使用底部導航欄從一個片段移動到另一個片段時重置數據

Question

我在我的項目中使用底部導航欄和片段。 當它從一個片段移動到另一個片段時，我不想丟失 state 或數據我該怎么做？

這是 activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <androidx.coordinatorlayout.widget.CoordinatorLayout
        android:id="@+id/container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="#F9FAFD">

        <FrameLayout
            android:id="@+id/page_fragment"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />
    </androidx.coordinatorlayout.widget.CoordinatorLayout>

    <com.google.android.material.bottomnavigation.BottomNavigationView
        android:id="@+id/bottom_bar"
        android:layout_width="match_parent"
        android:layout_height="56dp"
        android:layout_alignParentBottom="true"
        android:background="@android:color/white"
        app:labelVisibilityMode="labeled"
        app:menu="@menu/bottom_menu" />

</RelativeLayout>

這是 MainActivity.java

package com.noval.tugas_6;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.fragment.app.Fragment;

import android.os.Bundle;
import android.view.MenuItem;
import android.widget.Toast;

import com.google.android.material.bottomnavigation.BottomNavigationView;
import com.noval.tugas_6.computer.ComputerFragment;
import com.noval.tugas_6.home.HomeFragment;
import com.noval.tugas_6.home_services.HomeServicesFragment;
import com.noval.tugas_6.phone.PhoneFragment;

public class MainActivity extends AppCompatActivity {

    BottomNavigationView bottomNavigationView;
    private Fragment fragment;
    private long exitTime = 0;

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

        bottomNavigationView = findViewById(R.id.bottom_bar);
        getFragmentPage(new HomeFragment());
        setBottomNavigationView();
    }

    private void setBottomNavigationView() {
        bottomNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(@NonNull MenuItem item) {
                fragment = null;
                switch (item.getItemId()) {
                    //id yang ada di menu bottom_menu.xml
                    case R.id.home_menu:
                        fragment = new HomeFragment();
                        break;
                    case R.id.computer_menu:
                        fragment = new ComputerFragment();
                        break;
                    case R.id.phone_menu:
                        fragment = new PhoneFragment();
                        break;
                    case R.id.home_services_menu:
                        fragment = new HomeServicesFragment();
                        break;
                }
                return getFragmentPage(fragment);
            }
        });
    }

    private boolean getFragmentPage(Fragment fragment) {
        if (fragment != null) {
            getSupportFragmentManager()
                    .beginTransaction()
                    .setReorderingAllowed(true)
                    .addToBackStack(null)
                    .replace(R.id.page_fragment, fragment)
                    .commit();
            return true;
        }
        return false;
    }

    @Override
    public void onBackPressed() {

        if ((System.currentTimeMillis() - exitTime) > 2000) {
            Toast.makeText(this, "Press again to exit", Toast.LENGTH_SHORT).show();
            exitTime = System.currentTimeMillis();
        } else {
            finish();
            System.exit(0);
        }
    }
}

這是我正在使用 PhoneFragment.java 的片段之一

package com.noval.tugas_6.phone;

import android.os.Bundle;

import androidx.fragment.app.Fragment;

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;

import com.noval.tugas_6.R;

public class PhoneFragment extends Fragment {

    public int[] imgID = new int[]{R.drawable.infinix_zero, R.drawable.realme_c35,
            R.drawable.galaxy_a33, R.drawable.samsung_galaxy_a13, R.drawable.samsung_galaxy_a23};
    public String[] namaHP = new String[]{"Infinix Zero 5G", "Realme C35", "Samsung Galaxy A33 5G",
            "Samsung Galaxy A13", "Samsung Galaxy A23"};
    public String[] hargaHP = new String[]{"Rp3.600.000", "Rp2.150.000", "Rp4.700.000", "Rp2.500.000", "Rp3.500.000"};

    ImageView imgHP;
    TextView txtNama, txtHarga;
    Button btnNext, btnPrevious;
    int position = 0;

    public PhoneFragment() {
        // Required empty public constructor
    }

//    public static PhoneFragment newInstance() {
//        PhoneFragment fragment = new PhoneFragment();
//        Bundle args = new Bundle();
//        fragment.setArguments(args);
//        return fragment;
//    }
//
//    @Override
//    public void onCreate(Bundle savedInstanceState) {
//        super.onCreate(savedInstanceState);
//        if (getArguments() != null) {
//
//        }
//    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_phone, container, false);

