Custom TextView Java Class
Put this class in com.util package
import android.content.Context;
import android.graphics.Typeface;
import android.util.AttributeSet;
import android.widget.TextView;
public class CustomTextViewRegular extends TextView {
    public CustomTextViewRegular(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        init(attrs);
    }
    public CustomTextViewRegular(Context context, AttributeSet attrs) {
        super(context, attrs);
        init(attrs);
    }
    public CustomTextViewRegular(Context context) {
        super(context);
        init(null);
    }
    private void init(AttributeSet attrs) {
        if (attrs != null) {
//          Set type face
            Typeface myTypeface = Typeface.createFromAsset(getContext()
                    .getAssets(), "Helvetica_Neue.ttf");
            setTypeface(myTypeface);
        }
    }
}
You must have Helvetica_Neue.ttf in assets folder, you can use other font as well.
How to use in xml
<com.util.CustomTextViewRegular
    android:id="@+id/txtCustom"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@string/hello_world"
    android:textColor="#727272"
    android:textSize="20dip" />
If you want to change font than you have to just change font type in Java class only.
Done