How to Add Icons or Menus into the PSLab Android App Toolbar

This blog demonstrates how to add different icons like help, play, pause, etc. and/or menu bar in the toolbar of an Android app along with setting their visibilities on the toolbar i.e. to display the icons only when space is available else to add them in the menu. The topic will be mainly explained by taking the example of menus and icons added to the PSLab app.

How to add a menu in a toolbar?

Following are the steps to add a menu or an icon in the toolbar widget of the Android app

  • First, add toolbar widget to the main layout file as follows
<android.support.v7.widget.Toolbar
   android:id="@+id/compass_toolbar"
   android:layout_width="match_parent"
   android:layout_height="?attr/actionBarSize"
   android:background="?attr/colorPrimary"
   app:popupTheme="@style/AppTheme.PopupOverlay"
   app:title="@string/compass" />

Here, popupTheme is the theme that activates when inflating the toolbar. Usually, it is kept similar to the default theme of the toolbar.

  • Now as the toolbar is ready, we can make the menu that needs to be inflated on the toolbar. For making a menu, make a folder named menu in the resources folder. Now, add a menu resource file in it by giving a proper name and then add the following code
<?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/compass_help_icon"
       android:icon="@drawable/compass_help_icon"
       android:title="@string/show_axis_help"
       app:showAsAction="always" />
</menu>

A detailed explanation of the above code is as follows:

  1. The <menu>…</menu> covers all the items in the menu. There can be sub-menu and also sub-sub-menu too. To make a sub-menu, use <menu>…</menu> inside the main menu.
  2. The <item> tag inside the menu defines a specific item to be included in the menu. The icon attribute of an item is used to show the icon on the toolbar. The title attribute of an item is used to show the text inside the menu if space isn’t available to show the icon on the toolbar. The showAsAction attribute is used to define the method of an item i.e. how the item should be visible to the user. Following are some of the values that showAsAction attribute can take:
    • always – It is used to show the icon of the item on the toolbar everytime
    • never – It is used to show the item as a text in the menu everytime the activity is opened
    • ifRoom – It is used to show the icon on the toolbar if there is enough space else the item is included in the menu

NOTE: Always give IDs to menu items as they are used to distinctly identify the item in the java code.

Figure 1. Example of menu and icons in toolbar in PSLab app

As shown in figure 1, the first two icons have always value in their showAsAction attribute whereas other items have never values in their showAsAction attribute.

  • Now the layout and the menu are ready to be inflated from the Java code. First, the toolbar needs to be set up from the Java code. So find the toolbar with its id and then write the following line in the code.
setSupportActionBar(mToolbar);
  • Now the toolbar is ready and so the menu can be inflated on it. So, override the following method to inflate the menu
@Override
public boolean onCreateOptionsMenu(Menu menu) {
   MenuInflater inflater = getMenuInflater();
   inflater.inflate(R.menu.activity_compass_help_menu, menu);
   return true;
}

Here, the getMenuInflater() method is used to inflate the menu on the toolbar.

  • Now override the onCreateOptionsMenu() method to do the predefined task of selecting the icon or the item from the menu.
@Override
public boolean onOptionsItemSelected(MenuItem item) {
   switch (item.getItemId()) {
       case R.id.compass_help_icon:
           // Do something
           break;
       default:
           break;
   }
   return true;
}

So, in this way a menu can be made so that the number of items delivered to the user can be increased by using the minimum space possible.

Resources

  1. https://developer.android.com/guide/topics/ui/menus – Android Developers guide on how to make a menu in Android