android - How to get an enum which is created in attrs.xml in code

Question

I created a custom View (find it here) with an declare-styleable attribute of type enum. In xml I can now choose one of the enum entries for my custom attribute. Now I want to create an method to set this value programmatically, but I can not access the enum.

attr.xml

<declare-styleable name="IconView">
    <attr name="icon" format="enum">
        <enum name="enum_name_one" value="0"/>
        ....
        <enum name="enum_name_n" value="666"/>
   </attr>
</declare-styleable>     

layout.xml

<com.xyz.views.IconView
    android:id="@+id/heart_icon"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    app:icon="enum_name_x"/>

What I need is something like: mCustomView.setIcon(R.id.enum_name_x); But I can not find the enum or I even have no idea how I can get the enum or the names of the enum.

Answer 1

There does not seem to be an automated way to get a Java enum from an attribute enum - in Java you can get the numeric value you specified - the string is for use in XML files (as you show).

You could do this in your view constructor:

TypedArray a = context.getTheme().obtainStyledAttributes(
                attrs,
                R.styleable.IconView,
                0, 0);

    // Gets you the 'value' number - 0 or 666 in your example
    if (a.hasValue(R.styleable.IconView_icon)) {
        int value = a.getInt(R.styleable.IconView_icon, 0));
    }

    a.recycle();
}

If you want the value into an enum you would need to either map the value into a Java enum yourself, e.g.:

private enum Format {
    enum_name_one(0), enum_name_n(666);
    int id;

    Format(int id) {
        this.id = id;
    }

    static Format fromId(int id) {
        for (Format f : values()) {
            if (f.id == id) return f;
        }
        throw new IllegalArgumentException();
    }
}

Then in the first code block you could use:

Format format = Format.fromId(a.getInt(R.styleable.IconView_icon, 0))); 

(though throwing an exception at this point may not be a great idea, probably better to choose a sensible default value)