如何检索当前用户 ID 并放入片段

Question

我正在制作一个帐户片段，所以我想检索name和image数据，但它使我的应用程序强制关闭：

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: 尝试在 android.app.ActivityThread.performLaunchActivity 的空对象引用上调用虚拟方法“com.google.firebase.auth.FirebaseUser com.google.firebase.auth.FirebaseAuth.getCurrentUser()” (ActivityThread.java:2744) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2805) at android.app.ActivityThread.-wrap12(ActivityThread.java) at android.app.ActivityThread$H.handleMessage(ActivityThread.java) :1538) 在 android.os.Handler.dispatchMessage(Handler.java:102) 在 android.os.Looper.loop(Looper.java:165) 在 android.app.ActivityThread.main(ActivityThread.java:6354) 在 java .lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:883) a t com.android.internal.os.ZygoteInit.main(ZygoteInit.java:773) 引起：java.lang.NullPointerException：尝试调用虚拟方法'com.google.firebase.auth.FirebaseUser com.google.firebase.auth .FirebaseAuth.getCurrentUser()' 在 com.example.hpprobook.blogapp.AccountFragment.getUser(AccountFragment.java:68) 的空对象引用上，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) at android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:792) at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2596) at android.support。 v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2383) at android.support.v4.app.FragmentManagerImpl.removeRedu ndantOperationsAndExecute(FragmentManager.java:2338) at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2245) at android.support.v4.app.FragmentManagerImpl.dispatchStateChange(FragmentManager.java:3248) at android. .v4.app.FragmentManagerImpl.dispatchActivityCreated(FragmentManager.java:3200) at android.support.v4.app.FragmentController.dispatchActivityCreated(FragmentController.java:195) at 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(Act ivityThread.java) 在 android.app.ActivityThread$H.handleMessage(ActivityThread.java:1538) 在 android.os.Handler.dispatchMessage(Handler.java:102) 在 android.os.Looper.loop(Looper.java:165) ) 在 android.app.ActivityThread.main(ActivityThread.java:6354) 在 java.lang.reflect.Method.invoke(Native Method) 在 com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:883) ) 在 com.android.internal.os.ZygoteInit.main(ZygoteInit.java:773)

这是在这里

getUser();

和这里

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

这是我的主要活动

 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(); } }

它在这里也显示了一些错误

super.onStart();

很抱歉因为我的英语不好，而且我也是这个论坛的新用户，我想我需要被指导。

Answer 1

显然您正在使用未实例化的变量来获取数据。 尝试改变它：

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

tol获取用户的uid，只需使用以下几行代码：

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

检查firebaseUser是否为空也很重要。