src/com/android/mms/transaction/Observable.java

/*
 * Copyright (C) 2007-2008 Esmertec AG.
 * Copyright (C) 2007-2008 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.mms.transaction;

import java.util.ArrayList;
import java.util.Iterator;


/**
 * An interface to represent the state of an observable Transaction.
 */
public abstract class Observable {
    private final ArrayList<Observer> mObservers;
    private Iterator<Observer> mIterator;

    public Observable() {
        mObservers = new ArrayList<Observer>();
    }

    /**
     * This method is implemented by the observable to represent its
     * current state.
     *
     * @return A TransactionState object.
     */
    abstract public TransactionState getState();

    /**
     * Attach an observer to this object.
     *
     * @param observer The observer object to be attached to.
     */
    public void attach(Observer observer) {
        mObservers.add(observer);
    }

    /**
     * Detach an observer from this object.
     *
     * @param observer The observer object to be detached from.
     */
    public void detach(Observer observer) {
        if (mIterator != null) {
            mIterator.remove();
        } else {
            mObservers.remove(observer);
        }
    }

    /**
     * Notify all observers that a status change has occurred.
     */
    public void notifyObservers() {
        mIterator = mObservers.iterator();
        try {
            while (mIterator.hasNext()) {
                mIterator.next().update(this);
            }
        } finally {
            mIterator = null;
        }
    }
}