从XML创建的所有Drawable

/**
     * Create a drawable from inside an XML document using an optional
     * {@link Theme}. Called on a parser positioned at a tag in an XML
     * document,tries to create a Drawable from that tag. Returns {@code null}
     * if the tag is not a valid drawable.
     */
    public static Drawable createFromXmlInner(Resources r,XmlPullParser parser,AttributeSet attrs,Theme theme) throws XmlPullParserException,IOException {
        final Drawable drawable;

        final String name = parser.getName();
        switch (name) {
            case "selector":
                drawable = new StateListDrawable();
                break;
            case "animated-selector":
                drawable = new AnimatedStateListDrawable();
                break;
            case "level-list":
                drawable = new LevelListDrawable();
                break;
            case "layer-list":
                drawable = new LayerDrawable();
                break;
            case "transition":
                drawable = new TransitionDrawable();
                break;
            case "ripple":
                drawable = new RippleDrawable();
                break;
            case "color":
                drawable = new ColorDrawable();
                break;
            case "shape":
                drawable = new GradientDrawable();
                break;
            case "vector":
                drawable = new VectorDrawable();
                break;
            case "animated-vector":
                drawable = new AnimatedVectorDrawable();
                break;
            case "scale":
                drawable = new ScaleDrawable();
                break;
            case "clip":
                drawable = new ClipDrawable();
                break;
            case "rotate":
                drawable = new RotateDrawable();
                break;
            case "animated-rotate":
                drawable = new AnimatedRotateDrawable();
                break;
            case "animation-list":
                drawable = new AnimationDrawable();
                break;
            case "inset":
                drawable = new InsetDrawable();
                break;
            case "bitmap":
                drawable = new BitmapDrawable(r);
                if (r != null) {
                    ((BitmapDrawable) drawable).setTargetDensity(r.getDisplayMetrics());
                }
                break;
            case "nine-patch":
                drawable = new NinePatchDrawable();
                if (r != null) {
                    ((NinePatchDrawable) drawable).setTargetDensity(r.getDisplayMetrics());
                }
                break;
            default:
                throw new XmlPullParserException(parser.getPositionDescription() +
                        ": invalid drawable tag " + name);

        }
        drawable.inflate(r,parser,attrs,theme);
        return drawable;
    }