我试图让用户登录，如果他在我不能登录之前登录，但是使用片段时却无法工作，它给了我空指针异常
MainActivity
public class MainActivity extends AppCompatActivity {
private static final String TAG = "MainActivity";
private FirebaseAuth auth;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
auth = FirebaseAuth.getInstance();
if(auth != null) {
BottomNavigationView bottomNavigationView = findViewById(R.id.bottom_navigation);
bottomNavigationView.setOnNavigationItemSelectedListener(navListener);
getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container, new LeadsFragment()).commit();
}
}
private BottomNavigationView.OnNavigationItemSelectedListener navListener = new BottomNavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem menuItem) {
Fragment selectedFragment = null;
switch (menuItem.getItemId()) {
case R.id.main_leads:
selectedFragment = new LeadsFragment();
break;
case R.id.main_bank_details:
selectedFragment = new BankDetailsFragment();
break;
case R.id.main_payment:
selectedFragment = new PaymentFragment();
break;
}
// Update Ui
getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container, selectedFragment).commit();
return true;
}
};
@Override
public boolean onCreateOptionsMenu(Menu menu) {
return super.onCreateOptionsMenu(menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.lead_logout:
logOut();
case R.id.lead_add_lead:
Intent addNewLeadIntent = new Intent(this, AddLeadActivity.class);
startActivity(addNewLeadIntent);
default:
return super.onOptionsItemSelected(item);
}
}
private void logOut() {
auth.signOut();
// Update UI
Intent loginIntent = new Intent(this, LoginActivity.class);
loginIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK | Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(loginIntent);
}
@Override
public void onStart() {
super.onStart();
FirebaseUser currentUser = FirebaseAuth.getInstance().getCurrentUser();
if (currentUser == null) {
sendToLogin();
} else {
Log.d(TAG, "onStart: signed in");
}
}
private void sendToLogin(){
Intent loginIntent = new Intent(MainActivity.this, LoginActivity.class);
loginIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK | Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(loginIntent);
finish();
}
LoginActivity
public class LoginActivity extends AppCompatActivity {
private FirebaseAuth auth;
private EditText emailPhoneEd, passwordEd;
private Button loginBtn;
private TextView goToRegister;
private ProgressBar progressBar;
private Toolbar toolbar;
private TextView forgotPassword;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);
auth = FirebaseAuth.getInstance();
toolbar = findViewById(R.id.login_toolbar);
setSupportActionBar(toolbar);
getSupportActionBar().setTitle("Login");
emailPhoneEd = findViewById(R.id.login_email_phone_ed);
passwordEd = findViewById(R.id.login_password);
progressBar = findViewById(R.id.login_progress);
loginBtn = findViewById(R.id.login_btn);
forgotPassword = findViewById(R.id.login_forgot_password);
forgotPassword.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
showRecoverPasswordDialoge();
}
});
loginBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
String email = emailPhoneEd.getText().toString();
String password = passwordEd.getText().toString();
signInUser(email, password);
}
});
goToRegister = findViewById(R.id.login_go_to_register);
goToRegister.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
sendToRegister();
}
});
}
@Override
protected void onStart() {
super.onStart();
FirebaseUser currentUser = FirebaseAuth.getInstance().getCurrentUser();
if(currentUser != null){
Intent mainIntent = new Intent(LoginActivity.this , MainActivity.class);
mainIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK | Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(mainIntent);
finish();
}
}
private void beginRecovery(String email) {
auth.sendPasswordResetEmail(email).addOnCompleteListener(new OnCompleteListener<Void>() {
@Override
public void onComplete(@NonNull Task<Void> task) {
if (task.isSuccessful()) {
Toast.makeText(LoginActivity.this, "Email Sent", Toast.LENGTH_SHORT).show();
} else {
Toast.makeText(LoginActivity.this, task.getException().getMessage(), Toast.LENGTH_SHORT).show();
}
}
});
}
private void signInUser(String email, String passwrod) {
enableProgressBar();
if (TextUtils.isEmpty(email) || TextUtils.isEmpty(passwrod)) {
Toast.makeText(this, "Please fill all the fileds", Toast.LENGTH_SHORT).show();
disableProgressBar();
} else {
auth.signInWithEmailAndPassword(email, passwrod).addOnCompleteListener(new OnCompleteListener<AuthResult>() {
@Override
public void onComplete(@NonNull Task<AuthResult> task) {
if (task.isSuccessful()) {
Toast.makeText(LoginActivity.this, "Sign in complete", Toast.LENGTH_SHORT).show();
Intent mainIntent = new Intent(LoginActivity.this, MainActivity.class);
mainIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK | Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(mainIntent);
finish();
} else {
Toast.makeText(LoginActivity.this, task.getException().getMessage(), Toast.LENGTH_SHORT).show();
}
disableProgressBar();
}
});
}
}
private void sendToRegister() {
Intent registerIntent = new Intent(LoginActivity.this, RegisterActivity.class);
startActivity(registerIntent);
finish();
}
private void enableProgressBar() {
progressBar.setVisibility(View.VISIBLE);
loginBtn.setVisibility(View.INVISIBLE);
}
private void disableProgressBar() {
progressBar.setVisibility(View.INVISIBLE);
loginBtn.setVisibility(View.VISIBLE);
}
}
Logcat注释（LeadFragment是片段中的第一个活动或主要活动）
07-10 14:03:16.885 7243-7243/com.best.karem.mycareassociates E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.best.karem.mycareassociates, PID: 7243
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.best.karem.mycareassociates/com.best.karem.mycareassociates.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.google.firebase.auth.FirebaseUser.getUid()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.google.firebase.auth.FirebaseUser.getUid()' on a null object reference
