android - 如何在底部導航視圖中設置菜單項？

Question

我有一個底部導航視圖及4個項目。

我希望在每個底部導航視圖按鈕的中間設置項目，我已經找到了一種方法，但它只在應用程序啓動時才起作用。

當我選擇另一個項目後，每個圖標向上移動，我不知道他們爲什麼不保留自己的位置。

public class MainActivity extends AppCompatActivity{ 
    private Toolbar mToolbar; 
    private BottomNavigationView bottomNavigationView; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 
     mToolbar = (Toolbar) findViewById(R.id.customToolbar); 
     setSupportActionBar(mToolbar); 
     setTitle(""); 
     mToolbar.setNavigationIcon(R.mipmap.back_icon); 

     bottomNavigationView = (BottomNavigationView) findViewById(R.id.bottom_navigation); 
     BottomNavigationViewShiftDisable.disableShiftMode(bottomNavigationView); 

     bottomNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() { 
      @Override 
      public boolean onNavigationItemSelected(@NonNull MenuItem item) { 
       Fragment fragment = null; 
       switch (item.getItemId()) { 
        case R.id.profile: 
         fragment = new FirstFragment(); 
         break; 
        case R.id.friends: 
         fragment = new SecondFragment(); 
         break; 
        case R.id.circle: 
         fragment = new ThirdFragment(); 
         break; 
        case R.id.settings: 
         fragment = new ForthFragment(); 
         break; 
       } 
       FragmentTransaction transaction = getSupportFragmentManager().beginTransaction(); 
       transaction.replace(R.id.frame_layout, fragment); 
       transaction.commit(); 
       setMenuIconsInMiddle(bottomNavigationView); 
       return true; 
      } 

     }); 
     bottomNavigationView.setSelectedItemId(R.id.profile); 
    } 

    /** 
    * This method is used to set margins for all the icons in the menu that is used in the 
    * bottom navigation view. 
    * @param navigationView an instance of the Bottom navigation view that holds the menu with 
    *      the icons. 
    */ 
    public void setMenuIconsInMiddle(BottomNavigationView navigationView){ 
     BottomNavigationMenuView menuView = (BottomNavigationMenuView)navigationView.getChildAt(0);  

     for(int index = 0; index <menuView.getChildCount(); index++){   
      final View iconView = menuView.getChildAt(index).findViewById(android.support.design.R.id.icon);     
      final ViewGroup.MarginLayoutParams layoutParams = (ViewGroup.MarginLayoutParams)iconView.getLayoutParams();  
      layoutParams.setMargins(0,50,0,0);  
      navigationView.requestLayout(); 
     } 
    } 

activity_main.xml中

<?xml version="1.0" encoding="utf-8"?> 
<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="com.example.hermes.profilescreen.MainActivity"> 

    <include layout="@layout/custom_toolbar"/> 
    <include layout="@layout/bottom_navigation"/> 
</RelativeLayout> 

bottom_nav_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/profile" 
     android:enabled="true" 
     android:icon="@drawable/ic_people_outline_black_24dp" 
     app:showAsAction="ifRoom" 
     android:title="" 
     /> 
    <item 
     android:id="@+id/friends" 
     android:enabled="true" 
     android:icon="@drawable/ic_person_black_24dp" 
     app:showAsAction="ifRoom" 
     android:title="" 
     /> 
    <item 
     android:id="@+id/circle" 
     android:enabled="true" 
     android:icon="@drawable/ic_panorama_fish_eye_black_24dp" 
     app:showAsAction="ifRoom" 
     android:title="" 
     /> 
    <item 
     android:id="@+id/settings" 
     android:enabled="true" 
     android:icon="@drawable/setting_white" 
     app:showAsAction="ifRoom" 
     android:title="" 
     /> 

</menu> 

bottom_navigation.xml

<?xml version="1.0" encoding="utf-8"?> 
<RelativeLayout 
    xmlns:app="http://schemas.android.com/apk/res-auto" 
    xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    > 

    <FrameLayout 
     android:layout_width="match_parent" 
     android:layout_height="match_parent" 
     android:id="@+id/frame_layout" 
     android:layout_above="@+id/bottom_navigation" 
     > 
    </FrameLayout> 
    <android.support.design.widget.BottomNavigationView 
     android:id="@+id/bottom_navigation" 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" 
     android:layout_alignParentBottom="true" 
     android:background="@color/light_black" 
     app:itemBackground="@drawable/set_backgorund" 
     app:itemIconTint="@color/item_state" 
     app:menu="@menu/bottom_nav_main" 
     /> 
</RelativeLayout> 

Answer 1

在線程上調用setMenuIconsInMiddle。試試這個： -

bottomNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() { 
     @Override 
     public boolean onNavigationItemSelected(@NonNull MenuItem item) { 

      //your code here 
      ... 
      ... 
      ... 
      //Looper.getMainLooper() runs on main thread 
      new Handler(Looper.getMainLooper()).post(new Runnable(){ 
       @Override 
       public void run() { 
        setMenuIconsInMiddle(bottomNavigationView); 
       } 
      }); 
      return true; 
     } 
    }); 

，這是爲我工作...