Android - how to find multiple views with common attribute

Question

I have a layout with multiple ImageViews, some of those images need to have the same onClickListener. I would like my code to be flexible and to be able to get

Answer 1

I will share my functional-style method with a filter, can be used with StreamSupport library.

@NonNull
public static  Function> subViews(
    @NonNull final Function> filter
) {
    return view -> RefStreams.concat(
        // If current view comply target condition adds it to the result (ViewGroup too)
        filter.apply(view).map(RefStreams::of).orElse(RefStreams.empty()),

        // Process children if current view is a ViewGroup
        ofNullable(view).filter(__ -> __ instanceof ViewGroup).map(__ -> (ViewGroup) __)
                .map(viewGroup -> IntStreams.range(0, viewGroup.getChildCount())
                        .mapToObj(viewGroup::getChildAt)
                        .flatMap(subViews(filter)))
                .orElse(RefStreams.empty()));
}

@NonNull
public static  Function> hasType(@NonNull final Class type) {
    return view -> Optional.ofNullable(view).filter(type::isInstance).map(type::cast);
}

@NonNull
public static Function> hasTag(@NonNull final String tag) {
    return view -> Optional.ofNullable(view).filter(v -> Objects.equals(v.getTag(), tag));
}

Usage example:

Optional.ofNullable(navigationViewWithSubViews)
            .map(subViews(hasType(NavigationView.class)))
            .orElse(RefStreams.empty())
            .forEach(__ -> __.setNavigationItemSelectedListener(this));