Hey there, let's walk through why your Facebook login stopped working (even though it was fine before) and how to fix it. Let's start with the most likely culprits first:

1. Outdated Facebook SDK Version (Big Red Flag!) #

You're using version 5.0.0 of the Facebook Login SDK, which is extremely outdated (released back in 2019). Facebook regularly deprecates old SDK versions due to security updates, API endpoint changes, and policy shifts. Old SDKs often stop working entirely when Facebook sunsets the corresponding Graph API versions.

Fix: Upgrade to the Latest Stable SDK #

Update your dependency in build.gradle (Module level) to the latest stable version (as of now, v17.0.0 is current):

implementation 'com.facebook.android:facebook-login:17.0.0'

After updating, sync your Gradle project. Note: Make sure other Facebook-related dependencies (like facebook-core if you use them) are also on matching versions to avoid conflicts.

2. Check Facebook Developer Dashboard Configurations #

Even if nothing changed in your code, settings in the Facebook Developer Dashboard might have been altered (or Facebook updated their requirements):

• App Status: Ensure your app is set to Live (not "In Development"). Apps in Development mode only allow logins from registered test users, which won't work for your production app on Google Play.
• Android Platform Settings:
  • Double-check your Package Name matches exactly what's in your app's AndroidManifest.xml.
  • Signing Hashes: If you use Google Play App Signing (which is mandatory for most apps), you need to add the SHA-1 hash from Google Play's App Signing Certificate (not your local debug/release keystore hash) to the Facebook Dashboard. You can find this in your Google Play Console under Release > Setup > App signing.
• Login Permissions: Confirm that email and public_profile are still listed as approved permissions for your app. While these are basic permissions, sometimes Facebook can revoke access if there's a policy violation (though this is less likely if your app was already live).
• OAuth Redirect URIs: In the Facebook Dashboard under Products > Login > Settings, ensure the Android redirect URI is fb{YOUR_APP_ID}://authorize (replace {YOUR_APP_ID} with your actual Facebook App ID).

3. Add Error Logging to Diagnose Exact Issues #

Your current code has an empty onError method, which means you're missing critical error information that could tell you exactly what's wrong. Let's fix that:

@Override
public void onError(FacebookException exception) {
    Log.e("FacebookLogin", "Login failed: " + exception.getMessage(), exception);
    // Optional: Show a user-friendly error message here
}

Run your app and check Logcat for errors. Common issues you might see:

• Invalid key hash: Means your signing hash in Facebook Dashboard doesn't match the app's actual signing hash.
• App not live: Your app is still in Development mode.
• Permission denied: The user didn't grant the required permissions, or Facebook blocked them.
• Graph API error: The Graph Request is failing (often due to outdated API versions).

4. Review Graph API Usage #

When you upgrade the SDK, it will automatically use a newer Graph API version (which is required, since old versions are deprecated). Double-check your Graph Request fields:

• Ensure the fields you're requesting (first_name, last_name, email, id) are still valid in the latest Graph API. As of now, these fields are still supported, but Facebook sometimes renames or removes fields.
• Verify your parameters.putString call is using the correct field names. If your R.string.fbrequiedfields is something like "first_name,last_name,email,id", that's still valid, but confirm it's not using deprecated fields.

5. Test with a Release Build #

Sometimes debug builds work fine, but release builds fail because of signing hash mismatches. Make sure you test the exact same build variant that you uploaded to Google Play. If you use app bundles (.aab), generate a signed APK from the bundle to test locally.

内容的提问来源于stack exchange，提问作者mahesh kumar