Android应用Google+登录仅二次生效问题技术求助

Hey there, let's dig into this Google Sign-In issue where the user object comes up null on first login but works perfectly on the second attempt. Here are some targeted troubleshooting directions based on common pitfalls with this integration:

• Validate the timing of user info fetch
  The most common culprit here is trying to access the user object before the Google Sign-In callback has fully completed. For example, if you're fetching user data right in onActivityResult without waiting for the GoogleSignInAccount to be fully resolved, you'll hit a null on first login.
  Make sure you extract user details only after the sign-in task confirms success. Use the completion listener for the sign-in task to handle this safely:

  Task<GoogleSignInAccount> task = GoogleSignIn.getSignedInAccountFromIntent(data);
  task.addOnCompleteListener(this, new OnCompleteListener<GoogleSignInAccount>() {
      @Override
      public void onComplete(@NonNull Task<GoogleSignInAccount> task) {
          if (task.isSuccessful()) {
              GoogleSignInAccount account = task.getResult();
              if (account != null) {
                  // This is the safe spot to pull user info like display name or email
                  String userDisplayName = account.getDisplayName();
                  // Proceed with your remaining field collection flow here
              }
          }
      }
  });
  

• Double-check your Sign-In Options configuration
  If your GoogleSignInOptions isn't configured to request the necessary user data, you'll get an empty object on first authorization. Ensure you're requesting profile and email data explicitly:

  GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
          .requestProfile() // Required to get display name, profile pic, etc.
          .requestEmail()
          .build();
  

  Without these flags, even after successful login, the user account object won't carry the data you need on first attempt.

• Inspect local cache reliance
  The fact that it works on the second login suggests you might be pulling user data from local cache (like GoogleSignIn.getLastSignedInAccount(this)) on app start. On first login, this cache is empty, hence the null. On the second run, the cache is populated from the first successful login.
  Separate your logic: use the sign-in callback to fetch fresh data on first login, and fall back to cache only for subsequent sessions.

• Check Activity lifecycle misalignment
  If you're trying to load user data in onCreate or onStart of your SignInOptionsActivity before the login flow has finished, you'll hit a null. Ensure your user data processing logic is triggered only after the user completes the sign-in flow via the callback, not during Activity initialization.

• Debug with targeted logging
  Add logs at key points to pinpoint exactly where the null is coming from. For example:

  Log.d("SignInDebug", "GoogleSignInAccount status: " + (account == null ? "NULL" : "NOT NULL"));
  if (account != null) {
      Log.d("SignInDebug", "Display Name: " + account.getDisplayName());
      Log.d("SignInDebug", "Email: " + account.getEmail());
  }
  

  This will tell you if the entire GoogleSignInAccount is null, or just specific fields you're trying to access.

内容的提问来源于stack exchange，提问作者Naman Jain