Android adapter supplies default onLongClick if parent doesn't supply interface

Question

I have several activities that could use the same array adapter. I would like to supply a default onLongClick if the activity doesn't implement it something like:

public class BookAdapter extends ArrayAdapter<Book> {
...
    private View.OnLongClickListener onLongClickListener;
    public BookAdapter(Context context, ArrayList<Book> aBooks) {
        super(context, 0, aBooks);
        Log.i(TAG, "caller:" + context.getClass().getSimpleName());
        if (context instanceof View.OnLongClickListener) {
            Log.i(TAG, "yes");
            onLongClickListener = (View.OnLongClickListener)
                     context.onLongClickListener();
        }
        else {
            onLongClickListener = new View.OnLongClickListener() {
                public boolean onLongClick(View v)
                   String title = 
                           ((TextView)(v.findViewById(R.id.tvTitle)))
                          .getText().toString();
                   Log.v(TAG, "view onLongClick pressed for title \""
                             + title + "\"");
                   return true;
                }
            };
        }
    }
    @Override
    public View getView(
        int position, View convertView, ViewGroup parent) {
        ...
        convertView.setOnLongClickListener(onLongClickListener);
        ...
    }
...
}

But I can't seem to assign the caller onClickListener to the local onLongClickListener.

How would I do this?

Answer 1

Got it. I dug through the source of View.java to see how it was implemented and the key was to wrap the call to the parent method in the default method I supply.

public class BookAdapter extends ArrayAdapter<Book> {
    ...
    // Ref. to parent if it implements the OnLongClick interface.
    private View.OnLongClickListener mOnLongClickListener;
    public BookAdapter(Context context, ArrayList<Book> aBooks) {
        super(context, 0, aBooks);
        // save a ref. to the parent if it implements the OnLongClick interface.
        if (context instanceof View.OnLongClickListener) {
            mOnLongClickListener = (View.OnLongClickListener)context;
        }
    }
    ...
    // supply a OnLongClick method.
    private View.OnLongClickListener getOnLongClickListener() {
    if (mOnLongClickListener!= null) {
        return new View.OnLongClickListener() {
            public boolean onLongClick(View v) {
                // Call the parent method if it is implemented.
                return mOnLongClickListener.onLongClick(v);
            }
        };
    }
    else {
        return new View.OnLongClickListener() {
            public boolean onLongClick(View v) {
                String title
                    = ((TextView)(v.findViewById(R.id.tvTitle)))
                        .getText().toString();
                Log.v(TAG, "view onLongClick pressed for title \""
                    + title + "\"");
                return true;
            }
        };
    }
}
    ...
    public View getView(int position, View convertView, ViewGroup parent) {
    ...
        convertView.setOnLongClickListener(getOnLongClickListener());
        ...    
    }
    ...
}

If there's a cleaner way to do this, I'd love to hear it.

Thanks Steve Smith