后按Xamarin Android

Question

Hy Everybody,

I trying to use OnKeyDown in my app, but i trying to use inside a fragment, what happens... i have a Activity in this Activity, i have a Fragments that invoke others fragments and when a press back button, the app close... how can i implemente it? Can someone give a example?

namespace Uer.Fragments
{
    public class Login : Fragment
    {
        //Statement Objects
        private TextView lblNewUser;
        private LinearLayout lnlContainer;
        private EditText edtEmail;
        private EditText edtPassword;
        private Button btnLogin;

        public override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);

            // Create your fragment here
        }

        public override View OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
        {
            // Use this to return your custom view for this Fragment
            View view = inflater.Inflate(Resource.Layout.Login, container, false);

            lnlContainer = view.FindViewById<LinearLayout>(Resource.Id.lnlContainer);
            lblNewUser = view.FindViewById<TextView>(Resource.Id.lblNewUser);
            edtEmail = view.FindViewById<EditText>(Resource.Id.edtEmail);
            edtPassword = view.FindViewById<EditText>(Resource.Id.edtPassword);
            btnLogin = view.FindViewById<Button>(Resource.Id.btnLogin);

            lblNewUser.Click += LblNewUser_Click;
            btnLogin.Click += BtnLogin_Click;
            return view;            
        }

        private void BtnLogin_Click(object sender, EventArgs e)
        {
            string email = edtEmail.Text;
            string password = edtPassword.Text;

            if (string.IsNullOrEmpty(email) || string.IsNullOrEmpty(password))
            {
                AlertDialog.Builder alert = new AlertDialog.Builder(Activity);
                alert.SetTitle("Campos Vazios");
                alert.SetMessage("Email ou Senha estao vazios");
                alert.SetNeutralButton("OK", (senderAlert, args) =>
                {
                    alert.Dispose();
                });
                alert.Create();
                alert.Show();

            } else if (!email.Equals("uer@uer.com") || !password.Equals("admin"))
            {
                AlertDialog.Builder alert = new AlertDialog.Builder(Activity);
                alert.SetTitle("Email ou Senha Invalidos");
                alert.SetMessage("Voce digitou email ou senha incorreto");
                alert.SetNeutralButton("OK", (senderAlert, args) =>
                {
                    alert.Dispose();
                });
                alert.Create();
                alert.Show();
            }
            else
            {
                Intent intent = new Intent(Activity, typeof(MainActivity));
                this.StartActivity(intent);
            }
        }

        private void LblNewUser_Click(object sender, EventArgs e)
        {
            var transaction = Activity.SupportFragmentManager.BeginTransaction();
            transaction.SetCustomAnimations(Resource.Animation.slide_in,
                Resource.Animation.slide_out, Resource.Animation.slide_in,
                Resource.Animation.slide_out);
            transaction.Replace(Resource.Id.lnlContainer, new Register(), "Register");
            transaction.Commit();
            //Intent intent = new Intent(Activity, typeof(RegisterActivity));
            //this.StartActivity(intent);
        }
    }
}

Answer 1

When you are transitioning between Fragments , call addToBackStack() :

FragmentTransaction FragmentTransaction tx = fragmentManager.beginTransation(); 
tx.replace( R.id.fragment, new MyFragment() ).addToBackStack( "tag" ).commit();