【发布时间】：2018-07-10 05:21:29
【问题描述】：
我有一个应用程序，它在首次安装时会下载大量数据（主要是图像和文档文件）。目前，我只能在 HUD 中显示进度。但我希望我能以某种方式允许在应用程序进入后台（或设备被锁定）时下载数据。由于该应用程序针对的是运行 iOS 7.0 及更高版本的设备，因此我使用 NSURLSession 下载数据。我已经通过 Stackoverflow 上的各种线程以及教程here。即使按照教程对我的应用程序进行了更改，我的应用程序也不会继续下载。我在 iPad 上进行了测试。当应用程序被发送到后台（或锁定）时，下载会暂停并在应用程序进入前台时恢复。
我不确定我的方法是错误的还是我的实施有缺陷。欢迎任何帮助/建议。
应用程序的流程如下：'LoginViewController'调用内部方法
downloadData，该方法具有执行下载任务的SaveProjectData类的对象。
LoginViewController.m
@implementation LoginViewController
- (void)viewDidLoad {
}
- (IBAction)sumitButtonDidClick:(id)sender {
if ([self checkNetworkConnection] ==NotReachable) {
UIAlertView * alertView=[[UIAlertView alloc] initWithTitle:@"Network Error" message:@"No internet Connection." delegate:nil cancelButtonTitle:@"OK" otherButtonTitles: nil];
[alertView show];
} else {
MBProgressHUD *hud = [MBProgressHUD showHUDAddedTo:self.view animated:YES];
hud.mode = MBProgressHUDModeDeterminateHorizontalBar;
hud.label.text = NSLocalizedString(@"Downloading...", @"HUD loading title");
dispatch_async(dispatch_get_global_queue(QOS_CLASS_USER_INITIATED, 0), ^{
double delayInSeconds = 1.0;
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delayInSeconds * NSEC_PER_SEC));
if ([self loginStatus]) {
NSString * userName = self.user_nameTxtField.text;
CallProjectAPI * callProjectAPIinst = [[CallProjectAPI alloc] init];
NSString * appStatus = [[NSUserDefaults standardUserDefaults] objectForKey:@"appStatus"];
if ([appStatus isEqualToString:@"N"]) {
[callProjectAPIinst dataFromJSONFile];
[callProjectAPIinst saveImageName];
} else {
[self doSomeWorkWithProgress];
[callProjectAPIinst callAPI];
[self doSomeWorkWithProgress];
[self downloadData];
}
hud.label.text = NSLocalizedString(@"Complete!", @"HUD completed title");
porjectVC = [self.storyboard instantiateViewControllerWithIdentifier:@"ProjectViewController"];
dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
[self presentViewController:porjectVC animated:YES completion:nil];
[hud hideAnimated:YES];
});
[[NSUserDefaults standardUserDefaults] setObject:userName forKey:@"userName"];
} else {
dispatch_async(dispatch_get_main_queue(), ^{
[hud hideAnimated:YES];
UIAlertView * alert=[[UIAlertView alloc] initWithTitle:@"Alert" message:@"User Name or Password is wrong." delegate:nil cancelButtonTitle:@"ok" otherButtonTitles:nil];
[alert show];
});
}
});
}
}
-(void)downloadData{
if ([self checkNetworkConnection] ==NotReachable) {
UIAlertView * alertView=[[UIAlertView alloc] initWithTitle:@"Network Error" message:@"No internet Connection." delegate:nil cancelButtonTitle:@"OK" otherButtonTitles: nil];
[alertView show];
} else {
NSString * status =[[NSUserDefaults standardUserDefaults] objectForKey:@"DownloadData"];
if (status == nil) {
SaveProjectData * saveProjectDataInst = [[SaveProjectData alloc] init];
[self doSomeWorkWithProgress];
[saveProjectDataInst saveAboutImage];
[self doSomeWorkWithProgress];
[saveProjectDataInst saveConstructionUpdateImages];
[self doSomeWorkWithProgress];
[saveProjectDataInst saveLogImages];
[saveProjectDataInst saveSmallImages];
[self doSomeWorkWithProgress];
[saveProjectDataInst saveFloorPlanImages];
[self doSomeWorkWithProgress];
[saveProjectDataInst saveUnitPlanImages];
[self doSomeWorkWithProgress];
[saveProjectDataInst saveMasterPlanImages];
[self doSomeWorkWithProgress];
[saveProjectDataInst saveBrochurs];
[self doSomeWorkWithProgress];
[saveProjectDataInst saveGalleryImages];
[self doSomeWorkWithProgress];
[saveProjectDataInst saveAmenitiesImages];
[self doSomeWorkWithProgress];
[saveProjectDataInst saveVideos];
[self doSomeWorkWithProgress];
[saveProjectDataInst saveMapImage];
[self doSomeWorkWithProgress];
[saveProjectDataInst saveBannerImage];
[self doSomeWorkWithProgress];
[saveProjectDataInst savewalkthrough];
[self doSomeWorkWithProgress];
[saveProjectDataInst saveFlatImages];
[self doSomeWorkWithProgress];
[saveProjectDataInst saveEventImages];
[self doSomeWorkWithProgress];
[[NSUserDefaults standardUserDefaults] setObject:@"YES" forKey:@"DownloadData"];
[saveProjectDataInst getUpdatedListForEachProject];
}
}
}
- (void)doSomeWorkWithProgress {
progress += 0.049f;
dispatch_async(dispatch_get_main_queue(), ^{
// Instead we could have also passed a reference to the HUD
// to the HUD to myProgressTask as a method parameter.
[MBProgressHUD HUDForView:self.view].progress = progress;
});
}
@end
另一种方法可能是提供一个按钮，用户单击该按钮并下载数据，同时用户仍然可以继续使用 其他人的设备。关于我如何实现的任何指针 是吗？
【问题讨论】：
-
查看此 (stackoverflow.com/questions/45338412/…) 答案和示例项目。它可能会帮助你。
-
“我可以在应用程序进入后台时以某种方式允许下载数据”这是一个不合逻辑的请求。
-
谢谢@beshio。
-
@ElTomato，请求背后的逻辑是“初始”数据下载量巨大且一次性。因此，用户可以将应用程序设置为下载数据，然后在设备上执行一些其他任务。希望你明白了。
-
这个链接可以帮助你有哪些可能性：raywenderlich.com/143128/…
标签： ios objective-c background-process nsurlsession