java - 当我一直按后退按钮登录时，字段显示先前插入的用户数据

Question

我正在 Java 上制作一个 Android 应用程序。这个应用程序的问题是，当我在主 fragment 中并按后退按钮时，我希望它返回登录(这种情况发生)，但用户名和密码字段显示来自最后一个用户的数据，我想要这些字段显示为空，就像应用程序重新启动一样。

这是我的登录类中的登录用户函数。

public void loginUser() {

        String url = MeuSingleton.servidor + "/login";

        loginemail = email.getText().toString().trim();
        loginpass = pass.getText().toString().trim();

        StringRequest stringRequest = new StringRequest(Request.Method.POST, url,
                new Response.Listener<String>() {
                    @Override
                    public void onResponse(String response) {
                        try {
                            if (response.length() == 9){
                                Toast.makeText(Login.this, "Login efectuado com sucesso!", Toast.LENGTH_SHORT).show();
                                Intent i = new Intent(Login.this, MainActivity.class);
                                startActivity(i);
                            } else {
                                mostrarErro(getString(R.string.tituloerro), getString(R.string.login_errado));
                            }
                        } catch (Exception e) {
                            mostrarErro(getString(R.string.tituloerro), getString(R.string.backenderro));
                        }
                    }
                },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        mostrarErro(getString(R.string.tituloerro), getString(R.string.interneterro));
                    }
                }) {
            @Override
            protected Map<String, String> getParams() throws AuthFailureError {
                Map<String, String> map = new HashMap<String, String>();
                map.put("email", loginemail);
                map.put("password", loginpass);
                return map;
            }
        };
        MeuSingleton.getInstance(this).addToRequestQueue(stringRequest);
        stringRequest.setRetryPolicy(new DefaultRetryPolicy(350, DefaultRetryPolicy.DEFAULT_MAX_RETRIES, DefaultRetryPolicy.DEFAULT_BACKOFF_MULT));
    }

这是我的主要 Activity 类(class):

public class MainActivity extends AppCompatActivity implements
        NavigationView.OnNavigationItemSelectedListener{

    MainFragment mainFragment;
    FragmentManager fragmentManager;
    FragmentTransaction fragmentTransaction;
    DrawerLayout drawer;
    NavigationView navigationView;
    ActionBarDrawerToggle toggle;
    Toolbar toolbar;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        navigationView = findViewById(R.id.nested);
        navigationView.setNavigationItemSelectedListener(this);

        drawer = findViewById(R.id.drawer);
        toggle = new ActionBarDrawerToggle(this,drawer,toolbar,R.string.open,R.string.close);
        drawer.addDrawerListener(toggle);
        toggle.setDrawerIndicatorEnabled(true);
        toggle.syncState();

        mainFragment = new MainFragment();
        fragmentManager = getSupportFragmentManager();
        fragmentTransaction = fragmentManager.beginTransaction();
        fragmentTransaction.add(R.id.fragmentContainer,mainFragment);
        fragmentTransaction.commit();// add the fragment

    }

    @Override
    public boolean onNavigationItemSelected(@NonNull MenuItem menuItem) {
        closeDrawer();
        if(menuItem.getItemId() == R.id.submeteralerta){
            loadFragment(new InsAlertaFragment());
        }
        if(menuItem.getItemId() == R.id.veralertas){
            loadFragment(new SecondFragment());
        }
        if(menuItem.getItemId() == R.id.logout){
            finish();
        }
        if(menuItem.getItemId() == R.id.sobremim){
            loadFragment(new SobreMimFragment());
        }
        if(menuItem.getItemId() == R.id.ajuda){
            loadFragment(new AjudaFragment());
        }
        return true;
    }

    private void loadFragment(Fragment secondFragment) {
        fragmentManager = getSupportFragmentManager();
        fragmentTransaction = fragmentManager.beginTransaction();
        fragmentTransaction.replace(R.id.fragmentContainer,secondFragment);
        fragmentTransaction.addToBackStack(null);
        fragmentTransaction.commit();
    }

    private void closeDrawer() {
        drawer.closeDrawer(GravityCompat.START);
    }
}

最后是我的主要 fragment ，我想按回键并转到登录:

public class MainFragment extends Fragment {

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_main,container,false);
        return view;
    }

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
    }


}

感谢您的帮助!

Answer 1

如果您希望返回时具有空文本字段的登录 Activity ，您可以在启动 MainActivity 之前清除文本字段。例如:

Toast.makeText(Login.this, "Login efectuado com sucesso!", Toast.LENGTH_SHORT).show();
email.setText("");
pass.setText("");
Intent i = new Intent(Login.this, MainActivity.class);
startActivity(i);