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Rich Internet Application Framework for GWT
There is a newer version: 2.3.1-gwt22
/*
 * Ext GWT 2.2.0 - Ext for GWT
 * Copyright(c) 2007-2010, Ext JS, LLC.
 * [email protected]
 * 
 * http://extjs.com/license
 */
package com.extjs.gxt.ui.client.data;

import java.util.ArrayList;
import java.util.List;

import com.extjs.gxt.ui.client.event.BaseEvent;
import com.google.gwt.user.client.rpc.AsyncCallback;

/**
 * Default implementation of the TreeLoader interface.
 * 
 * 
 * Events:
 * 
 * BeforeLoad : LoadEvent(loader, config)

 * Fires before a load operation. Listeners can cancel the action by
 * calling {@link BaseEvent#setCancelled(boolean)}.
 * 
 * loader : this
 * config : the load config
 * 
 * 
 * 
 * Load : LoadEvent(loader, config, result)

 * Fires after the button is selected.
 * 
 * loader : this
 * config : the load config
 * result : the load result
 * 
 * 
 * 
 * LoadException : LoadEvent(loader, config, result)

 * Fires after the button is selected.
 * 
 * loader : this
 * config : the load config
 * result : the load result
 * 
 * 
 * 
 * 
 * @param  the model data type
 */
public class BaseTreeLoader extends BaseLoader> implements
    TreeLoader {

  protected List children = new ArrayList();

  /**
   * Creates a new tree loader instance.
   * 
   * @param proxy the data reader
   */
  @SuppressWarnings({"unchecked", "rawtypes"})
  public BaseTreeLoader(DataProxy proxy) {
    super(proxy);
  }

  /**
   * Creates a new tree loader instance.
   * 
   * @param reader the data reader
   */
  @SuppressWarnings({"unchecked", "rawtypes"})
  public BaseTreeLoader(DataReader reader) {
    super(reader);
  }

  /**
   * Creates a new tree loader instance.
   * 
   * @param proxy the data proxy
   * @param reader the data reader
   */
  @SuppressWarnings({"unchecked", "rawtypes"})
  public BaseTreeLoader(DataProxy proxy, DataReader reader) {
    super(proxy, reader);
  }

  public boolean loadChildren(M parent) {
    children.add(parent);
    return load(parent);
  }

  public boolean hasChildren(M parent) {
    if (parent instanceof TreeModel) {
      return !((TreeModel) parent).isLeaf();
    }
    return false;
  }

  @Override
  protected void loadData(Object config, AsyncCallback> callback) {
    try {
      List data = (List) reader.read(config, config);
      callback.onSuccess(data);
    } catch (Exception e) {
      callback.onFailure(e);
    }
  }

  @Override
  @SuppressWarnings("unchecked")
  protected void onLoadFailure(Object loadConfig, Throwable t) {
    TreeLoadEvent evt = new TreeLoadEvent(this, (M) loadConfig, t);
    if (loadConfig != null && children.contains(loadConfig)) {
      evt.parent = (M) loadConfig;
      children.remove(loadConfig);
    }
    fireEvent(LoadException, evt);
  }
  
  @Override
  @SuppressWarnings("unchecked")
  protected void onLoadSuccess(Object loadConfig, List result) {
    TreeLoadEvent evt = new TreeLoadEvent(this, (M) loadConfig, result);
    if (loadConfig != null && children.contains(loadConfig)) {
      evt.parent = (M) loadConfig;
      children.remove(loadConfig);
    }
    fireEvent(Load, evt);
  }

}