Equivalent of CSS class selectors for Android views?

Question

Do Android views have something equivalent to CSS class selectors? Something like R.id but usable for multiple views? I would like to hide some group of views independent of their position in the layout tree.

Answer 1

I think that you will need to iterate through all of the views in your layout, looking for the android:id you want. You can then use View setVisibility() to change the visibility. You could also use the View setTag() / getTag() instead of android:id to mark the views that you want to handle. Eg, the following code uses a general purpose method to traverse the layout:

// Get the top view in the layout.
final View root = getWindow().getDecorView().findViewById(android.R.id.content);

// Create a "view handler" that will hide a given view.
final ViewHandler setViewGone = new ViewHandler() {
    public void process(View v) {
        // Log.d("ViewHandler.process", v.getClass().toString());
        v.setVisibility(View.GONE);
    }
};

// Hide any view in the layout whose Id equals R.id.textView1.
findViewsById(root, R.id.textView1, setViewGone);


/**
 * Simple "view handler" interface that we can pass into a Java method.
 */
public interface ViewHandler {
    public void process(View v);
}

/**
 * Recursively descends the layout hierarchy starting at the specified view. The viewHandler's
 * process() method is invoked on any view that matches the specified Id.
 */
public static void findViewsById(View v, int id, ViewHandler viewHandler) {
    if (v.getId() == id) {
        viewHandler.process(v);
    }
    if (v instanceof ViewGroup) {
        final ViewGroup vg = (ViewGroup) v;
        for (int i = 0; i < vg.getChildCount(); i++) {
            findViewsById(vg.getChildAt(i), id, viewHandler);
        }
    }
}

Answer 2

You can set same tag for all such views and then you can get all the views having that tag with a simple function like this:

private static ArrayList<View> getViewsByTag(ViewGroup root, String tag){
    ArrayList<View> views = new ArrayList<View>();
    final int childCount = root.getChildCount();
    for (int i = 0; i < childCount; i++) {
        final View child = root.getChildAt(i);
        if (child instanceof ViewGroup) {
            views.addAll(getViewsByTag((ViewGroup) child, tag));
        }

        final Object tagObj = child.getTag();
        if (tagObj != null && tagObj.equals(tag)) {
            views.add(child);
        }

    }
    return views;
}

As explained in Shlomi Schwartz answer . Obviously this is not as useful as css classes are. But this might be a little useful as compared to writing code to iterate your views again and again.