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Setting item selected state in Android GridView

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When working with the GridView in an Android app recently, I ran into a very strange behavior around setting the selected state for a view created in my ArrayAdapter's getView() method.  I'm using selectors to handle the drawable states and everything works properly when tapping a list item to select/tapping again to unselect.  When debugging the ArrayAdapter's getView() method, I could see that the selected state was being set to the correct value when calling view.setSelected(), but the button background was not updated to the proper state.

After going on the obligatory StackOverflow & Google scavenger hunt, I eventually came across this post, which addresses how to call the setSelection() method in a single-select ListView.  It turns out that the same approach is needed when calling setSelected() on an individual view.

In short, you must do this:

private void setSelected(final View view, final boolean selected) {
    view.post(new Runnable() {
        @Override
        public void run() {
            view.setSelected(selected);
        }
    });
}

The key is posting a runnable on the UI thread to set the selected state. Otherwise, the view is marked as selected but its visual state is unchanged.

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