fast-app-switching | 易学教程

UIApplication openURL background

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问题 In my iOS 4 application, I need to open a URL from the background, at a time specified from the user. However, for some reason, I cannot launch a URL from the background for some reason. Here is my code for opening a URL: if (![[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"http://www.stackoverflow.com"]]) { // the URL wasn't opened. we will ignore this for now. } That code is all being launched from a daemon thread created earlier. I have tested this code on the simulator,

Why should we copy blocks rather than retain?

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问题 I recently met a problem using blocks with Facebook's app switching. I needed to call a block after the Facebook login. First my block was destroyed when the app switched back ('cause it was on the stack), so I decided to retain it. But that didn't work, and I messed with that problem :/. I found a solution on that blog and also here. My question is simply : why copy works and retain does not ? 回答1: Because when you create a block there is nothing to retain, since it doesn't exist in the heap

Grey GPS arrow shown in statusbar although location based application killed using Fast App Switcher

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I am writing a location based application for iOS 5. The application is using the CLLocationManager to receive Location updates. When the application is started I am creating the LocationManager, calling [self.locationManager startUpdatingLocation]; and the grey location arrow appears in the statusbar. When the application enters background I am calling [self.locationManager stopUpdatingLocation]; [self.locationManager startMonitoringSignificantLocationChanges]; cause I just want to receive significant location changes while the app is in background. The grey location arrow is still shown. I

UIApplication openURL background

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In my iOS 4 application, I need to open a URL from the background, at a time specified from the user. However, for some reason, I cannot launch a URL from the background for some reason. Here is my code for opening a URL: if (![[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"http://www.stackoverflow.com"]]) { // the URL wasn't opened. we will ignore this for now. } That code is all being launched from a daemon thread created earlier. I have tested this code on the simulator, and the URL is not opened, and the method returns YES for some reason, but when I open my application