React native "Attempt to invoke virtual method 'android.app.Activity.showdShowRequestPermissionRationale' on a null object reference"

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06-10-2024

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React Native: "Attempt to invoke virtual method 'android.app.Activity.showdShowRequestPermissionRationale' on a null object reference" - Solved!

Scenario: You're developing a React Native app that needs user permissions, but you're encountering the frustrating error "Attempt to invoke virtual method 'android.app.Activity.showdShowRequestPermissionRationale' on a null object reference." This cryptic message can leave you scratching your head, wondering what's causing the issue and how to fix it.

Rephrasing: Imagine you're building a camera app, and your code asks for camera access. This error means your app is trying to explain why it needs the permission, but it can't find the relevant Android component (the Activity) needed to do so.

Understanding the Issue

This error occurs when the showRequestPermissionRationale method is called on a null object reference. This usually happens in the following situations:

1. Incorrect PermissionsAndroid.request Usage: The PermissionsAndroid.request method in React Native is used to request permissions. If it is called incorrectly (e.g., before the Activity is ready), it will result in the null reference error.
2. Incorrect Context: The PermissionsAndroid.request method needs to be invoked within a component that has access to the current Activity. If the component is in a different context (e.g., inside a useEffect hook without the correct context), the error can occur.
3. Race Condition: If your code attempts to check for permission before the Activity is fully initialized, it might lead to this issue. This could happen in situations where you have asynchronous code (like fetching data) that runs before the user interface is fully loaded.

Original Code Example

import React, { useState, useEffect } from 'react';
import { PermissionsAndroid } from 'react-native';

const App = () => {
  const [hasPermission, setHasPermission] = useState(false);

  useEffect(() => {
    const requestCameraPermission = async () => {
      try {
        const granted = await PermissionsAndroid.request(
          PermissionsAndroid.PERMISSIONS.CAMERA,
          {
            title: 'Camera Permission',
            message: 'This app needs access to your camera',
          }
        );
        setHasPermission(granted === PermissionsAndroid.RESULTS.GRANTED);
      } catch (err) {
        console.warn(err);
      }
    };
    requestCameraPermission();
  }, []);

  return (
    <View>
      {hasPermission ? (
        <Text>Camera permission granted</Text>
      ) : (
        <Text>Camera permission denied</Text>
      )}
    </View>
  );
};

export default App;

Troubleshooting and Solutions:

1. Context is Key: Make sure you are calling PermissionsAndroid.request within a component that has access to the Activity (usually your main component). This is particularly important for asynchronous operations like useEffect hooks.

2. Delayed Execution: Use a setTimeout or Promise.resolve to delay the permission request until the Activity is ready. This allows for proper initialization and avoids race conditions.

   useEffect(() => {
     // ... other code
     setTimeout(() => {
       requestCameraPermission();
     }, 100); // Delay for 100 milliseconds
   }, []);
   

3. Check Before Requesting: Instead of directly requesting permissions, first use PermissionsAndroid.check to see if the permission is already granted. This can prevent unnecessary attempts to explain rationale:

   useEffect(() => {
     const checkCameraPermission = async () => {
       try {
         const granted = await PermissionsAndroid.check(
           PermissionsAndroid.PERMISSIONS.CAMERA
         );
         setHasPermission(granted);
       } catch (err) {
         console.warn(err);
       }
     };
   
     const requestCameraPermission = async () => {
       // ... (code to request permission)
     };
   
     checkCameraPermission();
     if (!hasPermission) {
       requestCameraPermission();
     }
   }, []);
   

Additional Considerations:

• Use PermissionsAndroid.request sparingly: For a smoother user experience, use PermissionsAndroid.check to verify permissions before requesting them.
• Understand Asynchronous Code: Be mindful of the timing of your permission checks and requests, especially when using asynchronous operations like useEffect.

Remember: By carefully managing context, delaying permission requests, and understanding the asynchronous nature of React Native, you can overcome the "Attempt to invoke virtual method" error and build a seamless permissions flow in your app.