Question

我要创建一个帐户片段，所以我想检索name和image数据，但这会使我的应用强制关闭：

这是我的帐户片段：

import android.content.Context;
import android.content.Intent;
import android.net.Uri;
import android.nfc.Tag;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import android.widget.Toast;

import com.bumptech.glide.Glide;
import com.bumptech.glide.request.RequestOptions;
import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
import com.google.firebase.firestore.DocumentSnapshot;
import com.google.firebase.firestore.FirebaseFirestore;
import com.google.firebase.storage.FirebaseStorage;
import com.google.firebase.storage.StorageReference;

import java.util.ArrayList;
import java.util.List;
import java.util.zip.Inflater;

import de.hdodenhof.circleimageview.CircleImageView;

import static android.support.constraint.Constraints.TAG;


/**
 * A simple {@link Fragment} subclass.
 */
public class AccountFragment extends Fragment {

  private StorageReference storageReference;
  private FirebaseAuth firebaseAuth;
  private FirebaseFirestore firebaseFirestore;
  private Uri mainImageURI = null;
  private String user_id;
  private TextView accountName;
  private CircleImageView accountImage;

  public AccountFragment() {
    // Required empty public constructor
  }


  @Override
  public View onCreateView(LayoutInflater inflater, ViewGroup container,
    Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    View view = inflater.inflate(R.layout.fragment_account, container, false);

    getUser();

    return view;
  }

  protected void getUser() {

    FirebaseUser currentUser = FirebaseAuth.getInstance().getCurrentUser();

    user_id = firebaseAuth.getCurrentUser().getUid();
    accountName = getView().findViewById(R.id.account_name);
    accountImage = getView().findViewById(R.id.account_image);

    firebaseFirestore.collection("Users").document(user_id).get().addOnCompleteListener(new OnCompleteListener < DocumentSnapshot > () {
      @Override
      public void onComplete(@NonNull Task < DocumentSnapshot > task) {

        if (task.isSuccessful()) {

          if (task.getResult().exists()) {

            String name = task.getResult().getString("name");
            String image = task.getResult().getString("image");

            mainImageURI = Uri.parse(image);

            accountName.setText(name);

            RequestOptions placeholderRequest = new RequestOptions();
            placeholderRequest.placeholder(R.drawable.person);

            Glide.with(AccountFragment.this).setDefaultRequestOptions(placeholderRequest).load(image).into(accountImage);
          }

        } else {

          String error = task.getException().getMessage();
          Toast.makeText(getContext(), "(FIRESTORE Retrieve Error) : " + error, Toast.LENGTH_LONG).show();

        }


      }
    });

  }
}

这是我的错误日志

11-13 21：35：56.045 15465-15465 /？ E / AndroidRuntime：致命异常：主要进程：com.example.hpprobook.blogapp，PID：15465 java.lang.RuntimeException：无法启动活动ComponentInfo {com.example.hpprobook.blogapp / com.example.hpprobook.blogapp.MainActivity}： java.lang.NullPointerException：尝试调用虚拟方法 'com.google.firebase.auth.FirebaseUser com.google.firebase.auth.FirebaseAuth.getCurrentUser（）”为null 对象参考在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2744）在android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:2805）在android.app.ActivityThread.-wrap12（ActivityThread.java）在android.app.ActivityThread $ H.handleMessage（ActivityThread.java:1538）在android.os.Handler.dispatchMessage（Handler.java:102）在android.os.Looper.loop（Looper.java:165）在android.app.ActivityThread.main（ActivityThread.java:6354）在java.lang.reflect.Method.invoke（本机方法）在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:883）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:773）引起原因：java.lang.NullPointerException：尝试调用虚拟方法'com.google.firebase.auth.FirebaseUser com.google.firebase.auth.FirebaseAuth.getCurrentUser（）”为null 对象参考在com.example.hpprobook.blogapp.AccountFragment.getUser（AccountFragment.java:68）在com.example.hpprobook.blogapp.AccountFragment.onCreateView（AccountFragment.java:62）在android.support.v4.app.Fragment.performCreateView（Fragment.java:2346）在android.support.v4.app.FragmentManagerImpl.moveToState（FragmentManager.java:1428）在android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState（FragmentManager.java:1759）在android.support.v4.app.BackStackRecord.executeOps（BackStackRecord.java:792）在android.support.v4.app.FragmentManagerImpl.executeOps（FragmentManager.java:2596）在android.support.v4.app.FragmentManagerImpl.executeOpsTogether（FragmentManager.java:2383）在android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute（FragmentManager.java:2338）在android.support.v4.app.FragmentManagerImpl.execPendingActions（FragmentManager.java:2245）在android.support.v4.app.FragmentManagerImpl.dispatchStateChange（FragmentManager.java:3248）在android.support.v4.app.FragmentManagerImpl.dispatchActivityCreated（FragmentManager.java:3200）在android.support.v4.app.FragmentController.dispatchActivityCreated（FragmentController.java:195）在android.support.v4.app.FragmentActivity.onStart（FragmentActivity.java:597）在android.support.v7.app.AppCompatActivity.onStart（AppCompatActivity.java:177）在com.example.hpprobook.blogapp.MainActivity.onStart（MainActivity.java:116）在android.app.Instrumentation.callActivityOnStart（Instrumentation.java:1249）在android.app.Activity.performStart（Activity.java:6874）在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2707）在android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:2805）在android.app.ActivityThread.-wrap12（ActivityThread.java）在android.app.ActivityThread $ H.handleMessage（ActivityThread.java:1538）在android.os.Handler.dispatchMessage（Handler.java:102）在android.os.Looper.loop（Looper.java:165）在android.app.ActivityThread.main（ActivityThread.java:6354）在java.lang.reflect.Method.invoke（本机方法）在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:883）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:773）

