IOS React Native: Sound Replays On App Focus Fix

Hey guys! Ever encountered a frustrating bug in your React Native iOS app where sounds replay themselves when the app regains focus? Yeah, it's a real head-scratcher. This issue, specifically when using the react-native-sound library, can disrupt the user experience, making your app feel buggy and unprofessional. Let's dive deep into this problem, explore the root cause, and discuss potential solutions to prevent sound replays when your iOS app gets back into focus.

The Core Problem: React Native Sound Replay

The Problem: The issue is pretty straightforward. You've got a sound playing in your React Native iOS app. You minimize the app, do something else, and then return. Boom! The sound starts playing again, even though it should have finished. This is unexpected behavior because the original sound's playback should be complete. This unexpected sound behavior, triggered when an app transitions back into an active state, has been a persistent nuisance for developers relying on audio cues within their applications. The issue is especially prominent with the react-native-sound library, which is commonly used to incorporate audio playback into React Native projects.

Observed Behavior: The primary symptom is the unwanted replay of sounds whenever the app transitions from the background to the foreground. This can be jarring if the sound is a notification, an effect, or any other type of non-looping audio.

Expected Behavior: The expected behavior is that the sound should only play when explicitly triggered by the application logic, such as a user action or a specific event. The sound should not automatically restart upon the app becoming active again.

Debugging Steps and Troubleshooting

To effectively tackle this iOS React Native sound issue, it's essential to perform the following steps for troubleshooting. First, you should meticulously check your sound initialization and playback logic. Verify whether you're calling .play() at any point when the app regains focus. Check the AppState to determine when the app enters the background or foreground.

Second, test whether the issue happens consistently or sporadically. Test in both simulator and devices. This helps narrow down if the problem is specific to certain devices or iOS versions. Third, examine the react-native-sound library's documentation and any known issues or bugs related to focus handling. Check their GitHub repository to see if there are any existing solutions or workarounds. Fourth, add logging statements at different parts of your code to see if the sound is getting called multiple times.

Finally, inspect your native iOS code. If you are using native iOS modules, carefully review them to see if any of these methods might be responsible. If your sound instance is not being properly released or if the app's lifecycle events are incorrectly triggering sound playback, this could be the source of your problem. By following these steps, you can pinpoint the source of the problem and arrive at the right solution, leading to a much smoother user experience within your app.

Deep Dive into the Code and Bug Reproduction

Let's analyze the provided code snippet to understand what might be causing the React Native sound replay issue in iOS. The code uses react-native-sound to play a sound file (scan.mp3) when a specific condition is met, such as when scanType and scanData?.task_id are both truthy.

import React from 'react'
import { AppState, Dimensions } from 'react-native'
import Sound from 'react-native-sound'
import Toast from 'react-native-toast-message'
import { useDispatch, useSelector } from 'react-redux'

import Actions from '@src/actions'
import $t from '@src/i18n'

Sound.setCategory('Ambient')

const scanSound = new Sound('scan.mp3', Sound.MAIN_BUNDLE, (error) => {
  if (error) {
    console.error('failed to load the sound', error)
  }
})

export const ScanToast: React.FC = () => {
  const dispatch = useDispatch()

  const scanData = useSelector((state) => state?.scan.scanData)
  const scanType = useSelector((state) => state?.scan.scanType)

  React.useEffect(() => {
    if (scanType && scanData?.task_id) {
      scanSound.stop(() => {
        console.log('About to call play') // this is not called when sound is replayed
        scanSound.play()
      })

      if (!scanData.noPopup) {
        // Putting it here as it might change due to rotation
        const screenHeight = Dimensions.get('window').height

        Toast.show({
          type: 'success',
          position: 'top',
          topOffset: screenHeight / 2,
          text1: $t('visits.taskId', { taskId: scanData.task_id }),
          text2: $t(
            'visits.addedSuccessfully',
            {
              type: $t(`visitDetails.${scanType}`).toLowerCase(),
            },
          ),
          autoHide: true,
          visibilityTime: 3000,
          swipeable: false,
        })
      }

      dispatch(Actions.createAction(Actions.SCAN_CLEARED))
    }
  }, [dispatch, scanType, scanData?.task_id])

  return null
}

export default ScanToast

Key points to note:

• Sound Initialization: The scanSound is initialized once when the component mounts. This seems correct. It's using Sound.MAIN_BUNDLE, which is the correct approach to load sounds within your React Native app's main bundle.
• Playback Logic: Inside the useEffect hook, the code checks scanType and scanData?.task_id. If both conditions are met, it attempts to stop and then play the sound. The .stop() method is called first, followed by .play(). This is good, as it ensures that any currently playing sound is stopped before the new one is started. However, the comments suggest that the .play() call is not happening during the app focus. This points to a potential issue.
• AppState and Focus: The code does not explicitly handle AppState changes. Without this, the app may not know when to stop and restart a sound.

Reproduction Steps

To reproduce the bug, you would generally:

1. Trigger the Sound: Ensure that the conditions to play the sound (scanType and scanData?.task_id) are met within the app. The sound should play initially.
2. Minimize the App: Background the app by swiping up from the bottom of the screen or pressing the home button.
3. Return to the App: Bring the app back to the foreground by tapping on its icon from the app switcher or home screen.
4. Observe: The sound will replay automatically, even if it should have finished playing before the app was minimized.

