I tried playing with BottomNavigationView a little ①

android.support.design.widget.BottomNavigationView is one of the official libraries.
Bottom navigation

■ Change the color of the icon and text (when selected or not selected)

1. Create a color directory in res

2. Create buttom_navigation.xml in the color directory and write the following contents

res/color/buttom_navigation.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:state_checked="true" android:color="#FFF" />
    <item android:state_pressed="true" android:color="#FFF" />
    <item android:color="#969696" />
</selector>

3. Specify for buttom navigation view

res/layout/main.xml

...
    <android.support.design.widget.BottomNavigationView
        android:id="@+id/navigation"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom"
        android:background="?android:attr/windowBackground"
        app:itemBackground="@color/themecolor"
        app:itemIconTint="@color/buttom_navigation"
        app:itemTextColor="@color/buttom_navigation"
        app:menu="@menu/navigation" />
...

reference: Customization of BottomNavigationView

■ Continue to display characters on unselected tabs

main.java

...

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

        mTextMessage = (TextView) findViewById(R.id.message);
        BottomNavigationView navigation = (BottomNavigationView) findViewById(R.id.navigation);
        navigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);
        
        // no-hide menu-text
        BottomNavigationMenuView menuView = (BottomNavigationMenuView) navigation.getChildAt(0);
        for (int i = 0; i < menuView.getChildCount(); i++) {
            BottomNavigationItemView itemView = (BottomNavigationItemView) menuView.getChildAt(i);
            itemView.setShiftingMode(false);
            itemView.setChecked(false); //Called to reflect the state of View
        }
    }

■ Fix the width and margin of all tabs

In the default state, if there are four tabs (items), the width of the selected tab will be greatly expanded and the others will be narrowed. I want to fix all four widths.

reference: Android android.support.design.widget.BottomNavigationView with 4 items not equally width [duplicate]

BottomNavigationViewHelper.java

public class BottomNavigationViewHelper {
    public static void disableShiftMode(BottomNavigationView view) {
        BottomNavigationMenuView menuView = (BottomNavigationMenuView) view.getChildAt(0);
        try {
            Field shiftingMode = menuView.getClass().getDeclaredField("mShiftingMode");
            shiftingMode.setAccessible(true);
            shiftingMode.setBoolean(menuView, false);
            shiftingMode.setAccessible(false);
            for (int i = 0; i < menuView.getChildCount(); i++) {
                BottomNavigationItemView item = (BottomNavigationItemView) menuView.getChildAt(i);
                //noinspection RestrictedApi
                item.setShiftingMode(false);
                // set once again checked value, so view will be updated
                //noinspection RestrictedApi
                item.setChecked(item.getItemData().isChecked());
            }
        } catch (NoSuchFieldException e) {
            Log.e("BNVHelper", "Unable to get shift mode field", e);
        } catch (IllegalAccessException e) {
            Log.e("BNVHelper", "Unable to change value of shift mode", e);
        }
    }
}

main.java

...
        mTextMessage = (TextView) findViewById(R.id.message);
        BottomNavigationView navigation = (BottomNavigationView) findViewById(R.id.navigation);
        BottomNavigationViewHelper.disableShiftMode(navigation);
        navigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);
...