at com.best.karem.mycareassociates.Fragments.LeadsFragment.onCreateView(LeadsFragment.java:103)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:2439)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1460)
at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1784)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1852)
at android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:802)
at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2625)
at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2411)
at android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2366)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2273)
at android.support.v4.app.FragmentManagerImpl.dispatchStateChange(FragmentManager.java:3273)
at android.support.v4.app.FragmentManagerImpl.dispatchActivityCreated(FragmentManager.java:3229)
at android.support.v4.app.FragmentController.dispatchActivityCreated(FragmentController.java:201)
at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:620)
at android.support.v7.app.AppCompatActivity.onStart(AppCompatActivity.java:178)
at com.best.karem.mycareassociates.MainActivity.onStart(MainActivity.java:123)
at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1237)
at android.app.Activity.performStart(Activity.java:6253)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2379)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
我尝试将这段代码放在LeadFragment中，但是它不起作用，并试图使主活动成为登录活动，并且它也行不通。我需要帮助，因为这是我第一次将其作为片段
铅碎片
public class LeadsFragment extends Fragment {
private RecyclerView recyclerView;
private Toolbar toolbar;
private FirebaseAuth auth;
private Context context;
private DatabaseReference leadRef;
private FirebaseRecyclerAdapter<Lead, LeadViewHolder> adapter;
private ProgressBar progressBar;
private Lead currentLead;
private String name;
private String contactPhone;
private String amount;
private String info;
private String purpose;
private String status;
private long actionDate;
private String paymentSanctioned;
private String current_user;
private String payoutAmount;
// @RequiresApi(api = Build.VERSION_CODES.N)
@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.leads_activity, container, false);
toolbar = view.findViewById(R.id.leads_toolbar);
((AppCompatActivity) getActivity()).setSupportActionBar(toolbar);
((AppCompatActivity) getActivity()).getSupportActionBar().setTitle("Leads");
toolbar.getOverflowIcon().setColorFilter(Color.WHITE, PorterDuff.Mode.SRC_ATOP);
setHasOptionsMenu(true);
auth = FirebaseAuth.getInstance();
current_user = auth.getCurrentUser().getUid();
// current_user = auth.getCurrentUser().getUid();
recyclerView = view.findViewById(R.id.leads_recyclerview);
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
recyclerView.addItemDecoration(new DividerItemDecoration(getContext(), DividerItemDecoration.VERTICAL));
progressBar = view.findViewById(R.id.leads_progress);
leadRef = FirebaseDatabase.getInstance().getReference().child("Leads");
Handler handler = new Handler();
handler.postDelayed(new Runnable() {
@Override
public void run() {
progressBar.setVisibility(View.GONE);
recyclerView.setVisibility(View.VISIBLE);
}
}, 1000);
adapter = new FirebaseRecyclerAdapter<Lead, LeadViewHolder>(
Lead.class,
R.layout.lead_item,
LeadViewHolder.class,
leadRef.orderByChild("userId").equalTo(current_user)
) {
@Override
protected void populateViewHolder(LeadViewHolder viewHolder, Lead model, final int position) {
viewHolder.leadName.setText(model.getName());
final String key = adapter.getRef(position).getKey();
leadRef.child(key).addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
currentLead = dataSnapshot.getValue(Lead.class);
name = currentLead.getName();
contactPhone = currentLead.getContactPhone();
amount = currentLead.getAmount();
info = currentLead.getInfo();
purpose = currentLead.getPurpose();
status = currentLead.getStatus();
actionDate = currentLead.getActionDate();
paymentSanctioned = currentLead.getSanctionedPayment();
payoutAmount = currentLead.getPayoutAmount();
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
viewHolder.leadCardView.setOnClickListener(new View.OnClickListener() {
@RequiresApi(api = Build.VERSION_CODES.N)
@Override
public void onClick(View view) {
Toast.makeText(getContext(), key, Toast.LENGTH_SHORT).show();
AlertDialog.Builder builder = new AlertDialog.Builder(getContext());
builder.setTitle("Lead Information");
builder.setMessage(
"Name: " + name + "\n\n" +
"Contact Phone: " + contactPhone + "\n\n" +
"Amount: " + amount + "\n\n" +
"Info: " + info + "\n\n" +
"Purpose: " + purpose + "\n\n" +
"Status: " + status + "\n\n" +
"Action Date: " + getDate(actionDate) + "\n\n" +
"Payment Sanctioned: " + paymentSanctioned + "\n\n" +
"PayOut Amount: " + payoutAmount + "\n\n"
);
builder.setCancelable(true);
builder.setPositiveButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialogInterface, int i) {
dialogInterface.cancel();
}
});
AlertDialog alertDialog = builder.create();
alertDialog.show();
}
});
}
};
recyclerView.setAdapter(adapter);
adapter.notifyDataSetChanged();
return view;
}
@Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
super.onCreateOptionsMenu(menu, inflater);
inflater.inflate(R.menu.leads_menu, menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.lead_logout:
logOut();
case R.id.lead_add_lead:
Intent addNewLeadIntent = new Intent(getContext(), AddLeadActivity.class);
startActivity(addNewLeadIntent);
default:
return super.onOptionsItemSelected(item);
}
}
private String getDate(long actionDate) {
SimpleDateFormat sfd = new SimpleDateFormat("dd-MM-yyyy HH:mm:ss");
return sfd.format(new Date(actionDate));
}
private void logOut() {
auth.signOut();
// Update UI
Intent loginIntent = new Intent(getContext(), LoginActivity.class);
loginIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK | Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(loginIntent);
}