使用特定的后臺(tái)模式（Background Modes）

iOS提供了一些特定的后臺(tái)模式，允許程序在后臺(tái)持續(xù)運(yùn)行。常見的后臺(tái)模式包括：

Audio: 允許應(yīng)用程序在后臺(tái)播放音頻。
Location: 允許應(yīng)用程序在后臺(tái)持續(xù)獲取位置更新。
VoIP: 允許應(yīng)用程序在后臺(tái)偵聽VoIP事件。
Bluetooth: 允許應(yīng)用程序與藍(lán)牙設(shè)備通信。

1. Audio后臺(tái)模式

需要在Xcode的“Capabilities”中開啟Background Modes，并勾選“Audio, AirPlay, and Picture in Picture”。

#import <AVFoundation/AVFoundation.h>

@interface AppDelegate ()

@property (nonatomic, strong) AVAudioPlayer *audioPlayer;

@end

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    NSError *error = nil;
    NSURL *audioURL = [[NSBundle mainBundle] URLForResource:@"audioFileName" withExtension:@"mp3"];
    self.audioPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:audioURL error:&error];
    [self.audioPlayer prepareToPlay];
    
    AVAudioSession *audioSession = [AVAudioSession sharedInstance];
    [audioSession setCategory:AVAudioSessionCategoryPlayback error:&error];
    [audioSession setActive:YES error:&error];
    
    return YES;
}

- (void)applicationDidEnterBackground:(UIApplication *)application {
    [self.audioPlayer play];
}

@end

2. Location后臺(tái)模式

需要在Xcode的“Capabilities”中開啟Background Modes，并勾選“Location updates”。

#import <CoreLocation/CoreLocation.h>

@interface AppDelegate () <CLLocationManagerDelegate>

@property (nonatomic, strong) CLLocationManager *locationManager;

@end

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    self.locationManager = [[CLLocationManager alloc] init];
    self.locationManager.delegate = self;
    [self.locationManager requestAlwaysAuthorization];
    return YES;
}

- (void)applicationDidEnterBackground:(UIApplication *)application {
    self.locationManager.desiredAccuracy = kCLLocationAccuracyBest;
    [self.locationManager startUpdatingLocation];
}

- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray<CLLocation *> *)locations {
    CLLocation *location = [locations lastObject];
    NSLog(@"Background location: %@", location);
}

@end

五、使用后臺(tái)URLSession

使用NSURLSession來執(zhí)行后臺(tái)下載和上傳任務(wù)。需要在后臺(tái)配置中開啟Background Modes，并勾選“Background fetch”和“Remote notifications”。

#import <UIKit/UIKit.h>

@interface AppDelegate : UIResponder <UIApplicationDelegate, NSURLSessionDelegate, NSURLSessionDownloadDelegate>

@property (strong, nonatomic) UIWindow *window;
@property (nonatomic, strong) NSURLSession *backgroundSession;

@end

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    NSURLSessionConfiguration *config = [NSURLSessionConfiguration backgroundSessionConfigurationWithIdentifier:@"com.example.background"];
    self.backgroundSession = [NSURLSession sessionWithConfiguration:config delegate:self delegateQueue:nil];
    return YES;
}

- (void)applicationDidEnterBackground:(UIApplication *)application {
    NSURL *url = [NSURL URLWithString:@"http://example.com/largefile.zip"];
    NSURLSessionDownloadTask *downloadTask = [self.backgroundSession downloadTaskWithURL:url];
    [downloadTask resume];
}

- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didFinishDownloadingToURL:(NSURL *)location {
    NSLog(@"Download completed: %@", location);
    // 處理下載結(jié)果，比如保存文件
}

@end

通過上述幾種方案，我們可以在iOS應(yīng)用程序中實(shí)現(xiàn)各種場(chǎng)景下的后臺(tái)保活。每種方案都有其適用的場(chǎng)景和限制，開發(fā)者需要根據(jù)應(yīng)用的實(shí)際需求和系統(tǒng)提供的特性，選擇合適的后臺(tái)保活方案。

posted @ 2024-07-16 16:27 Mr.陳閱讀(2546) 評(píng)論(0) 收藏舉報(bào)

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