attrs.xml

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

FontTextView.java

public class FontTextView extends TextView {

    public FontTextView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.FontTextView);
        setFont(a.getString(R.styleable.FontTextView_fontName);
        a.recycle();
    }

    public FontTextView(Context context, AttributeSet attrs) {
        super(context, attrs);
        TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.FontTextView);
        setFont(a.getString(R.styleable.FontTextView_fontName);
        a.recycle();
    }

    public FontTextView(Context context) {
        super(context);
    }

    public void setFont(String fontName) {
        if (!isInEditMode()) {
            Typeface tf = Typeface.createFromAsset(getContext().getAssets(), fontName);
            setTypeface(tf);
        }
    }

}