Retrieving all Drawable resources from Resources o

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

Add a picture named aaaa and another named zzzz, then iterate through the following:

public static void loadDrawables() {
  for(long identifier = (R.drawable.aaaa + 1);
      identifier <= (R.drawable.zzzz - 1);
      identifier++) {
    String name = getResources().getResourceEntryName(identifier);
    //name is the file name without the extension, indentifier is the resource ID
  }
}

This worked for me.

Answer 2

Just do this:

Field[] declaredFields = (R.drawable.class).getDeclaredFields();

Answer 3

The OP wanted drawables and I needed layouts. This is what I came up with for layouts. The name.startsWith business lets me ignore system generated layouts, so you may need to tweak that a bit. This should work for any resource type by modifying the value of clz.

public static Map<String,Integer> loadLayouts(){
    final Class<?> clz = R.layout.class;
    Map<String,Integer> layouts = new HashMap<>();
    final Field[] fields = clz.getDeclaredFields();
    for (Field field : fields) {
        String name = field.getName();
        if (
                !name.startsWith("abc_")
                && !name.startsWith("design_")
                && !name.startsWith("notification_")
                && !name.startsWith("select_dialog_")
                && !name.startsWith("support_")
        ) {
            try {
                layouts.put(field.getName(), field.getInt(clz));
            } catch (Exception e) {
                continue;
            }
        }
    }
    return layouts;
}

Answer 4

If you find yourself wanting to do this you're probably misusing the resource system. Take a look at assets and AssetManager if you want to iterate over files included in your .apk.

Answer 5

i used getResources().getIdentifier to scan through sequentially named images in my resource folders. to be on a safe side, I decided to cache image ids when activity is created first time:

    private void getImagesIdentifiers() {

    int resID=0;        
    int imgnum=1;
    images = new ArrayList<Integer>();

    do {            
        resID=getResources().getIdentifier("img_"+imgnum, "drawable", "InsertappPackageNameHere");
        if (resID!=0)
            images.add(resID);
        imgnum++;
    }
    while (resID!=0);

    imageMaxNumber=images.size();
}

Answer 6

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!