How to get all possible values of enum custom attribute?

Question

Assuming I have a custom attribute my_custom_enum for my views:

<attr name="my_custom_enum" format="enum">
    <enum name="first_value" value="751"/>
    <enum name="second_value" value="2222"/>
    <enum name="third_value" value="1241"/>
    <enum name="fourth_value" value="4"/>
</attr>

<declare-styleable name="CustomViewOne">
    <attr name="my_custom_enum"/>
</declare-styleable>

<declare-styleable name="CustomViewTwo">
    <attr name="my_custom_enum"/>
</declare-styleable>

is there a way to obtain all the possible values of this enum in code?

In other words:

I would like to have a way to obtain values 751, 2222, 1241 and 4. names of those values would be nice too, but are not mandatory.

what do you need it for? btw see how std enums are handled in the framework (typeface, visibility, scaleType etc) — pskink, Jan 19 '17 at 12:02
@pskink I need it for a unit test. The value of this kind of enum is passed to a different module that sets up the view. I wanted to write a test for this other module, so that I can be sure that all the possible values are taken care of. — Bartek Lipinski, Jan 19 '17 at 12:07
so you have corresponding `enum` in java rigth? then call `values()` static method on it to get all the values — pskink, Jan 19 '17 at 12:16
I would then skip the exact link I wanna test. I want to know if there is a corresponding value for every single value from `attr` inside my `enum` in java. — Bartek Lipinski, Jan 19 '17 at 12:26
+ if the specific value from `attr` is used to perform the right actions. — Bartek Lipinski, Jan 19 '17 at 12:28
ok, i see it now, maybe [this](http://stackoverflow.com/questions/18382559/how-to-get-an-enum-which-is-created-in-attrs-xml-in-code) will help — pskink, Jan 19 '17 at 13:19
I know the thread. Unfortunately there wasn't anything that would help me. Still, thanks for help. — Bartek Lipinski, Jan 19 '17 at 14:13
even if you were able to get all the info you want it would be pointless as attribute names are [almost] always different then corresponding enum names: will you have `enum XXX { first_value(751), second_value(2222) [...] }`? i dont think so — pskink, Jan 19 '17 at 14:24
That's why getting only values, and testing if there is a mapping for every single value would be enough for me. That's why `name` is not really needed. — Bartek Lipinski, Jan 19 '17 at 14:53
so `enum XX {FIRST(2222), SECOND(751), /* the rest of enums go here */ [...]}` would be ok? notice that "by mistake" i set FIRST=2222 and not 751 as in xml and SECOND=751 and not 2222 as in xml, you have four values in emum and xml but two of them are switched — pskink, Jan 19 '17 at 15:02
Maybe let me tell it a bit differently: mostly I want to test if there are all values covered. If there is anything returned for any value. That's my primary goal. Testing the proper mapping is secondary. If I could get that as well, it would be awesome, but if I have to choose one or another, the first test would be enough. — Bartek Lipinski, Jan 19 '17 at 15:14
So you have to write your own xml parser as the xml enum name/value is not saved anywhere in the final apk, only ints are used when passing `AttributeSet` values — pskink, Jan 19 '17 at 15:21
@pskink, yea alright I made that work. Why don't you post that as an answer so I can give you dem sweet reputation points :). — Bartek Lipinski, Jan 19 '17 at 19:35
its you who actually implemented this, so feel free and write how you did it in the answer — pskink, Jan 19 '17 at 19:42
sometimes great ideas are priceless, but really, this is not that one... go for it and writ the answer down... — pskink, Jan 19 '17 at 20:35

score 1 · Accepted Answer · edited May 23 '17 at 12:33

The solution I ended up with is the one suggested by pskink in the comment: parsing the attrs.xml and extracting values myself.

There are two reasons that made it perfectly reasonable to do it this way:

I need this for a Unit Test (to know a bit more about that, read my conversation with pskink in comments under the question).
Pairs name/value are not stored anywhere. Only ints are used when using AttributeSet .

The code I ended up with is this:

public final class AttrsUtils {

    private static final String TAG_ATTR = "attr";
    private static final String TAG_ENUM = "enum";
    private static final String ATTRIBUTE_NAME = "name";
    private static final String ATTRIBUTE_FORMAT = "format";
    private static final String ATTRIBUTE_VALUE = "value";

    @CheckResult
    @NonNull
    public static Map<String, Integer> getEnumAttributeValues(String attrName)
            throws ParserConfigurationException, IOException, SAXException {
        final File attrsFile = new File("../app/src/main/res/values/attrs.xml");
        DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
        DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
        Document doc = dBuilder.parse(attrsFile);
        doc.getDocumentElement().normalize();

        Map<String, Integer> fontAttributes = new ArrayMap<>();

        NodeList nList = doc.getElementsByTagName(TAG_ATTR);
        for (int temp = 0; temp < nList.getLength(); temp++) {
            Node attrNode = nList.item(temp);
            if (attrNode.getNodeType() == Node.ELEMENT_NODE) {
                Element attrElement = (Element) attrNode;
                final String name = attrElement.getAttribute(ATTRIBUTE_NAME);
                if (!attrElement.hasAttribute(ATTRIBUTE_FORMAT) || !name.equals(attrName)) {
                    continue;
                }

                final NodeList enumNodeList = attrElement.getElementsByTagName(TAG_ENUM);
                for (int i = 0, size = enumNodeList.getLength(); i < size; ++i) {
                    final Node enumNode = enumNodeList.item(i);
                    if (enumNode.getNodeType() == Node.ELEMENT_NODE) {
                        Element enumElement = (Element) enumNode;
                        fontAttributes.put(
                                enumElement.getAttribute(ATTRIBUTE_NAME),
                                Integer.parseInt(enumElement.getAttribute(ATTRIBUTE_VALUE)));
                    }
                }
                break; // we already found the right attr, we can break the loop
            }
        }
        return fontAttributes;
    }

    // Suppress default constructor for noninstantiability
    private AttrsUtils() {
        throw new AssertionError();
    }
}

This method returns a Map of name-value pairs that represent an attribute that has attrName.

For the example I wrote in the question, you would use this method like this:

Map<String, Integer> enumAttr = AttrsUtils.getEnumAttributeValues("my_custom_enum");

How to get all possible values of enum custom attribute?

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