NoDefaultSpinner.java

/**
 * Copyright (c) 2013, Redsolution LTD. All rights reserved.
 *
 * This file is part of Xabber project; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License, Version 3.
 *
 * Xabber is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License,
 * along with this program. If not, see http://www.gnu.org/licenses/.
 */
package com.xabber.android.ui.widget;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

import android.content.Context;
import android.util.AttributeSet;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.Spinner;
import android.widget.SpinnerAdapter;
import android.widget.TextView;

/**
 * A modified Spinner that doesn't automatically select the first entry in the
 * list.
 * <p/>
 * Shows the prompt if nothing is selected.
 * <p/>
 * Limitations: does not display prompt if the entry list is empty.
 * <p/>
 * http://stackoverflow.com/a/3427058
 *
 * @author emmby
 */
public class NoDefaultSpinner extends Spinner {

    public NoDefaultSpinner(Context context) {
        super(context);
    }

    public NoDefaultSpinner(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public NoDefaultSpinner(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    @Override
    public void setAdapter(SpinnerAdapter orig) {
        final SpinnerAdapter adapter = newProxy(orig);

        super.setAdapter(adapter);

        try {
            final Method m = AdapterView.class.getDeclaredMethod(
                    "setNextSelectedPositionInt", int.class);
            m.setAccessible(true);
            m.invoke(this, -1);

            final Method n = AdapterView.class.getDeclaredMethod(
                    "setSelectedPositionInt", int.class);
            n.setAccessible(true);
            n.invoke(this, -1);

        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    protected SpinnerAdapter newProxy(SpinnerAdapter obj) {
        return (SpinnerAdapter) java.lang.reflect.Proxy.newProxyInstance(obj
                        .getClass().getClassLoader(),
                new Class[]{SpinnerAdapter.class}, new SpinnerAdapterProxy(
                        obj));
    }

    /**
     * Intercepts getView() to display the prompt if position < 0
     */
    protected class SpinnerAdapterProxy implements InvocationHandler {

        protected SpinnerAdapter obj;
        protected Method getView;

        protected SpinnerAdapterProxy(SpinnerAdapter obj) {
            this.obj = obj;
            try {
                this.getView = SpinnerAdapter.class.getMethod("getView",
                        int.class, View.class, ViewGroup.class);
            } catch (Exception e) {
                throw new RuntimeException(e);
            }
        }

        @Override
        public Object invoke(Object proxy, Method m, Object[] args)
                throws Throwable {
            try {
                return m.equals(getView) && (Integer) (args[0]) < 0 ? getView(
                        (Integer) args[0], (View) args[1], (ViewGroup) args[2])
                        : m.invoke(obj, args);
            } catch (InvocationTargetException e) {
                throw e.getTargetException();
            } catch (Exception e) {
                throw new RuntimeException(e);
            }
        }

        protected View getView(int position, View convertView, ViewGroup parent)
                throws IllegalAccessException {
            if (position < 0) {
                final TextView v = (TextView) ((LayoutInflater) getContext()
                        .getSystemService(Context.LAYOUT_INFLATER_SERVICE))
                        .inflate(android.R.layout.simple_spinner_item, parent,
                                false);
                v.setText(getPrompt());
                return v;
            }

            return obj.getView(position, convertView, parent);
        }

    }
}