单击项目后，我需要输入什么代码以及在哪里切换到不同的片段？

Question

在我的 activity_main_drawer 上，我有很多项目，但我不知道为切换片段添加什么代码以及添加到哪里

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    tools:showIn="navigation_view">

    <group android:checkableBehavior="single">
        <item
            android:id="@+id/nav_contests"
            android:icon="@drawable/ic_menu_camera"
            android:title="@string/menu_home" />
        <item
            android:id="@+id/nav_rules"
            android:icon="@drawable/irules"
            android:title="@string/box_contest_rules" />
        <item
            android:id="@+id/nav_profile"
            android:icon="@drawable/ic_baseline_face_24"
            android:title="@string/profile_page" />
        <item
            android:id="@+id/nav_calendar"
            android:icon="@drawable/icalendar"
            android:title="@string/calendar_page" />
        <item
            android:id="@+id/nav_gallery"
            android:icon="@drawable/igallery"
            android:title="@string/gallery_page" />
        <item
            android:id="@+id/nav_stats"
            android:icon="@drawable/istats"
            android:title="@string/stats_page" />
        <item
            android:id="@+id/nav_rank"
            android:icon="@drawable/irank"
            android:title="@string/rank_page" />
        <item
            android:id="@+id/nav_shop"
            android:icon="@drawable/ishop"
            android:title="@string/shop_page" />
        <item
            android:id="@+id/nav_setting"
            android:icon="@drawable/ic_baseline_settings_24"
            android:title="@string/setting_page" />
    </group>
</menu>

这是 java 主页，我正在努力了解要添加代码的位置和内容

public class HomePage extends AppCompatActivity {
    private AppBarConfiguration mAppBarConfiguration;

    @SuppressLint("WrongViewCast")
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_home_page);
        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        DrawerLayout drawer = findViewById(R.id.drawer_layout);
        NavigationView navigationView = findViewById(R.id.nav_view);
        // Passing each menu ID as a set of Ids because each
        // menu should be considered as top level destinations.
        mAppBarConfiguration = new AppBarConfiguration.Builder(
                R.id.nav_home, R.id.nav_gallery, R.id.nav_slideshow)
                .setDrawerLayout(drawer)
                .build();
        NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment);
        NavigationUI.setupActionBarWithNavController(this, navController, mAppBarConfiguration);
        NavigationUI.setupWithNavController(navigationView, navController);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.home_page, menu);
        return true;
    }

    @Override
    public boolean onSupportNavigateUp() {
        NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment);
        return NavigationUI.navigateUp(navController, mAppBarConfiguration)
                || super.onSupportNavigateUp();
    }
}

这是片段之一 java 作为示例。

public class GalleryFragment extends Fragment {

    private GalleryViewModel galleryViewModel;

    public View onCreateView(@NonNull LayoutInflater inflater,
                             ViewGroup container, Bundle savedInstanceState) {
        galleryViewModel =
                ViewModelProviders.of(this).get(GalleryViewModel.class);
        View root = inflater.inflate(R.layout.fragment_gallery, container, false);
        final TextView textView = root.findViewById(R.id.text_gallery);
        galleryViewModel.getText().observe(getViewLifecycleOwner(), new Observer<String>() {
            @Override
            public void onChanged(@Nullable String s) {
                textView.setText(s);
            }
        });
        return root;
    }
}

从 HomePage 切换到 GalleryFragment 并返回的示例会很棒

Answer 1

尝试-->

将其放入您的主要活动中：-

@Override
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();

if (id == R.id.nav_contests) {
//intent to next activity


} else if (id == R.id.nav_rules) {
 //just an example
 String message = "Text I want to share.";
 Intent share = new Intent(Intent.ACTION_SEND);
 share.setType("text/plain");
share.putExtra(Intent.EXTRA_TEXT, message);

startActivity(Intent.createChooser(share, "Title of the dialog the system will open"));


} else if (id == R.id.nav_profile) {

 ///your actions
}
} else if (id == R.id.nav_calendar) {

}
 } else if (id == R.id.nav_gallery) {

}
} else if (id == R.id.nav_stats) {

}




DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}

演示

main_activity:

package ijsolutions.appnav;

import android.os.Bundle;
 import androidx.core.view.GravityCompat;
 import androidx.appcompat.app.ActionBarDrawerToggle;
import android.view.MenuItem;
import com.google.android.material.navigation.NavigationView;
import androidx.drawerlayout.widget.DrawerLayout;
import androidx.appcompat.app.AppCompatActivity;
 import androidx.appcompat.widget.Toolbar;
 import androidx.fragment.app.Fragment;
 import androidx.fragment.app.FragmentTransaction;
 import android.view.Menu;

 public class MainActivity extends AppCompatActivity
    implements NavigationView.OnNavigationItemSelectedListener {
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
            this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
    drawer.setDrawerListener(toggle);
    toggle.syncState();

    NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
    navigationView.setNavigationItemSelectedListener(this);

    //add this line to display menu1 when the activity is loaded
    displaySelectedScreen(R.id.nav_home);
}

@Override
public void onBackPressed() {
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    if (drawer.isDrawerOpen(GravityCompat.START)) {
        drawer.closeDrawer(GravityCompat.START);
    } else {
        super.onBackPressed();
    }
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}


private void displaySelectedScreen(int itemId) {

    //creating fragment object
    Fragment fragment = null;
    FragmentTransaction ft = getSupportFragmentManager().beginTransaction();

    //initializing the fragment object which is selected
    switch (itemId) {
        case R.id.nav_home:
            fragment = new Menu1();
            //ft.addToBackStack(null);
            break;
        case R.id.nav_gallery:
            fragment = new Menu2();
            ft.addToBackStack(null);

            break;
        case R.id.nav_slideshow:
            fragment = new Menu3();
            ft.addToBackStack(null);

            break;

    }

    //replacing the fragment
    if (fragment != null) {
        ft.replace(R.id.content_frame, fragment);

        ft.commit();
    }

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    drawer.closeDrawer(GravityCompat.START);
}


@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {

    //calling the method displayselectedscreen and passing the id of selected menu
    displaySelectedScreen(item.getItemId());
    //make this method blank
    return true;
}}

菜单1

public class Menu1 extends Fragment {


public Menu1() {
    // Required empty public constructor
}


@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    return inflater.inflate(R.layout.fragment_menu1, container, false);
}

}

xml 菜单 1

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".Menu1"
android:background="#68a">

<!-- TODO: Update blank fragment layout -->
<TextView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:text="@string/Home"
    android:layout_marginLeft="60dp"
    android:textSize="50dp"
  />

所以我没有放其他菜单，因为它是一样的

activitymain xml

<?xml version="1.0" encoding="utf-8"?>
 <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"
android:fitsSystemWindows="true"
tools:openDrawer="start">

<include
    layout="@layout/app_bar_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

<com.google.android.material.navigation.NavigationView
    android:id="@+id/nav_view"
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    android:layout_gravity="start"
    android:fitsSystemWindows="true"
    app:headerLayout="@layout/nav_header_main"
    app:menu="@menu/activity_main_drawer" />

</androidx.drawerlayout.widget.DrawerLayout>

activity_main_drawer

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
tools:showIn="navigation_view">

<group android:checkableBehavior="single">
    <item
        android:id="@+id/nav_home"
        android:icon="@drawable/ic_menu_camera"
        android:title="@string/menu_home" />
    <item
        android:id="@+id/nav_gallery"
        android:icon="@drawable/ic_menu_gallery"
        android:title="@string/menu_gallery" />
    <item
        android:id="@+id/nav_slideshow"
        android:icon="@drawable/ic_menu_slideshow"
        android:title="@string/menu_slideshow" />
    <item
        android:id="@+id/nav_tools"
        android:icon="@drawable/ic_menu_manage"
        android:title="@string/menu_tools" />
</group>

<item android:title="Communicate">
    <menu>
        <item
            android:id="@+id/nav_share"
            android:icon="@drawable/ic_menu_share"
            android:title="@string/menu_share" />
        <item
            android:id="@+id/nav_send"
            android:icon="@drawable/ic_menu_send"
            android:title="@string/menu_send" />
    </menu>
</item>

main.xml

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">
<item
    android:id="@+id/action_settings"
    android:orderInCategory="100"
    android:title="@string/action_settings"
    app:showAsAction="never" />
 </menu>

content_main:

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 
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"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
tools:context=".MainActivity"
tools:showIn="@layout/app_bar_main">
<FrameLayout
    android:id="@+id/content_frame"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />
   </androidx.constraintlayout.widget.ConstraintLayout>

app_bar_main

<?xml version="1.0" encoding="utf-8"?>
 <androidx.coordinatorlayout.widget.CoordinatorLayout 
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">

<com.google.android.material.appbar.AppBarLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:theme="@style/AppTheme.AppBarOverlay">

    <androidx.appcompat.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        android:background="?attr/colorPrimary"
        app:popupTheme="@style/AppTheme.PopupOverlay" />

</com.google.android.material.appbar.AppBarLayout>

<include layout="@layout/content_main" />



 </androidx.coordinatorlayout.widget.CoordinatorLayout>

Answer 2

加你activity。有效

 @Override
    public boolean onNavigationItemSelected(MenuItem item) {

        int id = item.getItemId();

        if (id == R.id.nav_home) {

        }else if (id == R.id.nav_logout) {
            logOut(HomePage.this, "Logout due to nav. logout");
        }
        
        
        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        drawer.closeDrawer(GravityCompat.START);
        return true;
  }

单击项目后，我需要输入什么代码以及在哪里切换到不同的片段？

What code i need to input, and where, to switch to a different fragment once item is clicked?

java

android

fragment

drawer