Potential Causes and Root Analysis

So, what's causing this annoying iOS React Native sound replay issue? Here's a breakdown of the probable causes and a deeper root analysis. Several factors can contribute to this problem:

• react-native-sound Library Behavior: The library itself might have a bug. It might not correctly handle the app's lifecycle events, especially when the app moves between the background and foreground states. Sometimes libraries have issues with the sound not being released properly, or being re-initialized automatically.
• iOS Lifecycle Events: iOS manages its app's lifecycle. There are events like applicationWillResignActive, applicationDidEnterBackground, applicationWillEnterForeground, and applicationDidBecomeActive. If the sound playback isn't managed correctly in response to these events, you might see the unwanted replay. If the sound is not stopped during applicationWillResignActive or applicationDidEnterBackground, it might continue to play until the app enters the background state. When the app returns to the foreground, it could incorrectly resume playing the sound.
• Incorrect State Management: If the state of the sound (playing or not) isn't correctly managed, you could have this problem. This becomes more critical when combining Redux or other state management libraries, and it's essential to track whether a sound is playing or not, and to avoid re-triggering .play() when it is not necessary.
• Concurrency Issues: Concurrency can be tricky. If multiple threads or processes are involved in handling the sound, there might be race conditions that lead to unexpected behavior. For example, if both the sound and the app's state try to access or modify the same resources at the same time, this could cause the sound to restart.

Root Cause Analysis

In the given code, there's no direct handling of the AppState events. This is a potential source of the issue. Without that, there's no mechanism to explicitly stop the sound when the app enters the background or to prevent it from starting again when the app comes back to the foreground. The code triggers the sound using useEffect, which responds to state changes but not necessarily to app focus changes.

The fact that .play() is not called when the sound is replayed indicates that the sound instance may be getting re-initialized or that the app's state is not accurately reflecting the sound's state. It is necessary to correctly handle the application's lifecycle events to prevent the sound from being triggered inadvertently. The main reason for this problem appears to be the lack of correct lifecycle handling.

Solutions and Mitigation Strategies

Let's get into how to solve this React Native sound replay problem and prevent it in iOS. Here are some actionable solutions:

1. Using AppState to Control Sound Playback

The primary solution is to use the AppState API in React Native to manage the sound based on the app's lifecycle events.

• Import AppState: Import the AppState module from 'react-native'.
• Add an AppState Listener: Inside your component, create a useEffect hook to listen for AppState changes. Register an AppState event listener to monitor the app's state (active, inactive, or background). Remove the listener when the component unmounts to prevent memory leaks.
• Handle State Changes: Within the listener, check the current AppState. If the app becomes active (AppState.isActive), and the sound should not be playing, don't play it. If the app goes to the background (AppState.background), stop the sound. Also, make sure that when the app goes from the background to the foreground, you properly check and handle the sound.

Here's an example:

import React, { useEffect, useState } from 'react';
import { AppState } from 'react-native';
import Sound from 'react-native-sound';

// Assuming 'scanSound' is initialized elsewhere

const MySoundComponent = () => {
    const [appState, setAppState] = useState(AppState.currentState);

    useEffect(() => {
        const subscription = AppState.addEventListener('change', nextAppState => {
            setAppState(nextAppState);
        });

        return () => {
            subscription.remove();
        };
    }, []);

    useEffect(() => {
        if (appState === 'background') {
            // Stop the sound when the app goes to the background
            scanSound.stop();
        } else if (appState === 'active') {
            // If the sound was not supposed to play, do nothing
        }
    }, [appState]);

    return null;
};

export default MySoundComponent;

2. Correct Sound Instance Management

• Proper Initialization and Cleanup: Make sure that the sound instance (scanSound in this case) is correctly initialized only once and is disposed of when the component unmounts to prevent memory leaks.
• Sound State: Maintain a state variable to track whether the sound is currently playing or not.
• Stop and Release: When the app enters the background or when the component unmounts, make sure to call scanSound.stop() to stop any current playback. Also, release the sound resource to prevent memory leaks. Use the release() method to free the resources associated with the sound instance. This can be critical to avoid the sound from continuing in the background and for preventing memory issues.

3. Review react-native-sound Library Documentation

Make sure that you're using the right versions of the libraries and follow their recommendations for sound playback in the background or during focus changes. The library's documentation might offer specific instructions or workarounds for focus-related issues.

4. Code Review and Best Practices

• Modular Code: Make your code modular. Put your sound-related logic into separate, reusable components or utility functions. This makes debugging and maintenance much easier.
• Error Handling: Always include proper error handling. Check for errors during sound loading and playback, and handle them gracefully.
• Logging: Use logging statements to track the state of your sound playback and app lifecycle events. This can help you diagnose unexpected behavior.

Conclusion and Best Practices

Fixing the React Native sound replay bug is essential for creating a smooth, user-friendly iOS app. This issue is usually related to how the app handles lifecycle events. The key to fixing this issue is by effectively managing the sound instance state. By using AppState and by managing the sound instance lifecycle correctly, you can prevent unwanted sound replays.

Here's a recap of the best practices:

• Use AppState to monitor the app's state changes.
• Stop the sound when the app enters the background.
• Prevent sound playback when the app is brought to the foreground unless it should play.
• Correctly initialize and release sound instances.
• Always review and adhere to the guidelines of the react-native-sound library.
• Implement thorough error handling and add logging to debug issues.

By following these recommendations, you'll be well on your way to a more stable and user-friendly audio experience in your React Native iOS application. Remember, thorough testing and a good understanding of React Native and iOS lifecycles are crucial for identifying and fixing these types of issues.