使用导航主机在底部导航中停止片段刷新 [英] Stop fragment refresh in bottom nav using navhost

问题描述

这个问题已经被问过几次了，但我们现在是 2020 年，有没有人找到一个好的可用的解决方案?

This problem has been asked a few times now, but we are in 2020 now, did anyone find a good usable solution to this yet?

我希望能够使用底部导航控件进行导航，而无需在每次选择片段时刷新它们.这是我目前拥有的:

I want to be able to navigate using the bottom navigation control without refreshing the fragment each time they are selected. Here is what I have currently:

导航/main.xml:

navigation/main.xml:

<?xml version="1.0" encoding="utf-8"?>
<navigation 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:id="@+id/main"
    app:startDestination="@id/home">

    <fragment
        android:id="@+id/home"
        android:name="com.org.ftech.fragment.HomeFragment"
        android:label="@string/app_name"
        tools:layout="@layout/fragment_home" />
    <fragment
        android:id="@+id/news"
        android:name="com.org.ftech.fragment.NewsFragment"
        android:label="News"
        tools:layout="@layout/fragment_news"/>
    <fragment
        android:id="@+id/markets"
        android:name="com.org.ftech.fragment.MarketsFragment"
        android:label="Markets"
        tools:layout="@layout/fragment_markets"/>
    <fragment
        android:id="@+id/explore"
        android:name="com.org.ftech.ExploreFragment"
        android:label="Explore"
        tools:layout="@layout/fragment_explore"/>
</navigation>

activity_mail.xml:

activity_mail.xml:

<?xml version="1.0" encoding="utf-8"?>
<!-- Use DrawerLayout as root container for activity -->
<androidx.drawerlayout.widget.DrawerLayout
    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:id="@+id/drawer_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <fragment
            android:id="@+id/nav_host_fragment"
            android:name="androidx.navigation.fragment.NavHostFragment"
            android:layout_width="0dp"
            android:layout_height="0dp"
            app:defaultNavHost="true"
            app:layout_constraintBottom_toTopOf="@+id/bottomNavigationView"
            app:layout_constraintHorizontal_bias="0.0"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            app:navGraph="@navigation/main" />

        <com.google.android.material.bottomnavigation.BottomNavigationView
            android:id="@+id/bottomNavigationView"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:itemIconTint="@color/nav"
            app:itemTextColor="@color/nav"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintHorizontal_bias="0.0"
            app:layout_constraintStart_toStartOf="parent"
            app:menu="@menu/main">

        </com.google.android.material.bottomnavigation.BottomNavigationView>

    </androidx.constraintlayout.widget.ConstraintLayout>

    <com.google.android.material.navigation.NavigationView
        app:menu="@menu/main"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:id="@+id/navigationView"
        android:layout_gravity="start">
    </com.google.android.material.navigation.NavigationView>

</androidx.drawerlayout.widget.DrawerLayout>

MainActivity.kt:

MainActivity.kt:

class MainActivity : AppCompatActivity() {

    private var drawerLayout: DrawerLayout? = null
    private var navigationView: NavigationView? = null
    private var bottomNavigationView: BottomNavigationView? = null
    private lateinit var appBarConfiguration: AppBarConfiguration

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        drawerLayout = findViewById(R.id.drawer_layout)
        navigationView = findViewById(R.id.navigationView)
        bottomNavigationView = findViewById(R.id.bottomNavigationView)

        val navController = findNavController(R.id.nav_host_fragment)
        appBarConfiguration = AppBarConfiguration(setOf(R.id.markets, R.id.explore, R.id.news, R.id.home), drawerLayout)

        setupActionBarWithNavController(navController, appBarConfiguration)

        findViewById<NavigationView>(R.id.navigationView)
            .setupWithNavController(navController)

        findViewById<BottomNavigationView>(R.id.bottomNavigationView)
            .setupWithNavController(navController)

    }


    override fun onSupportNavigateUp(): Boolean {
        val navController = findNavController(R.id.nav_host_fragment)
        return navController.navigateUp(appBarConfiguration) || super.onSupportNavigateUp()
    }

    override fun onOptionsItemSelected(item: MenuItem): Boolean {
        if (item.itemId == R.id.search) {
            startActivity(Intent(applicationContext, SearchableActivity::class.java))
        }
        return super.onOptionsItemSelected(item)
    }

    override fun onCreateOptionsMenu(menu: Menu?): Boolean {
        menuInflater.inflate(R.menu.options_menu, menu)
        return super.onCreateOptionsMenu(menu)
    }
}

在片段中，我对我的服务进行了几次调用以获取 onCreateView 中的数据，当恢复片段时，我假设这些调用将不再被执行，并且片段的状态应该保存.

In the fragment I am making a few calls to my services to fetch the data in onCreateView, when resuming the fragment I am assuming those calls will not longer be executed and the state of the fragment should be preserved.

推荐答案

试试这个:

public class MainActivity extends AppCompatActivity {


    final Fragment fragment1 = new HomeFragment();
    final Fragment fragment2 = new DashboardFragment();
    final Fragment fragment3 = new NotificationsFragment();
    final FragmentManager fm = getSupportFragmentManager();
    Fragment active = fragment1;

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

        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);


        BottomNavigationView navigation = (BottomNavigationView) findViewById(R.id.navigation);
        navigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);

        fm.beginTransaction().add(R.id.main_container, fragment3, "3").hide(fragment3).commit();
        fm.beginTransaction().add(R.id.main_container, fragment2, "2").hide(fragment2).commit();
        fm.beginTransaction().add(R.id.main_container,fragment1, "1").commit();

    }


    private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener
            = new BottomNavigationView.OnNavigationItemSelectedListener() {

        @Override
        public boolean onNavigationItemSelected(@NonNull MenuItem item) {
            switch (item.getItemId()) {
                case R.id.navigation_home:
                    fm.beginTransaction().hide(active).show(fragment1).commit();
                    active = fragment1;
                    return true;

                case R.id.navigation_dashboard:
                    fm.beginTransaction().hide(active).show(fragment2).commit();
                    active = fragment2;
                    return true;

                case R.id.navigation_notifications:
                    fm.beginTransaction().hide(active).show(fragment3).commit();
                    active = fragment3;
                    return true;
            }
            return false;
        }
    };


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main_menu, menu);
        return super.onCreateOptionsMenu(menu);
    }
    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int id = item.getItemId();

        if (id == R.id.action_settings) {
            startActivity(new Intent(MainActivity.this, SettingsActivity.class));
            return true;
        }

        return super.onOptionsItemSelected(item);
    }


}

或者您可以遵循 Google 推荐的解决方案:Google 链接

Or You can follow Google's recommended solution: Google Link

这篇关于使用导航主机在底部导航中停止片段刷新的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！