Android Fragment结合Navigation Component实现Facebook登录异常排查

问题描述 #

在Activity中实现Facebook登录功能完全正常，但迁移到使用Navigation Component的Fragment后出现异常：点击Facebook登录按钮能弹出授权界面，但点击「继续」后，loginWithFacebook()方法内的Log.i()日志没有触发，回调逻辑未执行。

Fragment代码 #

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    binding = FragmentLoginBinding.inflate(inflater, container, false);
    // facebook callback
    callbackManager = CallbackManager.Factory.create();

    LoginManager.getInstance().registerCallback(callbackManager,
            new FacebookCallback<LoginResult>() {
                @Override
                public void onSuccess(LoginResult loginResult) {
                    // App code
                    loginWithFacebook(loginResult);
                }

                @Override
                public void onCancel() {
                    // App code
                }

                @Override
                public void onError(FacebookException exception) {
                    // App code
                    Log.e("Login With facebook", "onError: ", exception);
                }
            });
    binding.btnRegisterFacebook.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            LoginManager.getInstance().logInWithReadPermissions(requireActivity(), Arrays.asList("public_profile"));
        }
    });
    return binding.getRoot();
}
@Override
public void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
    callbackManager.onActivityResult(requestCode, resultCode, data);
    super.onActivityResult(requestCode, resultCode, data);
}

private void loginWithFacebook(LoginResult loginResult) {
    // here we will get access token and save data to server
    AccessToken accessToken = loginResult.getAccessToken();
    GraphRequest request = GraphRequest.newMeRequest(
            accessToken,
            new GraphRequest.GraphJSONObjectCallback() {
                @Override
                public void onCompleted(
                        JSONObject object,
                        GraphResponse response) {
                    try {
                        String name = object.getString("name");
                        String id = object.getString("id");
                        // save to server
                        Log.i("Facebook auth",id);
                        Log.i("Facebook auth",name);
                    } catch (JSONException e) {
                        Log.e("Login With facebook", "onCompleted: ", e);
                        throw new RuntimeException(e);
                    }
                    // Application code
                }
            });
    Bundle parameters = new Bundle();
    parameters.putString("fields", "id,name,link");
    request.setParameters(parameters);
    request.executeAsync();
}

宿主Activity代码 #

@Override
protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
   Fragment navhost = getSupportFragmentManager().findFragmentById(R.id.nav_host_fragment);
   navhost.onActivityResult(requestCode,resultCode,data);
   super.onActivityResult(requestCode, resultCode, data);
}

排查与解决 #

问题核心是Activity到Fragment的onActivityResult结果分发逻辑错误，以及Fragment回调的生命周期稳定性问题，按以下步骤修复：

• 修正宿主Activity的结果分发逻辑
  直接调用navhost.onActivityResult()无法将结果传递到当前显示的子Fragment，需要通过NavHostFragment的子Fragment管理器分发。同时要先调用super.onActivityResult()：

  @Override
  protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
      super.onActivityResult(requestCode, resultCode, data);
      Fragment navHost = getSupportFragmentManager().findFragmentById(R.id.nav_host_fragment);
      if (navHost != null) {
          // 遍历NavHost下的子Fragment，分发结果
          for (Fragment fragment : navHost.getChildFragmentManager().getFragments()) {
              fragment.onActivityResult(requestCode, resultCode, data);
          }
      }
  }
  

• 确保CallbackManager是Fragment成员变量
  避免在onCreateView中局部声明callbackManager，防止Fragment重建时回调实例丢失，将其声明为Fragment的全局成员：

  public class LoginFragment extends Fragment {
      private FragmentLoginBinding binding;
      // 全局成员变量
      private CallbackManager callbackManager;
  
      @Override
      public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
          binding = FragmentLoginBinding.inflate(inflater, container, false);
          callbackManager = CallbackManager.Factory.create();
          // 后续注册回调逻辑...
          return binding.getRoot();
      }
  }
  

• 改用LoginButton的Fragment绑定方式（推荐）
  对于Fragment场景，Facebook官方推荐直接使用LoginButton并调用setFragment(this)，无需手动处理onActivityResult分发，简化逻辑：

  @Override
  public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
      binding = FragmentLoginBinding.inflate(inflater, container, false);
      callbackManager = CallbackManager.Factory.create();
  
      LoginButton loginButton = binding.btnRegisterFacebook;
      // 将按钮与当前Fragment绑定
      loginButton.setFragment(this);
      loginButton.setReadPermissions(Arrays.asList("public_profile"));
      loginButton.registerCallback(callbackManager, new FacebookCallback<LoginResult>() {
          @Override
          public void onSuccess(LoginResult loginResult) {
              loginWithFacebook(loginResult);
          }
  
          @Override
          public void onCancel() {}
  
          @Override
          public void onError(FacebookException exception) {
              Log.e("Login With facebook", "onError: ", exception);
          }
      });
  
      return binding.getRoot();
  }
  

内容的提问来源于stack exchange，提问作者Mohamed Hossam