Retrieving all Drawable resources from Resources object

Question

In my Android project, I want to loop through the entire collection of Drawable resources. Normally, you can only retrieve a specific resource via its ID using something like:

InputStream is = Resources.getSystem().openRawResource(resourceId)

However, I want to get all Drawable resources where I won't know their ID's beforehand. Is there a collection I can loop through or perhaps a way to get the list of resource ID's given the resources in my project?

Or, is there a way for me in Java to extract all property values from the R.drawable static class?

Answer 1

Okay, this feels a bit hack-ish, but this is what I came up with via Reflection. (Note that resources is an instance of class android.content.res.Resources.)

final R.drawable drawableResources = new R.drawable();
final Class<R.drawable> c = R.drawable.class;
final Field[] fields = c.getDeclaredFields();

for (int i = 0, max = fields.length; i < max; i++) {
    final int resourceId;
    try {
        resourceId = fields[i].getInt(drawableResources);
    } catch (Exception e) {
        continue;
    }
    /* make use of resourceId for accessing Drawables here */
}

If anyone has a better solution that makes better use of Android calls I might not be aware of, I'd definitely like to see them!

Answer 2

I have taken Matt Huggins great answer and refactored it to make it more generic:

public static void loadDrawables(Class<?> clz){
    final Field[] fields = clz.getDeclaredFields();
    for (Field field : fields) {
        final int drawableId;
        try {
            drawableId = field.getInt(clz);
        } catch (Exception e) {
            continue;
        }
        /* make use of drawableId for accessing Drawables here */
    }   
}

Usage:

loadDrawables(R.drawable.class);