在新的导航抽屉活动模板中使用onNavigationItemSelected在片段之间切换(Android Studio 1.4以后)

Question

IntelliJ在Android Studio中对Navigation Drawer模板Activity进行了更改,Activity类中的代码行更少.新的Activity类如下所示:

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);

    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                    .setAction("Action", null).show();
        }
    });

    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);
}

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


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

    if (id == R.id.nav_camara) {
        // Handle the camera action
    } else if (id == R.id.nav_gallery) {

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

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

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

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

    }

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

这里最显着的变化之一是方法:

onNavigationItemSelected(MenuItem item)

旧的Navigation Drawer模板对此方法的定义是:

onNavigationItemSelected(int position, long itemId)

您可以通过删除内部PlaceHolderFragment类来修改该旧模板,创建自己的片段和布局,并执行以下操作:

Fragment fragment = null;
switch (position) {
    case 0:
        fragment = new FragmentA();
        break;
    case 1:
        fragment = new FragmentB();
        break;
    default:
        break;
}

if (fragment != null) {
    FragmentManager fragmentManager = getSupportFragmentManager();
    fragmentManager.beginTransaction()
            .replace(R.id.frame_container, fragment).commit();

}

但这不适用于新模板(至少不是我的小知识).我试过了:

 public boolean onNavigationItemSelected(MenuItem item) {
    // Handle navigation view item clicks here.
    int id = item.getItemId();
    Snackbar snackbar = Snackbar.make(findViewById(android.R.id.content), item.getTitle() + " clicked", Snackbar.LENGTH_SHORT);
    Fragment fragment = null;
    switch (id) {
        case R.id.nav_home:
            fragment = HomeFragment.getFragInstance();
            break;

        case R.id.nav_news:

            fragment = NewsFragment.getFragInstance();
            break;


        default:
            break;
    }

    if (fragment != null) {
        FragmentTransaction transaction = fragmentManager.beginTransaction();
        transaction.addToBackStack(null);
        transaction.replace(R.id.drawer_layout, fragment);
        transaction.commit();


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

    }
    return true;
}

但布局的home布局也显示在news布局中.这可能是因为这条线:

transaction.replace(R.id.drawer_layout, fragment);

片段应该在a中替换,FrameLayout旧的Navigation Drawer布局如下所示:

<android.support.v4.widget.DrawerLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent">

<!-- Framelayout to display Fragments -->
<FrameLayout
    android:id="@+id/frame_container"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

<!-- Listview to display slider menu -->


<ListView
    android:id="@+id/list_sliderMenu"
    android:layout_width="240dp"
    android:layout_height="match_parent"
    android:layout_gravity="start"
    android:choiceMode="singleChoice"
    android:divider="@color/white"
    android:dividerHeight="1dp"
    android:listSelector="@drawable/list_selector"
    android:background="@color/list_background"/>

但新的看起来像这样:

 <?xml version="1.0" encoding="utf-8"?>
  <android.support.v4.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_base"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

<android.support.design.widget.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_base"
    app:menu="@menu/activity_base_drawer" />

    </android.support.v4.widget.DrawerLayout>

长话短说,如何修改新模板才能在片段之间切换？

Answer 1

所以,基于@LL的答案,我能够解决这个问题.

首先,将FrameLayout添加到您的content_main.xml文件中:

<FrameLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent" android:id="@+id/content_frame"/>

在您MainActivity(或任何您使用导航抽屉命名的活动)中,定义一个名为的方法displayView

 public void displayView(int viewId) {

    Fragment fragment = null;
    String title = getString(R.string.app_name);

    switch (viewId) {
        case R.id.nav_news:
            fragment = new NewsFragment();
            title  = "News";

            break;
        case R.id.nav_events:
            fragment = new EventsFragment();
            title = "Events";
            break;

    }

    if (fragment != null) {
        FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
        ft.replace(R.id.content_frame, fragment);
        ft.commit();
    }

    // set the toolbar title
    if (getSupportActionBar() != null) {
        getSupportActionBar().setTitle(title);
    }

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

}

我在3个自定义碎片之间切换; NewsFragment,EventsFragment和GalleryFragment.

