在avaudioplayer中播放完声音后执行操作?

我正在使用avaudioplayer框架,我有几个声音一次播放一个。当声音播放完后,我希望应用程序做一些事情。我试着用audioplayerdifinishplaying在第一个声音结束时做这个动作,但是我不能用它来播放第二个声音,因为我有一个重新定义错误。我可以用nstimeinterval来获取声音的持续时间吗?

//  ViewController.h
#import <UIKit/UIKit.h>
#import <AVFoundation/AVFoundation.h>
#import <AVFoundation/AVAudioPlayer.h>

@interface ViewController : UIViewController {  
UIButton        *begin;
UIWindow        *firstTestWindow;
UIWindow        *secondTestWindow;
AVAudioPlayer   *player;
NSTimeInterval  duration;
}  

@property (nonatomic, retain) IBOutlet UIButton     *begin;
@property (nonatomic, retain) IBOutlet UIWindow     *firstTestWindow;
@property (nonatomic, retain) IBOutlet UIWindow     *secondTestWindow;
@property (nonatomic, retain)         AVAudioPlayer   *player;
@property (readonly)                   NSTimeInterval  duration;


- (IBAction)begin:(id)sender;
- (IBAction)doTapScreen:(id)sender;

@end



//ViewController.m
#import "ViewController.h"

@implementation ViewController

@synthesize begin, player, firstTestWindow, secondTestWindow;

//first sound
- (IBAction)begin:(id)sender; {

    [firstTestWindow makeKeyAndVisible];
    NSString *soundFilePath =
    [[NSBundle mainBundle] pathForResource: @"Tone1"
                                    ofType: @"mp3"];

    NSURL *fileURL = [[NSURL alloc] initFileURLWithPath: soundFilePath];

    AVAudioPlayer *newPlayer =
    [[AVAudioPlayer alloc] initWithContentsOfURL: fileURL
                                           error: nil];
    [fileURL release];
    self.player = newPlayer;
    [newPlayer release];

    [player prepareToPlay];
    [self.player play];

}

//If user does not do anything by the end of the sound go to secondWindow
- (void) audioPlayerDidFinishPlaying: (AVAudioPlayer *) player
                    successfully: (BOOL) flag {
                               if (flag==YES) {
    [secondWindow makeKeyAndVisible];
    }
}

//second sound
- (IBAction)doTapScreen:(id)sender {
    //When user touches the screen, either play the sound or go to the next window
    if (self.player.playing) {
    [self.player stop];
    [thirdWindow makeKeyAndVisible];
    }

    else {
    NSString *soundFilePath =
    [[NSBundle mainBundle] pathForResource: @"Tone2"
                ofType: @"mp3"];

    NSURL *fileURL = [[NSURL alloc] initFileURLWithPath: soundFilePath];

    AVAudioPlayer *newPlayer =
    [[AVAudioPlayer alloc] initWithContentsOfURL: fileURL
                                           error: nil];
    [fileURL release];
    self.player = newPlayer;
    [newPlayer release];

    [player prepareToPlay];
    [self.player play];

}
}