import android.content.Intent; import android.os.Bundle; import android.support.v7.app.AppCompatActivity; import android.view.View; import android.view.View.OnClickListener; import android.widget.TextView; import com.google.firebase.auth.FirebaseAuth; import com.google.firebase.auth.FirebaseUser; public class MainActivity extends AppCompatActivity { private FirebaseAuth mAuth; private TextView mTvEmail, mTvLogout; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); mAuth = FirebaseAuth.getInstance(); mTvLogout = findViewById(R.id.txtBtnLogout); mTvEmail = findViewById(R.id.tvEmail); FirebaseUser currentUser = mAuth.getCurrentUser(); if (currentUser == null) { //No one signed in startActivity(new Intent(this, SignInActivity.class)); this.finish(); }else{ //User logged in mTvEmail.setText(currentUser.getEmail()); } mTvLogout.setOnClickListener(new OnClickListener() { @Override public void onClick(View view) { mAuth.signOut(); startActivity(new Intent(MainActivity.this, SignInActivity.class)); MainActivity.this.finish(); } }); } }