在这里

getUser();

在这里

user_id = firebaseAuth.getCurrentUser().getUid();

这是我的mainActivity

import android.content.Intent;
import android.nfc.Tag;
import android.support.annotation.NonNull;
import android.support.design.widget.BottomNavigationView;
import android.support.design.widget.FloatingActionButton;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Toast;

import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
import com.google.firebase.firestore.DocumentSnapshot;
import com.google.firebase.firestore.FirebaseFirestore;

public class MainActivity extends AppCompatActivity {

  private Toolbar mainToolbar;
  private FirebaseAuth mAuth;
  private FirebaseFirestore firebaseFirestore;

  private String current_user_id;

  private FloatingActionButton addPostBtn;

  private BottomNavigationView mainbottomNav;

  private HomeFragment homeFragment;
  private NotificationFragment notificationFragment;
  private AccountFragment accountFragment;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    mAuth = FirebaseAuth.getInstance();
    firebaseFirestore = FirebaseFirestore.getInstance();

    mainToolbar = (Toolbar) findViewById(R.id.main_toolbar);
    setSupportActionBar(mainToolbar);

    getSupportActionBar().setTitle("PhotoGram");

    if (mAuth.getCurrentUser() != null) {

      mainbottomNav = findViewById(R.id.mainbottom_nav);

      // FRAGMENTS
      homeFragment = new HomeFragment();
      notificationFragment = new NotificationFragment();
      accountFragment = new AccountFragment();

      initializeFragment();

      mainbottomNav.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
        @Override
        public boolean onNavigationItemSelected(@NonNull MenuItem item) {

          Fragment currentFragment = getSupportFragmentManager().findFragmentById(R.id.main_container);

          switch (item.getItemId()) {

            case R.id.bottom_home_btn:

              replaceFragment(homeFragment, currentFragment);
              return true;

            case R.id.bottom_account_btn:

              replaceFragment(accountFragment, currentFragment);
              return true;

            case R.id.bottom_notification_btn:

              replaceFragment(notificationFragment, currentFragment);
              return true;

            default:
              return false;


          }

        }
      });


      addPostBtn = findViewById(R.id.add_post_btn);
      addPostBtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

          Intent newPostIntent = new Intent(MainActivity.this, NewPostActivity.class);
          startActivity(newPostIntent);

        }
      });
    }
  }

  @Override
  protected void onStart() {
    super.onStart();

    FirebaseUser currentUser = FirebaseAuth.getInstance().getCurrentUser();
    if (currentUser == null) {

      sendToLogin();

