Custom font handling for Android, which caches the typefaces. Place the fonts in /assets/fonts/.

customfont_attrs.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="CustomFont">
        <attr name="font" format="string"/>
    </declare-styleable>
</resources>

CustomFontManager.java

import android.content.res.AssetManager;
import android.graphics.Typeface;

import java.util.HashMap;
import java.util.Map;

public class CustomFontManager {

    private static Map<String, Typeface> typefaces = new HashMap<String, Typeface>();

    private CustomFontManager() {
        // No instances
    }

    public static Typeface getTypeface(AssetManager assetManager, String name) {
        if(typefaces.containsKey(name))
            return typefaces.get(name);
        else
            return loadTypeface(assetManager, name);
    }

    private static synchronized Typeface loadTypeface(AssetManager assetManager, String name) {
        if(typefaces.containsKey(name))
            return typefaces.get(name);

        Typeface typeface = null;
        try {
            typeface = Typeface.createFromAsset(assetManager, name);
        } catch(RuntimeException e) {
            throw new IllegalArgumentException("Unable to load typeface. Did you remember to add it to assets/fonts?", e);
        }

        typefaces.put(name, typeface);
        return typeface;
    }

}

CustomFontTextView.java

import android.content.Context;
import android.content.res.TypedArray;
import android.util.AttributeSet;
import android.widget.TextView;

public class CustomFontTextView extends TextView {

    public CustomFontTextView(Context context) {
        super(context);
        init(context, null, 0);
    }

    public CustomFontTextView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init(context, attrs, 0);
    }

    public CustomFontTextView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        init(context, attrs, defStyle);
    }

    private void init(Context context, AttributeSet attrs, int defStyle) {
        CustomFontUtils.parseAttributes(this, context, attrs, defStyle);
    }
}

CustomFontUtils.java

import android.content.Context;
import android.content.res.TypedArray;
import android.util.AttributeSet;
import android.widget.TextView;

public class CustomFontUtils {

    private CustomFontUtils() {
        // No instances
    }

    public static void parseAttributes(TextView textView, Context context, AttributeSet attrs, int defStyle) {
        if(textView.isInEditMode())
            return; // Typeface loading isn't implemented in the IDE

        TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.CustomFont);
        try {
            String font = a.getString(R.styleable.CustomFont_font);
            if(font != null)
                textView.setTypeface(CustomFontManager.getTypeface(context.getAssets(), "fonts/" + font));
        } finally {
            a.recycle();
        }
    }

}

example_usage.xml

<com.example.CustomFontTextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Hello, World!"
    app:font="RobotoSlab-Regular.ttf"/>