IOS-Swift开发基础——后台下载

使用Alamofire下载某文件：

// download to default path
let destination = Alamofire.Request.suggestedDownloadDestination()
let url = "http://7xi8t0.com2.z0.glb.clouddn.com/o_1ah8n9j7c1ltmo7g1hpn3asi9m.apk"
Alamofire.download(.GET, url, destination: destination).progress { (bytes, totalBytes, totalBytesExpected) in
    print(bytes, totalBytes, totalBytesExpected)
    let percent: Float = Float(totalBytes) / Float(totalBytesExpected)
    print(">> ", percent)
    dispatch_async(dispatch_get_main_queue(), {
        self.downloadProgress.progress = percent
    });
}.response { (request, response, _, error) in
    if let error = error {
        print("Error:", error)
        self.sendLocalNotification("Download Error!")
    } else {
        print("Success:", response)
        self.sendLocalNotification("Download Success!")
    }
}

正常程序进入后台后，会在几秒内停止工作；要想申请更长的时间，（最长10分钟），需要用到beginBackgroundTaskWithExpirationHandler/endBackgroundTask

AppDelegate中添加：

var backgroundTask: UIBackgroundTaskIdentifier!

func applicationDidEnterBackground(application: UIApplication) {
        
    if self.backgroundTask != nil {
        application.endBackgroundTask(self.backgroundTask)
        self.backgroundTask = UIBackgroundTaskInvalid
    }
    
    application.beginBackgroundTaskWithExpirationHandler { 
        application.endBackgroundTask(self.backgroundTask)
        self.backgroundTask = UIBackgroundTaskInvalid
    }
}

具体代码：github