AVAudioPlayer do not play AMR files

I ad using below code to download an AMR file from web and playing by AVAudioPlayer but all times I get the unrecongnize selector sent to instance error.

This is the method that start download and play:

- (IBAction)DisplayAudioPlayView:(id)sender 
{    
    [self InitializePlayer];   
}

-(void) InitializePlayer
{
    // Get the file path to the doa audio to play.
    NSString *filePath = [[ServerInteraction instance] getAudio:audioData.ID];

    // Convert the file path to a URL.
    NSURL *fileURL = [[NSURL alloc] initFileURLWithPath: filePath];

    //Initialize the AVAudioPlayer.
    audioPlayer=  [AVPlayer playerWithURL:fileURL] ;
    audioPlayer.delegate= self; //THIS LINE CAUSE ERROR//

    // Preloads the buffer and prepares the audio for playing.
    [audioPlayer prepareToPlay];
    audioPlayer.currentTime = 0;

    [audioPlayer play]
}

Edit

Based on @Michael advise I change my code and this post I changed my code to this:

NSURL *fileURL = [[NSURL alloc] initWithString: @"http://www.domain1.com/mysound.mp3"];

//Initialize the AVAudioPlayer.
audioPlayer=  [AVPlayer playerWithURL:fileURL];
[audioPlayer play];

Now it played the sound but when I use http://maindomain.com/mysound.amr it is not playing the sound.

Solution

Check the following points:

AMR is no longer supported (for ≥ iOS 4.3, see supported audio formats in the Apple iOS SDK Documentation).
Do you want to use the AVPlayer (audio and video) or do you want audio only? Use for Audio only the AVAudioPlayer. The following code snippet shows how to handle it.
If you want to use AVAudioPlayer, does your self instance implement the AVAudioPlayerDelegate Protocol?
Does your self instance implement the AVAudioPlayerDelegate Protocol?

Have you added and linked correctly the AVAudioFoundation framework (#import <AVFoundation/AVFoundation.h>)?

- (void)viewDidLoad
{
    [super viewDidLoad];
    NSURL *url = [NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:@"audio" ofType:@"m4a"]];

    NSError *error = noErr;
    self.audioPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:url error:&error];
    if (error)
    {
        NSLog(@"Error in audioPlayer: %@", [error localizedDescription]);
    }
    else 
    {
        self.audioPlayer.delegate = self;
        [self.audioPlayer prepareToPlay];
    }
}

- (void)playAudio
{
    [self.audioPlayer play];
}