multitasking

问题 I have MPMoviePlayerController that should play video's audio in background and should be controlled by the multitasking play/pause controls. After updating .plist file with Required background modes and calling the following: - (void)startBackgroundStreaming { [[UIApplication sharedApplication] beginReceivingRemoteControlEvents]; [self becomeFirstResponder]; NSError *activationError = nil; AVAudioSession *audioSession = [AVAudioSession sharedInstance]; [audioSession setCategory

问题 I read that Linux kernel is preemptive, which is different from most Unix kernels. So, what does it really mean for a kernal to be preemptive? Some analogies or examples would be better than pure theoretical explanation. ADD 1 -- 11:00 AM 12/7/2018 Preemptive is just one paradigm of multi-tasking. There are others like Cooperative Multi-tasking. A better understanding can be achieved by comparing them. 回答1: Imagine the simple view of preemptive multi-tasking. We have two user tasks, both of

问题 I'm trying to play sequence of audio files in the background using AVAudioPlayer. When the app is not in the background it plays well, but when the app goes to the background it won't play the second song. Here is my code: -(void)playAudio:(NSString *)path{ NSURL *url = [NSURL fileURLWithPath:path]; NSError *error; AVAudioPlayer *ap = [[AVAudioPlayer alloc] initWithContentsOfURL:url error:&error]; [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback error:nil]; [

问题 I was just wondering if it was possible to make an iOS app that would track your location via GPS while it was in the background. I tried this with the built-in app "Maps", but to no avail. If this is possible, it would be great if you could refer me to some sample code, documentations, or tutorials! (if this is a duplicate, please let me know and I will remove it) 回答1: This is possible — see this document for multitasking in general and this section of the Location Awareness Programming

问题 I have added the UIBackgroundModes property in Info.plist to have an array entry of " audio " and have added the call to setup the audio session: [session setCategory: AVAudioSessionCategoryPlayback error: &error]; . However, the only test device I have is the iPod Touch 2G which doesn't support multitasking. I've tried the simulator but the music stops playing when I switch to Safari. But when I switch back to my app, the song continues playing to a farther location than when I left the app.

问题 I have added the UIBackgroundModes property in Info.plist to have an array entry of " audio " and have added the call to setup the audio session: [session setCategory: AVAudioSessionCategoryPlayback error: &error]; . However, the only test device I have is the iPod Touch 2G which doesn't support multitasking. I've tried the simulator but the music stops playing when I switch to Safari. But when I switch back to my app, the song continues playing to a farther location than when I left the app.

问题 How many goroutines can I use painless? For example wikipedia says, in Erlang 20 million processes can be created without degrading performance. Update: I've just investigated in goroutines performance a little and got such a results: It looks like goroutine lifetime is more then calculating sqrt() 1000 times ( ~45µs for me ), the only limitation is memory Goroutine costs 4 — 4.5 KB 回答1: If a goroutine is blocked, there is no cost involved other than: memory usage slower garbage-collection

问题 Recently when being interviewed, I got this question. Q: Have you written multithreaded applications? A: Yes Q: Care to explain more? A: I used Tasks (Task Parallel library) to carry out some tasks like waiting for some info from internet while loading UI . This improves my application usability. Q: But, just you have used TPL means that you have written an multithreaded application? Me: (Not sure what to say1) So, whats exactly a multi-threaded application? Is it different from using Tasks ?

问题 Given this Unix shell script: test.sh: #!/bin/sh sleep 2 & sleep 5 & sleep 1 & wait time ./test.sh real 0m5.008s user 0m0.040s sys 0m0.000s How would you accomplish the same thing in Ruby on a Unix machine? The sleep commands are just an example, just assume that they are long running external commands instead. 回答1: Straight from Process#waitall documentation: fork { sleep 0.2; exit 2 } #=> 27432 fork { sleep 0.1; exit 1 } #=> 27433 fork { exit 0 } #=> 27434 p Process.waitall Of course,

问题 I wanted to cancel the method, to request a confirmation from the user when he presses the button "HOME" where on iPhone would go into the execution in background. If the user accepts, enters into the execution in background, if not accept, I do not do anything. I looked in the FORUM, in the documentation from Apple and I found nothing. Could anyone help me? Thanks in advance! 回答1: No you can't override this. The event will always fire but it does give you time to clean up before you move to