    } else {

      current_user_id = mAuth.getCurrentUser().getUid();

      firebaseFirestore.collection("Users").document(current_user_id).get().addOnCompleteListener(new OnCompleteListener < DocumentSnapshot > () {
        @Override
        public void onComplete(@NonNull Task < DocumentSnapshot > task) {

          if (task.isSuccessful()) {

            if (!task.getResult().exists()) {

              Intent setupIntent = new Intent(MainActivity.this, SetupActivity.class);
              startActivity(setupIntent);
              finish();

            }

          } else {

            String errorMessage = task.getException().getMessage();
            Toast.makeText(MainActivity.this, "Error : " + errorMessage, Toast.LENGTH_LONG).show();
          }
        }
      });
    }
  }


  @Override
  public boolean onCreateOptionsMenu(Menu menu) {

    getMenuInflater().inflate(R.menu.main_menu, menu);
    return true;

  }

  @Override
  public boolean onOptionsItemSelected(MenuItem item) {

    switch (item.getItemId()) {

      case R.id.action_logout_btn:
        logOut();
        return true;

      case R.id.action_setting_btn:

        Intent settingsIntent = new Intent(MainActivity.this, SetupActivity.class);
        startActivity(settingsIntent);

        return true;


      default:
        return false;


    }

  }

  private void logOut() {


    mAuth.signOut();
    sendToLogin();
  }

  private void sendToLogin() {

    Intent loginIntent = new Intent(MainActivity.this, LoginActivity.class);
    startActivity(loginIntent);
    finish();

  }

  private void initializeFragment() {

    FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();

    fragmentTransaction.add(R.id.main_container, homeFragment);
    fragmentTransaction.add(R.id.main_container, notificationFragment);
    fragmentTransaction.add(R.id.main_container, accountFragment);

    fragmentTransaction.hide(notificationFragment);
    fragmentTransaction.hide(accountFragment);

    fragmentTransaction.commit();

  }

  private void replaceFragment(Fragment fragment, Fragment currentFragment) {

    FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
    if (fragment == homeFragment) {

      fragmentTransaction.hide(accountFragment);
      fragmentTransaction.hide(notificationFragment);

    }

    if (fragment == accountFragment) {

      fragmentTransaction.hide(homeFragment);
      fragmentTransaction.hide(notificationFragment);

    }

    if (fragment == notificationFragment) {

      fragmentTransaction.hide(homeFragment);
      fragmentTransaction.hide(accountFragment);

    }
    fragmentTransaction.show(fragment);

    //fragmentTransaction.replace(R.id.main_container, fragment);
    fragmentTransaction.commit();

  }

}

这里也显示了一些错误

super.onStart();

很抱歉，因为我的英语不好，而且我也是该论坛的新用户，我认为我需要得到指导。

Answer 1

显然，您使用的是非即时变量来获取数据。尝试将其更改为：

protected void getUser() {

FirebaseUser currentUser = FirebaseAuth.getInstance().getCurrentUser();

user_id = currentUser.getUid();
....
}

Answer 2

这对我有用：

//in Class definition.
private FirebaseFirestore firebaseFirestore;
private FirebaseAuth firebaseAuth;
private FirebaseUser currentUser;

//Declareation in Oncreate()
currentUser = firebaseAuth.getCurrentUser();
userId = currentUser.getUid();
private void setUserName() {
    /*
        Assign the value of profile_name_of field in the document of the current user
        under Users collection.
        pre:---.
        post: changes the value of the instance variable of username.
     */

    firebaseFirestore.collection("Users").document(userId)
            .get().addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() {

        @Override
        public void onComplete(@NonNull Task<DocumentSnapshot> task) {
            DocumentSnapshot documentSnapshot = task.getResult();

            if(documentSnapshot.exists()){

                List<String> list = new ArrayList<>();
                Map<String, Object> map = documentSnapshot.getData();

                if(map != null){

                    for(Map.Entry<String, Object> entry : map.entrySet()){
                        list.add(entry.getValue().toString());
                    }

                    username = list.get(0);
                    Toast.makeText(context,
                          "username"+username,
                          Toast.LENGTH_LONG).show();
                }
            }
        }
    });
}

Answer 3

要获取用户的uid，只需使用以下代码行：

FirebaseUser firebaseUser = FirebaseAuth.getInstance().getCurrentUser();
if (firebaseUser != null) {
    String uid = firebaseUser.getUid(); //Do what you need to do with your uid
}

检查firebaseUser是否无效也很重要。

如何获取当前用户ID并将其放入片段

3 个答案: