用MPMediaPickerController拾取音频

Question

嗨，我正在使用MPMediaPickerController从电话库中选择音频文件。但它给了我空白的屏幕。我不明白为什么会这样。我在模拟器上运行应用程序。这是我的代码

- (IBAction)selectFile:(UIButton *)sender{

MPMediaPickerController *mediaPicker = [[MPMediaPickerController alloc] initWithMediaTypes: MPMediaTypeMusic];
mediaPicker.delegate = self;
mediaPicker.allowsPickingMultipleItems = YES;
mediaPicker.prompt = @"Select Your Favourite Song!";
[mediaPicker loadView];
[self.navigationController presentViewController:mediaPicker animated:YES completion:nil]; }

Answer 1

MPMediaPickerController在模拟器中不工作。苹果在“”下的"iPod图书馆访问编程指南“中注意到了这一点。便条上写着：

注意:要遵循这些步骤，您将需要一个配置设备，因为模拟器无法访问设备的iPod库。

为了防止断言，您可以始终检查是否可以在代码中访问此操作(下面的代码使用了ARCASDK5.0)。

MPMediaPickerController *picker = [[MPMediaPickerController alloc]     initWithMediaTypes:MPMediaTypeAnyAudio];

[picker setDelegate:self];
[picker setAllowsPickingMultipleItems:YES];
[picker setPrompt:NSLocalizedString(@"Add songs to play","Prompt in media item picker")];

@try {
[picker loadView]; // Will throw an exception in iOS simulator
[self presentViewController:picker animated:YES completion:nil];
}
@catch (NSException *exception) {
    [[[UIAlertView alloc] initWithTitle:NSLocalizedString(@"Oops!",@"Error title")
                            message:NSLocalizedString(@"The music library is not available.",@"Error message when MPMediaPickerController fails to load") 
                           delegate:nil 
                  cancelButtonTitle:@"OK" 
                  otherButtonTitles:nil] show];
}

Answer 2

对于那些想在Swift中找到答案的人来说：

@IBAction func openMediaPickerController(sender: AnyObject) {
        let picker = MPMediaPickerController()
        picker.delegate = self
        picker.allowsPickingMultipleItems = true
        picker.prompt = NSLocalizedString("Chose audio file", comment: "Please chose an audio file")
        self.presentViewController(picker, animated: true, completion: nil)
}
func mediaPickerDidCancel(mediaPicker: MPMediaPickerController) {
    self.dismissViewControllerAnimated(true, completion: nil)
}
func mediaPicker(mediaPicker: MPMediaPickerController, didPickMediaItems mediaItemCollection: MPMediaItemCollection) {
    //run any code you want once the user has picked their chosen audio
}