I have my MainActivity in which I handle the logout. Problem is after I log out, the app crashes in verifyUserExistance() at line:
String userID = Objects.requireNonNull(mAuth.getCurrentUser()).getUid();
Which gives :
E/AndroidRuntime: FATAL EXCEPTION: main Process: com.google.firebase.quickstart.auth, PID: 8459 java.lang.NullPointerException at java.util.Objects.requireNonNull(Objects.java:203) at com.google.firebase.quickstart.auth.social.Main_Chat_Activity$3.lambda$null$1$Main_Chat_Activity$3(Main_Chat_Activity.java:372) at com.google.firebase.quickstart.auth.social.-$$Lambda$Main_Chat_Activity$3$87CwjFnoJAhucBGNsLP_MxK833o.onComplete(Unknown Source:2) at com.google.android.gms.tasks.zzj.run(com.google.android.gms:play-services-tasks@@17.2.0:4) at android.os.Handler.handleCallback(Handler.java:873) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:214) at android.app.ActivityThread.main(ActivityThread.java:7050) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:494) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:965)
Below is the code I use:
@Override
protected void onStart() {
super.onStart();
usersRef.child(mAuth.getCurrentUser().getUid()).addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot snapshot) {
if (!snapshot.hasChild("name"))
{
sendUserToLoginActivity();
}
}
@Override
public void onCancelled(@NonNull DatabaseError error) {
}
});
if (mAuth == null || currentUser == null || mAuth.getCurrentUser().getUid() == null ){
finish();
sendUserToLoginActivity();
}
else {
if(mAuth.getCurrentUser().getProviderId() == "google.com"){
user.setmGoogleSignInClient(mGoogleSignInClient);
}
user.setMauth(mAuth);
if (loginOutFlag>-1)
verifyUserExistence();
}
checkLocation();
if (isNew!=null)
{
if (isNew.equals("true")){
sendUserToSettingsActivity();
}
}
}
The method verifyUserExistance is;
private void verifyUserExistence() {
if (!verified && loginOutFlag > -1) {
String currentUserID = mAuth.getCurrentUser().getUid();
try {
rootRef.child("Users").child(currentUserID).addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
if (dataSnapshot.child("name").exists()) {
loginOutFlag = 1;
Toast.makeText(Main_Chat_Activity.this, "Welcome" + dataSnapshot.child("name").getValue().toString(), Toast.LENGTH_SHORT).show();
Log.w("Reportname:", dataSnapshot.child("name").getValue().toString());
Calendar cal = Calendar.getInstance();
final String timeNDate = cal.getTime().toString();
HashMap<String, Object> profileMap = new HashMap<>();
profileMap.put("connection", timeNDate);
rootRef.child("Users").child(currentUserID).updateChildren(profileMap)
.addOnCompleteListener(task ->
{
if (task.isSuccessful()) {
Toast.makeText(Main_Chat_Activity.this, "Success ", Toast.LENGTH_SHORT).show();
verified = true;
FirebaseMessaging.getInstance().getToken()
.addOnCompleteListener(task13 -> {
String userID = Objects.requireNonNull(mAuth.getCurrentUser()).getUid();
if (!task13.isSuccessful()) {
Log.w("FCM", "Fetching FCM registration token failed", task13.getException());
return;
}
// Get new FCM registration token
String deviceToken = task13.getResult();
// Log and toast
Log.d("FCM", deviceToken);
Toast.makeText(Main_Chat_Activity.this, deviceToken, Toast.LENGTH_SHORT).show();
final int[] no = {0};
DatabaseReference tokens = usersRef.child(userID).child("device_tokens");
ValueEventListener valueEventListener = new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot snapshot) {
no[0] = (int) snapshot.getChildrenCount();
}
@Override
public void onCancelled(@NonNull DatabaseError error) {
}
};
tokens.addListenerForSingleValueEvent(valueEventListener);
String devName = "device" + no[0];
String token = deviceToken.split(":")[1];
usersRef.child(userID).child("device_tokens").child(devName)
.setValue(token)
.addOnCompleteListener(task12 -> {
if (task12.isSuccessful()) {
Toast.makeText(Main_Chat_Activity.this, "Token updated succesfully.", Toast.LENGTH_LONG).show();
}
});
});
} else {
String errorMSG = Objects.requireNonNull(task.getException()).toString();
//user.setMauth(null);
Toast.makeText(Main_Chat_Activity.this, "Error : " + errorMSG, Toast.LENGTH_SHORT).show();
}
});
}
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});
}
catch (Exception e)
{
Log.d("EXCEPTION", e.toString());
}
}
}
and this is how I handle the logout;
@Override
public boolean onOptionsItemSelected(MenuItem item) {
super.onOptionsItemSelected(item);
if (item.getItemId() == R.id.main_logout_option) {
updateUserStatus("offline");
String currentUserID = mAuth.getCurrentUser().getUid();
rootRef.child("Users").child(currentUserID).addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
if (dataSnapshot.child("name").exists()) {
Calendar cal = Calendar.getInstance();
final String timeNDate = cal.getTime().toString();
HashMap<String, Object> profileMap = new HashMap<>();
profileMap.put("connection", timeNDate);
rootRef.child("Users").child(currentUserID).updateChildren(profileMap)
.addOnCompleteListener(task ->
{
if (task.isSuccessful()) {
loginOutFlag = -1;
} else {
String errorMSG = Objects.requireNonNull(task.getException()).toString();
Toast.makeText(Main_Chat_Activity.this, "This error : " + errorMSG, Toast.LENGTH_SHORT).show();
}
mGoogleSignInClient.signOut().addOnCompleteListener(task1 -> {
if (task1.isSuccessful()){
mAuth.signOut(); // very important if you are using firebase.
LoginManager.getInstance().logOut();
sendUserToLoginActivity();
finish();
}
});
});
}
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});
sendUserToLoginActivity();
}
if (item.getItemId() == R.id.main_settings_option) {
sendUserToSettingsActivity();
}
if (item.getItemId() == R.id.main_find_friends_option) {
sendUserToFindFriendsActivity();
}
return true;
}