在我的菜单中,activity_main_drawer我已将内容更改为:

<menu xmlns:android="http://schemas.android.com/apk/res/android">

<group android:checkableBehavior="single">
    <item android:id="@+id/nav_news"  
        android:icon="@android:drawable/ic_menu_news"
        android:title="News" />
    <item android:id="@+id/nav_events" 
        android:icon="@android:drawable/ic_menu_events"
        android:title="Events" />
    <item android:id="@+id/nav_gallery" 
        android:icon="@android:drawable/ic_menu_gallery"
        android:title="Gallery" />
  </group>
</menu>

回到Activity类,在你的onNavigationItemSelected方法中执行以下操作:

@Override
public boolean onNavigationItemSelected(MenuItem item) {
    displayView(item.getItemId());
    return true;
}

最后,你的onCreate方法中的最后一个语句:

 @Override
protected void onCreate(Bundle savedInstanceState) {
    ....
    ....
    displayView(R.id.nav_news);
}

这是因为我希望我的用户看到的第一个视图是News.Change它为您选择的任何内容.

处理新闻事件:

现在,如果您按下任何片段中的后退按钮,应用程序将退出.当用户按下后退按钮时,我希望我的应用程序返回到新闻片段(我的主片段).所以我这样做了:

声明了一个布尔变量:

private boolean viewIsAtHome;

然后在displayView()方法中我做了这个:

 public void displayView(int viewId){
    Fragment fragment = null;
    String title = getString(R.string.app_name);

    switch (viewId) {
        case R.id.nav_news:
            fragment = new NewsFragment();
            title  = getString(R.string.news_title);
            viewIsAtHome = true;

            break;
        case R.id.nav_events:
            fragment = new EventsFragment();
            title = getString(R.string.events_title);
            viewIsAtHome = false;
            break;

        case R.id.nav_gallery:
            fragment = new GalleryFragment();
            title = getString(R.string.gallery_title);
            viewIsAtHome = false;
            break;

最后,删除旧onBackPressed方法并在方法外创建一个新onCreate()方法:

@Override
public void onBackPressed() {
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    if (drawer.isDrawerOpen(GravityCompat.START)) {
        drawer.closeDrawer(GravityCompat.START);
    }
    if (!viewIsAtHome) { //if the current view is not the News fragment
        displayView(R.id.nav_news); //display the News fragment
    } else {
        moveTaskToBack(true);  //If view is in News fragment, exit application
    }
}

适合我.

Answer 2

你不应该改变DrawerLayout,你只需要在"content_main.xml"中添加一个框架.

请按照以下步骤操作:

1. 打开位于"layout"文件夹中的"content_main.xml"文件.

2. 使用以下代码:

   <?xml version="1.0" encoding="utf-8"?> 
   <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
       xmlns:tools="http://schemas.android.com/tools"
       xmlns:app="http://schemas.android.com/apk/res-auto" android:layout_width="match_parent"
       android:layout_height="match_parent"
       app:layout_behavior="@string/appbar_scrolling_view_behavior" tools:showIn="@layout/app_bar_main"
       tools:context=".MainActivity">    
       <FrameLayout
           android:layout_width="match_parent"
           android:layout_height="match_parent" android:id="@+id/mainFrame">
       </FrameLayout>   
   </RelativeLayout>
   

3. 转到onNavigationItemSelected方法:

   public boolean onNavigationItemSelected(MenuItem item) {
     int id = item.getItemId();
     Fragment fragment;
   
   if (id == R.id.nav_camara) {
       fragment = new YourFragment();
       FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
       ft.replace(R.id.mainFrame, fragment);
       ft.commit();
   }
   else if (id == R.id.nav_gallery) {
   
   }
   else if (id == R.id.nav_slideshow) {
   
   }
   else if (id == R.id.nav_manage) {
   
   } else if (id == R.id.nav_share) {
   
   } else if (id == R.id.nav_send) {
   
   }
   
   DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
   drawer.closeDrawer(GravityCompat.START);
   return true;
   }