Playing a Sound, Waiting it to Finish Playing and Continuing (iPhone)

Introduction

As a beginner with iPhone development in Objective-C, playing a sound is an essential feature that can be achieved using the SystemSound API. In this article, we will explore how to play a sound, wait for it to finish playing, and continue with the rest of the code.

Understanding System Sound API

The SystemSound API provides a way to play sounds on the device. The AudioServicesCreateSystemSoundID function is used to create a system sound ID, which is then used to play the sound using the AudioServicesPlaySystemSound function.

In our case, we need to play a sound file named “file.wav”. We will use the SystemSound API to achieve this.

Breaking Down the Code

The provided answer breaks down the solution into two main functions: playASound: and startSound.

1. playASound:

This function takes a filename as input, creates a system sound ID using AudioServicesCreateSystemSoundID, and plays the sound using AudioServicesPlaySystemSound. The function returns the created system sound ID.

-(SystemSoundID) playASound: (NSString *) file {
    // Get the filename of the sound file:
    NSString *path = [NSString stringWithFormat:@"%@/%@",
                      [[NSBundle mainBundle] resourcePath],
                      file];

    SystemSoundID soundID;
    // Get a URL for the sound file
    NSURL *filePath = [NSURL fileURLWithPath:path isDirectory:NO];
    AudioServicesCreateSystemSoundID((CFURLRef)filePath, &soundID);
    // Play the file
    AudioServicesPlaySystemSound(soundID);
    return soundID;
}

2. startSound:

This function calls playASound: and prints “Hello” immediately after playing the sound. It also adds a completion handler to register a callback function when the sound finishes playing.

-(void)startSound
{
   printf("Hello");
    SystemSoundID id = [self playASound:@"file.wav"];
    AudioServicesAddSystemSoundCompletion (
       id,
       NULL,
       NULL,
       endSound,
       NULL
   );
}

3. endSound:

This function is the callback registered when the sound finishes playing. It prints “World” and returns.

void endSound (
   SystemSoundID  ssID,
   void           *clientData
)
{
   printf("world\n");
}

Putting it all Together

To wait for the sound to finish playing, we need to add a completion handler to AudioServicesAddSystemSoundCompletion. This completion handler is called when the sound finishes playing.

-(void)startSound
{
   printf("Hello");
    SystemSoundID id = [self playASound:@"file.wav"];
    AudioServicesAddSystemSoundCompletion (
       id,
       NULL,
       NULL,
       endSound,
       NULL
   );
}

In this code, endSound is the callback function that is called when the sound finishes playing. It prints “World” and returns.

Conclusion

Playing a sound on an iPhone using Objective-C can be achieved by creating a system sound ID using AudioServicesCreateSystemSoundID and playing the sound using AudioServicesPlaySystemSound. To wait for the sound to finish playing, we need to add a completion handler to AudioServicesAddSystemSoundCompletion.

By breaking down the solution into smaller functions and registering a callback function, we can ensure that our code is efficient and effective.

Tips and Variations

• When working with system sounds, make sure to handle any potential errors that may occur during playback.
• To play multiple sounds simultaneously, you can use AudioServicesAddSystemSoundCompletion multiple times with different sound IDs.
• You can also use other audio APIs such as AVAudioPlayer or AVAudioSession to play sounds on your iPhone app.

Example Use Cases

• Playing a sound effect in a game to signal a successful action.
• Playing a sound alert when the user receives an incoming message.
• Playing a music track during a transition between screens.

Last modified on 2024-10-30