How to set a custom font to the title in toolbar android

Update 2018 (kotlin version)

fun Toolbar.changeToolbarFont(){
    for (i in 0 until childCount) {
        val view = getChildAt(i)
        if (view is TextView && view.text == title) {
            view.typeface = Typeface.createFromAsset(view.context.assets, "fonts/customFont")
            break
        }
    }
}

and use it like that toolBar.changeToolbarFont()

old-post

To use a custom title in your Toolbar all you need to do is remember is that Toolbar is just a fancy ViewGroup so you can add a custom title like so:

<android.support.v7.widget.Toolbar
    android:id="@+id/toolbar_top"
    android:layout_height="wrap_content"
    android:layout_width="match_parent"
    android:minHeight="?attr/actionBarSize"
    android:background="@color/action_bar_bkgnd"
    app:theme="@style/ToolBarTheme" >


     <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Toolbar Title"
        android:layout_gravity="center"
        android:id="@+id/toolbar_title" />


    </android.support.v7.widget.Toolbar>

This means that you can style the TextView however you would like because it's just a regular TextView. So in your activity you can access the title like so:

Toolbar toolbarTop = (Toolbar) findViewById(R.id.toolbar_top);
TextView mTitle = (TextView) toolbarTop.findViewById(R.id.toolbar_title);

And then:

Typeface khandBold = Typeface.createFromAsset(BalrogApplication.getApplication().getAssets(), "fonts/Khand-bold.ttf");

mTitle.setTypeface(khandBold);

UPDATE dynamically version

public static void changeToolbarFont(Toolbar toolbar, Activity context) {
    for (int i = 0; i < toolbar.getChildCount(); i++) {
        View view = toolbar.getChildAt(i);
        if (view instanceof TextView) {
            TextView tv = (TextView) view;
            if (tv.getText().equals(toolbar.getTitle())) {
                applyFont(tv, context);
                break;
            }
        }
    }
}

public static void applyFont(TextView tv, Activity context) {
    tv.setTypeface(Typeface.createFromAsset(context.getAssets(), "fonts/customFont"));
}

and use it like that

changeToolbarFont(findViewById(R.id.app_bar), this);