Adam Adam - 23 days ago 10
Android Question

Equivalent of CSS class selectors for Android views?

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

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. E.g., 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);
        }
    }
}