public class SignIn extends AppCompatActivity {

EditText edtPhone,edtPassword;
Button btnSignIn;

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

    edtPassword = (MaterialEditText)findViewById(R.id.edtPassword);
    edtPhone = (MaterialEditText)findViewById(R.id.edtPhone);
    btnSignIn = (Button)findViewById(R.id.btnSignIn);

    //init firebase

    final FirebaseDatabase database = FirebaseDatabase.getInstance();
    final DatabaseReference table_user = database.getReference("Usuario");

    btnSignIn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

            final ProgressDialog mDialog = new ProgressDialog(SignIn.this);
            mDialog.setMessage("Por favor espera...");
            mDialog.show();


            table_user.addValueEventListener(new ValueEventListener() {





                @Override
                public void onDataChange(DataSnapshot dataSnapshot) {

                    //comprobar si el usuario no existe en la base de datos
                    if (dataSnapshot.child(edtPhone.getText().toString()).exists()) {

                        //Informacion usuario

                        mDialog.dismiss();
                        Usuario usuario = dataSnapshot.child(edtPhone.getText().toString()).getValue(Usuario.class);
                        if (usuario.getContraseña().equals(edtPassword.getText().toString())) {
                            Toast.makeText(SignIn.this, "Inicio de Sesión Exitoso !", Toast.LENGTH_SHORT).show();
                        } else {
                            Toast.makeText(SignIn.this, "Inicio de Sesión Fallido !!", Toast.LENGTH_SHORT).show();
                        }
                    }
                    else
                    {
                        Toast.makeText(SignIn.this, "Usuario no registrado en base de dato", Toast.LENGTH_SHORT).show();
                    }

                }

                @Override
                public void onCancelled(DatabaseError databaseError) {
                }
            });
        }
    });

}