How to increase icon size in android bottom navigation layout?

Question

I am using the bottom layout navigation style in android that was recently introduced by google in design library 25. In all the tutorials and questions i see, the images in their icons are a normal size, but mine are extra small, despite the fact that the image I'm saving to drawable folder is 72x72. Here is a screenshot:

The icons should be at least 2, maybe even 3 times that size. How can I do it? Here is my code in my bottom_layout.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/menu_home"
    android:title="test"
    android:icon="@drawable/tabbarglossary"
    app:showAsAction="always|withText"
    />
  <item
    android:id="@+id/menu_search"
    android:title="test2"
    android:icon="@drawable/mediationtabbar"
    app:showAsAction="always|withText"
    />

  <item
    android:id="@+id/menu_notifications"
    android:title="test3"
    android:icon="@drawable/ic_action_name"
    app:showAsAction="always|withText"
    />

</menu>

and in my activity_main.xml:

 <android.support.design.widget.BottomNavigationView
    android:id="@+id/navigation"
    android:layout_width="match_parent"
    android:layout_height="80dp"
    android:layout_alignParentBottom="true"
    android:layout_gravity="bottom"
    android:layout_marginBottom="0dp"
    android:layout_marginLeft="0dp"
    android:layout_marginRight="0dp"
    android:focusable="false"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent"
    design:menu="@menu/bottom_layout" />

Thanks

Answer 1

set app:itemIconSize property with your preferred value.

Answer 2

The icon size is hardcoded to 24dp in the item layout (see design_bottom_navigation_item.xml) This can be changed programmatically:

BottomNavigationView bottomNavigationView = (BottomNavigationView) activity.findViewById(R.id.bottom_navigation_view);
BottomNavigationMenuView menuView = (BottomNavigationMenuView) bottomNavigationView.getChildAt(0);
for (int i = 0; i < menuView.getChildCount(); i++) {
    final View iconView = menuView.getChildAt(i).findViewById(android.support.design.R.id.icon);
    final ViewGroup.LayoutParams layoutParams = iconView.getLayoutParams();
    final DisplayMetrics displayMetrics = getResources().getDisplayMetrics();
    // set your height here
    layoutParams.height = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 32, displayMetrics);
    // set your width here
    layoutParams.width = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 32, displayMetrics);
    iconView.setLayoutParams(layoutParams);
}

EDIT

For your problem that the icon covers your text:

You can override some default dimensions of the bottom navigation view. For example the height.

<dimen name="design_bottom_navigation_height" tools:override="true">56dp</dimen>

Check guidelines bottom navigation for default specs.