How to Set a Custom Font in the ActionBar Title?

int titleId = getResources().getIdentifier("action_bar_title", "id",
            "android");
    TextView yourTextView = (TextView) findViewById(titleId);
    yourTextView.setTextColor(getResources().getColor(R.color.black));
    yourTextView.setTypeface(face);

From Android Support Library v26 + Android Studio 3.0 onwards, this process has become easy as a flick!!

Follow these steps to change the font of Toolbar Title:

1. Read Downloadable Fonts & select any font from the list (my recommendation) or load a custom font to res > font as per Fonts in XML

2. In res > values > styles, paste the following (use your imagination here!)

   <style name="TitleBarTextAppearance" parent="android:TextAppearance">
       <item name="android:fontFamily">@font/your_desired_font</item>
       <item name="android:textSize">23sp</item>
       <item name="android:textStyle">bold</item>
       <item name="android:textColor">@android:color/white</item>
   </style>
   

3. Insert a new line in your Toolbar properties app:titleTextAppearance="@style/TextAppearance.TabsFont" as shown below

   <android.support.v7.widget.Toolbar
       android:id="@+id/toolbar"
       android:layout_width="match_parent"
       android:layout_height="?attr/actionBarSize"
       android:background="?attr/colorPrimary"
       app:titleTextAppearance="@style/TitleBarTextAppearance"
       app:popupTheme="@style/AppTheme.PopupOverlay"/>
   

4. Enjoy Custom Actionbar Title font styling!!

You can do this using a custom TypefaceSpan class. It's superior to the customView approach indicated above because it doesn't break when using other Action Bar elements like expanding action views.

The use of such a class would look something like this:

SpannableString s = new SpannableString("My Title");
s.setSpan(new TypefaceSpan(this, "MyTypeface.otf"), 0, s.length(),
        Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);

// Update the action bar title with the TypefaceSpan instance
ActionBar actionBar = getActionBar();
actionBar.setTitle(s);

The custom TypefaceSpan class is passed your Activity context and the name of a typeface in your assets/fonts directory. It loads the file and caches a new Typeface instance in memory. The complete implementation of TypefaceSpan is surprisingly simple:

/**
 * Style a {@link Spannable} with a custom {@link Typeface}.
 * 
 * @author Tristan Waddington
 */
public class TypefaceSpan extends MetricAffectingSpan {
      /** An <code>LruCache</code> for previously loaded typefaces. */
    private static LruCache<String, Typeface> sTypefaceCache =
            new LruCache<String, Typeface>(12);

    private Typeface mTypeface;

    /**
     * Load the {@link Typeface} and apply to a {@link Spannable}.
     */
    public TypefaceSpan(Context context, String typefaceName) {
        mTypeface = sTypefaceCache.get(typefaceName);

        if (mTypeface == null) {
            mTypeface = Typeface.createFromAsset(context.getApplicationContext()
                    .getAssets(), String.format("fonts/%s", typefaceName));

            // Cache the loaded Typeface
            sTypefaceCache.put(typefaceName, mTypeface);
        }
    }

    @Override
    public void updateMeasureState(TextPaint p) {
        p.setTypeface(mTypeface);

        // Note: This flag is required for proper typeface rendering
        p.setFlags(p.getFlags() | Paint.SUBPIXEL_TEXT_FLAG);
    }

    @Override
    public void updateDrawState(TextPaint tp) {
        tp.setTypeface(mTypeface);

        // Note: This flag is required for proper typeface rendering
        tp.setFlags(tp.getFlags() | Paint.SUBPIXEL_TEXT_FLAG);
    }
}

Simply copy the above class into your project and implement it in your activity's onCreate method as shown above.

I agree that this isn't completely supported, but here's what I did. You can use a custom view for your action bar (it will display between your icon and your action items). I'm using a custom view and I have the native title disabled. All of my activities inherit from a single activity, which has this code in onCreate:

this.getActionBar().setDisplayShowCustomEnabled(true);
this.getActionBar().setDisplayShowTitleEnabled(false);

LayoutInflater inflator = LayoutInflater.from(this);
View v = inflator.inflate(R.layout.titleview, null);

//if you need to customize anything else about the text, do it here.
//I'm using a custom TextView with a custom font in my layout xml so all I need to do is set title
((TextView)v.findViewById(R.id.title)).setText(this.getTitle());

//assign the view to the actionbar
this.getActionBar().setCustomView(v);

And my layout xml (R.layout.titleview in the code above) looks like this:

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

<com.your.package.CustomTextView
        android:id="@+id/title"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerVertical="true"
            android:layout_marginLeft="10dp"
            android:textSize="20dp"
            android:maxLines="1"
            android:ellipsize="end"
            android:text="" />
</RelativeLayout>