登录成功后如何 go 回到 MainActivity？

Question

After login successful this returns to Main2Activity and I can log in again and again.but start app again after closing and removing from recent list it start in MainActivity. how to directly navigate Main2Activity to MainActivity after if condition is true.

Main2Activity code

public class Main2Activity extends AppCompatActivity {

    private static final String TAG = "Main2Activity";
    int AUTHUI_REQUEST_CODE = 1001;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);

        if (FirebaseAuth.getInstance().getCurrentUser() != null) {
            startActivity(new Intent(this, MainActivity.class));
            this.finish();
        }
    }

    public void loginRegister(View view) {

        List<AuthUI.IdpConfig> providers = Arrays.asList(
                new AuthUI.IdpConfig.EmailBuilder().build(),
                new AuthUI.IdpConfig.GoogleBuilder().build(),
                new AuthUI.IdpConfig.PhoneBuilder().build()
        );

        Intent intent = AuthUI.getInstance()
                .createSignInIntentBuilder()
                .setAvailableProviders(providers)
                .setTosAndPrivacyPolicyUrls("https://example.com","https://example.com")
                .setLogo(R.drawable.i789)
                .build();

        startActivityForResult(intent, AUTHUI_REQUEST_CODE);
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == AUTHUI_REQUEST_CODE){
            if (requestCode == RESULT_OK){
                FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
                Log.d(TAG, "onActivityResult: "+ user.getEmail());
                if (user.getMetadata().getCreationTimestamp() == user.getMetadata().getLastSignInTimestamp()){
                    Toast.makeText(this, "Welcome", Toast.LENGTH_SHORT).show();
                }else{
                    Toast.makeText(this, "Welcome back again", Toast.LENGTH_SHORT).show();
                }
            Intent t = new Intent(this,MainActivity.class);
             startActivity(t);
             this.finish();

        }else{
                IdpResponse response =IdpResponse.fromResultIntent(data);
                if (response == null){
                    Log.d(TAG, "onActivityResult: the user has cancelled the sign in request");
                }else {
                    Log.e(TAG, "onActivityResult: ",response.getError() );
                }

            }
        }
    }
}

code- Main Activity

public class MainActivity extends AppCompatActivity implements FirebaseAuth.AuthStateListener {
    private static final String TAG = "MainActivity";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

        private void startLogin(){
                Intent intent = new Intent(this,Main2Activity.class);
                startActivity(intent);
                finish();
        }

    public void signout(View view){
     AuthUI.getInstance().signOut(this);

    }

    @Override
    protected void onStart() {
        super.onStart();
        FirebaseAuth.getInstance().addAuthStateListener(this);
    }

    @Override
    protected void onStop() {
        super.onStop();
        FirebaseAuth.getInstance().removeAuthStateListener(this);
    }

    @Override
    public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
        if (firebaseAuth.getCurrentUser() == null){
            startLogin();
            return;
        }
        firebaseAuth.getCurrentUser().getIdToken(true)
                .addOnSuccessListener(new OnSuccessListener<GetTokenResult>() {
                    @Override
                    public void onSuccess(GetTokenResult getTokenResult) {
                        Log.d(TAG, "onSuccess: "+getTokenResult.getToken());
                    }
                });
    }
}

Answer 1

I will suggest you that you create a splash screen (startup screen) which will initially on start check for the authentication whether user is logged in or not from the server. All this will be handled in a background thread and the ui thread will carry on the splash screen animation(if you wish any).So if the user is logged in, you navigate to mainActivity else navigate to loginActivity. Hope this helps you.