Facebook login issues in WebView can occur for a variety of reasons. Here are some potential causes and solutions for debugging Facebook login in your WebView implementation.
Possible Causes
There are a few common reasons why Facebook login may not be working properly in a WebView:
- Incorrect Facebook App ID – Make sure you are using the correct Facebook App ID for your app in the WebView initialization.
- API version mismatch – Ensure the Facebook SDK version in your native app matches the version used by the WebView Facebook JS SDK.
- Facebook domain whitelist issue – The Facebook domains need to be whitelisted in the WebView config to allow proper API access.
- Cert pinning conflict – If certificate pinning is implemented, it needs to allow Facebook domains.
- URL scheme mismatch – The URL scheme registered for the app should match what’s configured in the Facebook app settings.
- Token storage conflict – The Facebook token may not be properly stored/retrieved between the WebView and native context.
- JavaScript enabled – JavaScript needs to be enabled in the WebSettings for the WebView.
- Customtabs conflict – Other Facebook login implementations using Customtabs can conflict with WebView.
- CORS origin header missing – The CORS allowed origins may need to be updated on the server if necessary.
Step-by-Step Debugging
Here are some steps to help debug Facebook login issues in your WebView app:
- Verify you are using the current Facebook login SDK in the WebView code.
- Make sure the Facebook App ID matches your app ID in the Facebook developer portal.
- Try logging in on https://developers.facebook.com/apps/YOUR_APP_ID/fb-login/ to validate credentials.
- Enable WebView debugging to inspect for JavaScript errors.
- Check that Facebook domains are whitelisted in your WebView configuration.
- Test that the registered URL scheme matches your Facebook app settings.
- Validate there are no certificate pinning conflicts.
- Ensure the Facebook SDK JavaScript is loaded before calling FB.login().
- Check that the access token is persisted properly between WebView and native context.
- Make sure JavaScript is enabled in the WebView settings.
- Try disabling other Facebook SDK login implementations to isolate issue.
- Verify CORS allowed origins on server include Facebook domains.
Common WebView Configuration
Here is sample code for a basic WebView configuration that supports Facebook login:
“`java
WebView webView = new WebView(this);
WebSettings webSettings = webView.getSettings();
webSettings.setJavaScriptEnabled(true);
webView.setWebViewClient(new WebViewClient());
webSettings.setUserAgentString(“MyAppName/1.0”);
webSettings.setDomStorageEnabled(true);
webSettings.setAppCacheEnabled(true);
webSettings.setAppCachePath(getApplicationContext().getCacheDir().getAbsolutePath());
webSettings.setAllowFileAccess(true);
webView.loadUrl(“http://mydomain.com”);
“`
Key points:
- JavaScript must be enabled
- DOM storage enabled to allow token persistence
- Set user agent string
- Allow file access
Whitelisting Facebook Domains
To allow proper API access, Facebook requires whitelisting their domains in WebView:
“`java
webView.setWebViewClient(new WebViewClient() {
@Override
public WebResourceResponse shouldInterceptRequest(WebView view, String url) {
if (url.contains(“facebook.com”) || url.contains(“fbcdn.net”)) {
return null;
}
// Default behavior for other domains
}
}
});
“`
This allows requests to Facebook while intercepting other domains. The Facebook docs provide the full up-to-date list of required domains to whitelist.
Troubleshooting Token Handling
One common issue is managing the access token properly between the WebView context and native app. The Facebook docs provide guidance on securely handling the token flow:
- Generate token in WebView using FB SDK
- Return token back to native app via JavaScript bridge
- Store token securely in native storage like Keychain
- Pass token back to WebView when needed
This ensures the token is persisted securely in the native layer vs. within WebView storage.
Conflicts with Other Facebook SDKs
If you have other Facebook SDK login implementations in your native app like Customtabs, make sure to disable them when testing WebView login. Having multiple active can result in conflicts.
Try fully removing any other Facebook SDK login integrations and test just the WebView implementation in isolation.
Enabling CORS on Server
For apps calling an external API server from the WebView, make sure CORS allows the Facebook domains:
“`
header(‘Access-Control-Allow-Origin: https://www.facebook.com’);
header(‘Access-Control-Allow-Origin: https://facebook.com’);
“`
The server needs to enable the Facebook domains in the CORS allowed origins to allow API requests.
Conclusion
Debugging Facebook login in WebView can take some trial and error, but is commonly caused by issues like incorrect configuration, whitelisting needs, token handling, or conflicts with other SDKs. Following Facebook’s troubleshooting tips and validating the required settings are enabled can help isolate the problem. Tracing through the full login flow and API calls can shed light on where things may be breaking down.
Some key areas to focus on include:
- Ensuring JavaScript is enabled
- Whitelisting Facebook domains
- Handling tokens securely between WebView and native context
- Disabling other Facebook SDK implementations
- Enabling CORS allowed origins on API server if necessary
With proper configuration and validation of the various requirements, Facebook login can be integrated successfully into WebView applications.