    }

    // method ini dipanggil sesaat setelah onCreateView di atas dipanggil
    // semua pembacaan view dan penambahan listener dilakukan disini
    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        imgHP = (ImageView) getActivity().findViewById(R.id.imgHP);
        txtNama = (TextView) getActivity().findViewById(R.id.txtNamaHP);
        txtHarga = (TextView) getActivity().findViewById(R.id.txtHargaHP);
        btnNext = (Button) getActivity().findViewById(R.id.btnNextHP);
        btnPrevious = (Button) getActivity().findViewById(R.id.btnPreviousHP);

        imgHP.setImageResource(imgID[position]);
        txtNama.setText(namaHP[position]);
        txtHarga.setText(hargaHP[position]);
        btnPrevious.setVisibility(View.GONE);

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

                position += 1;
                imgHP.setImageResource(imgID[position]);
                txtNama.setText(namaHP[position]);
                txtHarga.setText(hargaHP[position]);

                // jika posisi item yang terakhir, hilangkan tombol next
                if (position == (imgID.length - 1)) {
                    btnNext.setVisibility(View.GONE);
                } else if (position > 0) {
                    btnPrevious.setVisibility(View.VISIBLE);
                }
            }
        });

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

                position -= 1;
                imgHP.setImageResource(imgID[position]);
                txtNama.setText(namaHP[position]);
                txtHarga.setText(hargaHP[position]);

                if (position == 0) {
                    btnPrevious.setVisibility(View.GONE);
                } else {
                    btnNext.setVisibility(View.VISIBLE);
                }
            }
        });
    }
}

請告訴我如何在移動到另一個片段時不丟失片段數據謝謝

Answer 1

因為每次用戶點擊導航底部時，你每次都會創建新的片段實例：

 private void setBottomNavigationView() {
    bottomNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
        @Override
        public boolean onNavigationItemSelected(@NonNull MenuItem item) {
            fragment = null;
            switch (item.getItemId()) {
                //id yang ada di menu bottom_menu.xml
                case R.id.home_menu:
                    fragment = new HomeFragment();
                    break;
                case R.id.computer_menu:
                    fragment = new ComputerFragment();
                    break;
                case R.id.phone_menu:
                    fragment = new PhoneFragment();
                    break;
                case R.id.home_services_menu:
                    fragment = new HomeServicesFragment();
                    break;
            }
            return getFragmentPage(fragment);
        }
    });
}

嘗試這個：

   private homeFragment = new HomeFragment();
private computerFragment = new ComputerFragment();
private phoneFragment = new PhoneFragment();
private homeServicesFragment = new HomeServicesFragment();
private Fragment active;
private final FragmentManager fm = getSupportFragmentManager();

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    ...
    initFragment();
    ...
}

private void changeFragment(Fragment fragment, Bundle bundle) {
    fm.beginTransaction()
            .hide(active)
            .show(fragment)
            .commit();
    active = fragment;
    active.setArguments(bundle);
}

private void initFragment() {
    fm.beginTransaction().add(R.id.frameLayout, homeFragment, homeFragment.class.getSimpleName()).commit();
    fm.beginTransaction().add(R.id.frameLayout, computerFragment, computerFragment.class.getSimpleName()).hide(computerFragment).commit();
    fm.beginTransaction().add(R.id.frameLayout, phoneFragment, PhoneFragment.class.getSimpleName()).hide(phoneFragment).commit();
    fm.beginTransaction().add(R.id.frameLayout, homeServicesFragment, HomeServicesFragment.class.getSimpleName()).hide(homeServicesFragment).commit();
     active = homeFragment;
    changeFragment(homeFragment, null);
}

private void setBottomNavigationView() {
    bottomNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
        @Override
        public boolean onNavigationItemSelected(@NonNull MenuItem item) {
            fragment = null;
            switch (item.getItemId()) {
                //id yang ada di menu bottom_menu.xml
                case R.id.home_menu:
                    changeFragment(homeFragment, null);
                    return true;
                     
                case R.id.computer_menu:
                    changeFragment(computerFragment, null);
                    return true;
                     
                case R.id.phone_menu:
                    changeFragment(phoneFragment, null);
                    return true;
                     
                case R.id.home_services_menu:
                    changeFragment(homeServicesFragment, null);
                    return true;
                     
            }
            return homeFragment;
        }
    });
}