我一直在尝试让我的Android应用程序能够在片段之间切换时保留您在片段中所做的操作。我希望能够在片段之间切换，而无需重新创建或替换它们，只需显示和隐藏它们。例如，如果您选中片段1中的一个框，但切换到片段2，然后返回片段1，我试着实现了这篇来自@Tester101 How can I switch between two fragments, without recreating the fragments each time?的文章中概述的解决方案
但是我不确定我是否让它正常工作。当我从HomeFragment切换到WidgetFragment时，WidgetFragment被放置在HomeFragment的顶部。
HomeFragment看起来像这样：x1c 0d1x但是当我切换到WidgetFragment时，它看起来像这样：

将WidgetFragment中的textview和复选框放在HomeFragment的顶部。

package loon.si.weather_app;

import androidx.annotation.NonNull;
import androidx.appcompat.app.ActionBarDrawerToggle;
import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;
import androidx.core.view.GravityCompat;
import androidx.drawerlayout.widget.DrawerLayout;
import androidx.fragment.app.FragmentManager;
import android.annotation.SuppressLint;
import android.os.Bundle;
import android.view.MenuItem;

import com.google.android.material.navigation.NavigationView;

import java.util.Objects;

public class MainActivity extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener {
    
    private DrawerLayout drawerLayout;

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

        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        
        drawerLayout = findViewById(R.id.drawer_layout);
        NavigationView navigationView = findViewById(R.id.nav_view);
        navigationView.setNavigationItemSelectedListener(this);

        ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(this, drawerLayout, toolbar, R.string.open_nav, R.string.close_nav);

        drawerLayout.addDrawerListener(toggle);
        toggle.syncState();

        if (savedInstanceState == null) {
            getSupportFragmentManager().beginTransaction()
                    .replace(R.id.fragment_container, new HomeFragment()).commit();
            navigationView.setCheckedItem(R.id.nav_home);
        }

    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        FragmentManager fragmentManager = getSupportFragmentManager();
        if(fragmentManager.findFragmentById(R.id.nav_home) != null){
            fragmentManager.beginTransaction().remove(Objects.requireNonNull(fragmentManager.findFragmentById(R.id.nav_home))).commit();
        }
        if(fragmentManager.findFragmentById(R.id.nav_widget) != null){
            fragmentManager.beginTransaction().remove(Objects.requireNonNull(fragmentManager.findFragmentById(R.id.nav_widget))).commit();
        }
    }

    @SuppressLint("NonConstantResourceId")
    @Override
    public boolean onNavigationItemSelected(@NonNull MenuItem item) {
        FragmentManager fragmentManager = getSupportFragmentManager();
        switch (item.getItemId()){
            case R.id.nav_home:
                if(fragmentManager.findFragmentById(R.id.nav_home) != null) {
                    //if the fragment exists, show it.
                    fragmentManager.beginTransaction().show(Objects.requireNonNull(fragmentManager.findFragmentById(R.id.nav_home))).commit();
                } else {
                    //if the fragment does not exist, add it to fragment manager.
                    fragmentManager.beginTransaction().add(R.id.fragment_container, new HomeFragment(), "home").commit();
                }
                if(fragmentManager.findFragmentById(R.id.nav_widget) != null){
                    //if the other fragment is visible, hide it.
                    fragmentManager.beginTransaction().hide(Objects.requireNonNull(fragmentManager.findFragmentById(R.id.nav_widget))).commit();
                }
                break;

            case R.id.nav_widget:
                if(fragmentManager.findFragmentById(R.id.nav_widget) != null) {
                    //if the fragment exists, show it.
                    fragmentManager.beginTransaction().show(Objects.requireNonNull(fragmentManager.findFragmentById(R.id.nav_widget))).commit();
                } else {
                    //if the fragment does not exist, add it to fragment manager.
                    fragmentManager.beginTransaction().add(R.id.fragment_container, new WidgetFragment(), "widget").commit();
                }
                if(fragmentManager.findFragmentById(R.id.nav_home) != null){
                    //if the other fragment is visible, hide it.
                    fragmentManager.beginTransaction().hide(Objects.requireNonNull(fragmentManager.findFragmentById(R.id.nav_home))).commit();
                }
                break;
        }
        drawerLayout.closeDrawer(GravityCompat.START);
        return true;
    }

    @Override
    public void onBackPressed() {
        if (drawerLayout.isDrawerOpen(GravityCompat.START)){
            drawerLayout.closeDrawer(GravityCompat.START);
        } else {
            super.onBackPressed();
        }
    }
}