GWT - Add and remove nodes in celltree

[Marco Mustermann]

Here I have an complete and very easy example to dynamically add/remove nodes to an celltree.
My example is not working very well. It seems there is an refresh problem.
Only closing/expanding the nodes will show the correct result. I also did not found any answer in this forum which fits to this problem.
Maybe somebody can try my example and tell me where the problem is. Any other hint is also very appreciated.

Greetings, Marco

import java.util.ArrayList;
import com.google.gwt.cell.client.AbstractCell;
import com.google.gwt.core.client.EntryPoint;
import com.google.gwt.event.dom.client.ClickEvent;
import com.google.gwt.event.dom.client.ClickHandler;
import com.google.gwt.safehtml.shared.SafeHtmlBuilder;
import com.google.gwt.user.cellview.client.CellTree;
import com.google.gwt.user.client.ui.AbsolutePanel;
import com.google.gwt.user.client.ui.Button;
import com.google.gwt.user.client.ui.RootPanel;
import com.google.gwt.view.client.ListDataProvider;
import com.google.gwt.view.client.SingleSelectionModel;
import com.google.gwt.view.client.TreeViewModel;

public class MyCelltreeTest implements EntryPoint {
  private AbsolutePanel absolutePanel;
  private CellTree cellTree;
  private Button btnAdd;
  private Button btnRemove;
  private MyTreeModel myTreeModel;
  private SingleSelectionModel<MyNode> selectionModelCellTree = null;

  @Override
  public void onModuleLoad() {
    RootPanel rootPanel = RootPanel.get();
    rootPanel.add(getAbsolutePanel(), 0, 0);
  }

  private AbsolutePanel getAbsolutePanel() {
    if (absolutePanel == null) {
      absolutePanel = new AbsolutePanel();
      absolutePanel.setSize("612px", "482px");
      absolutePanel.add(getCellTree(), 0, 0);
      absolutePanel.add(getBtnAdd(), 265, 428);
      absolutePanel.add(getBtnRemove(), 336, 428);
    }
    return absolutePanel;
  }

  private CellTree getCellTree() {
    if (cellTree == null) {
      myTreeModel = new MyTreeModel();
      cellTree = new CellTree(myTreeModel, null);
      cellTree.setSize("285px", "401px");
    }
    return cellTree;
  }

  private Button getBtnAdd() {
    if (btnAdd == null) {
      btnAdd = new Button("Add");
      btnAdd.addClickHandler(new ClickHandler() {
        @Override
        public void onClick(ClickEvent event) {

          MyNode node =   selectionModelCellTree.getSelectedObject();
          if(node != null)
            myTreeModel.addNew(node, "Bla");
        }
      });
    }
    return btnAdd;
  }

  private Button getBtnRemove() {
    if (btnRemove == null) {
      btnRemove = new Button("Remove");
      btnRemove.addClickHandler(new ClickHandler() {
        @Override
        public void onClick(ClickEvent event) {
          MyNode node = selectionModelCellTree.getSelectedObject();
          if(node != null)
            myTreeModel.remove(node);
        }
      });
    }
    return btnRemove;
  }

  public class MyNode {
    private String name;
    private ArrayList<MyNode> childs; //nodes childrens
    private MyNode parent; //track internal parent
    private MyCell cell; //for refresh - reference to visual component

    public MyNode(String name) {
      super();
      parent = null;
      this.name = name;
      childs = new ArrayList<MyNode>();
    }

    public void addSubMenu(MyNode m) {
      m.parent = this;
      childs.add(m);
    }

    public void removeMenu(MyNode m) {

      m.getParent().childs.remove(m);
    }

    public boolean hasChildrens() {
      return childs.size()>0;
    }

    public ArrayList<MyNode> getList() {
      return childs;
    }

    public MyNode getParent() {
      return parent;
    }

    public void setCell(MyCell cell) {
      this.cell = cell;
    }

    public void refresh() {
      if(parent!=null) {
        parent.refresh();
      }
      if (cell!=null) {
        cell.refresh(); //refresh tree
      }
    }

    public String getName() {
      return name;
    }

    public void setName(String name) {
      this.name = name;
    }
  }

  public class MyTreeModel implements TreeViewModel {
    private MyNode officialRoot; //default not dynamic
    private MyNode studentRoot; //default not dynamic
    private MyNode testRoot; //default not dynamic
    private MyNode root;

    public MyNode getRoot() { // to set CellTree root
      return root;
    }

    public MyTreeModel() {
      selectionModelCellTree = new SingleSelectionModel<MyNode>();
      root = new MyNode("root");
      // Default items
      officialRoot = new MyNode("Cat"); //some basic static data
      studentRoot = new MyNode("Dog");
      testRoot = new MyNode("Fish");
      root.addSubMenu(officialRoot);
      root.addSubMenu(studentRoot);
      root.addSubMenu(testRoot);
    }

    //example of add add logic
    public void addNew(MyNode myparent, String name) {
      myparent.addSubMenu(new MyNode(name));
      myparent.refresh(); //HERE refresh tree
    }
    public void remove(MyNode objToRemove) {

      objToRemove.removeMenu(objToRemove);
      objToRemove.refresh();
    }

    @Override
    public <T> NodeInfo<?> getNodeInfo(T value) {
      ListDataProvider<MyNode> dataProvider;
      MyNode myValue = null;
      if (value == null) { // root is not set
        dataProvider = new ListDataProvider<MyNode>(root.getList());
      } else {
        myValue = (MyNode) value;
        dataProvider = new ListDataProvider<MyNode>(myValue.getList());
      }
      MyCell cell = new MyCell(dataProvider); //HERE Add reference
      if (myValue != null)
        myValue.setCell(cell);
      return new DefaultNodeInfo<MyNode>(dataProvider, cell, selectionModelCellTree, null);
    }

    @Override
    public boolean isLeaf(Object value) {
      if (value instanceof MyNode) {
        MyNode t = (MyNode) value;
        if (!t.hasChildrens())
          return true;
        return false;
      }
      return false;
    }
  }

  public class MyCell extends AbstractCell<MyNode> {
    ListDataProvider<MyNode> dataProvider; //for refresh

    public MyCell(ListDataProvider<MyNode> dataProvider) {
      super();
      this.dataProvider = dataProvider;
    }
    public void refresh() {
      dataProvider.refresh();
    }

    @Override
    public void render(Context context, MyNode value, SafeHtmlBuilder sb) {
      if (value == null) {
        return;
      }
      sb.appendEscaped(value.getName());
    }
  }
}