Ошибка: cannot resolve getAssets()

Выдаёт ошибку при вызове метода getAssets(). Ошибка cannot resolve 'getAssets()'. Код:

private Drawable getDrawableFromAssets(String path) {
    return Drawable.createFromStream(getAssets().open(path), null);
}
Drawable pickColor() {
    Drawable color[] = new Drawable[]{
            getDrawableFromAssets("ball-standart/acqamarin.png"),
            getDrawableFromAssets("ball-standart/blue.png"),
            getDrawableFromAssets("ball-standart/green.png"),
            getDrawableFromAssets("ball-standart/grey.png"),
            getDrawableFromAssets("ball-standart/night_acqamarin.png"),
            getDrawableFromAssets("ball-standart/night_blue.png"),
            getDrawableFromAssets("ball-standart/orange.png"),
            getDrawableFromAssets("ball-standart/pink.png"),
            getDrawableFromAssets("ball-standart/red.png"),
            getDrawableFromAssets("ball-standart/tomato.png"),
            getDrawableFromAssets("ball-standart/violet.png"),
            getDrawableFromAssets("ball-standart/yellow.png")
    };
    return color[getNumeric(12)];
}