如何在不阻止我的iphone应用程序中的用户界面的情况下运行流程

我正在访问iphone上的照片库，导入我在我的应用程序中选择的图片需要很长时间，如何在辅助线程上运行该进程，或者我使用什么解决方案来阻止用户界面？

Answer 1

我在这里使用performSelectOnBackground或GCD对示例代码做了完整的解释：

GCD，线程，程序流和UI更新

这是该post的示例代码部分（减去他的具体问题：

performSelectorInBackground示例：

在这个片段中，我有一个调用长时间运行工作的按钮，一个状态标签，我添加了一个滑块，以显示我可以在bg工作完成时移动滑块。

// on click of button - (IBAction)doWork:(id)sender { [[self feedbackLabel] setText:@"Working ..."]; [[self doWorkButton] setEnabled:NO]; [self performSelectorInBackground:@selector(performLongRunningWork:) withObject:nil]; } - (void)performLongRunningWork:(id)obj { // simulate 5 seconds of work // I added a slider to the form - I can slide it back and forth during the 5 sec. sleep(5); [self performSelectorOnMainThread:@selector(workDone:) withObject:nil waitUntilDone:YES]; } - (void)workDone:(id)obj { [[self feedbackLabel] setText:@"Done ..."]; [[self doWorkButton] setEnabled:YES]; } 

GCD示例：

 // on click of button - (IBAction)doWork:(id)sender { [[self feedbackLabel] setText:@"Working ..."]; [[self doWorkButton] setEnabled:NO]; // async queue for bg work // main queue for updating ui on main thread dispatch_queue_t queue = dispatch_queue_create("com.sample", 0); dispatch_queue_t main = dispatch_get_main_queue(); // do the long running work in bg async queue // within that, call to update UI on main thread. dispatch_async(queue, ^{ [self performLongRunningWork]; dispatch_async(main, ^{ [self workDone]; }); }); } - (void)performLongRunningWork { // simulate 5 seconds of work // I added a slider to the form - I can slide it back and forth during the 5 sec. sleep(5); } - (void)workDone { [[self feedbackLabel] setText:@"Done ..."]; [[self doWorkButton] setEnabled:YES]; } 

Answer 2

使用异步连接。 它不会阻止UI在后面进行提取时。

当我不得不下载图像时， 这对我帮助很大。

Answer 3

一个选项是使用performSelectorInBackground:withObject: