Android Open Source - EffectiveAndroidUI Chapter View Model

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The source code is released under:

Apache License

Java Source Code

/*
 * Copyright (C) 2014 Pedro Vicente Gmez Snchez.
 */*from   w  ww  .  java 2s .  c o  m*/
 * 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.github.pedrovgs.effectiveandroidui.ui.viewmodel;

import com.github.pedrovgs.effectiveandroidui.domain.tvshow.Chapter;
import com.github.pedrovgs.effectiveandroidui.util.RandomUtils;
import com.github.pedrovgs.effectiveandroidui.util.TimeMachine;

/**
 * ViewModel crated to represent a Chapter from the presentation point of view.
 *
 * This class could be a interface implementation if the ChapterViewModel has more than one
 * implementation.
 *
 * This view model contains code to show how to implement a system update inside a ListView without
 * use a notifyDataSetChanged.
 *
 * @author Pedro Vicente Gmez Snchez
 */
public class ChapterViewModel {

  private static final int MAX_RATE_VALUE = 10;
  private static final int TWO_SECONDS = 2000;

  private final Chapter chapter;

  private Listener listener = new NullListener();

  /**
   * Runnable implementation used to simulate a system update related with the tv show rate.
   */
  private Runnable updateRateRunnable = new Runnable() {
    @Override public void run() {
      int randomRate = RandomUtils.getRandomValueBelow(MAX_RATE_VALUE);
      listener.onRateChanged(randomRate);
    }
  };

  public ChapterViewModel(Chapter chapter) {
    this.chapter = chapter;
  }

  public String getTitle() {
    return chapter.getTitle();
  }

  public String getPublishDate() {
    return chapter.getPublishDate();
  }

  /**
   * In addition to register the listener this method is going to trigger a view model update two
   * seconds in the future. This has been implemented to show how to use view model binding
   * manually
   * implemented to update each row without the full list view.
   */
  public void registerListener(final Listener listener) {
    this.listener = listener;
    TimeMachine.sendMessageToTheFuture(updateRateRunnable, TWO_SECONDS);
  }

  /**
   * Set NullListener (NullObject pattern implementation) and cancel the update sent to the future
   * when the listener was registered.
   */
  public void unregisterListener() {
    this.listener = new NullListener();
    TimeMachine.cancelMessage(updateRateRunnable);
  }

  public interface Listener {

    void onRateChanged(final int rate);
  }

  /**
   * NullObject pattern implementation to avoid listener field null checks inside this view model.
   */
  private class NullListener implements Listener {
    @Override public void onRateChanged(int rate) {
      //Empty
    }
  }
}

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