problem in CheckboxItem Tree

[halloula]

Hello All,
i'am trying to migrate a code from GWT to SmartGWt.
in GWT i had an HorizontalPanel,checkboxItem,and a Tree/TreeItem.

now in SmartGWT,i tried to do in the same way as the CheckBoxTree in the showcase ( http://code.google.com/p/smartgwt/so...svn1237&r=1237 ) but also applying the same logic of my ex code,in GWT.
so i 'am using : a Tree,a treeGrid, and a HLyout, a DynamicalForm for the checkBoxItem.

first : should i use a TreeGridField ? 'cause in the exmaple of the showcase,they used a Treenode [] ,but before i used to have TreeItem,so i was wondering if TreeGridField would do the same job.
any way,i'am having a problem ,'cause i don't have any checkbox,or tree..
here is my code bellow :

	tree = new Tree();

		final CheckboxItem checkBox1 = new CheckboxItem();
	    checkBox1.setRedrawOnChange(true);
		checkBox1.setValue(true);
		DynamicForm df = new DynamicForm(); 
		df.setFields(checkBox1);
			
        HLayout hLayout = new HLayout();
		hLayout.setMargin(1);
	
	    hLayout.addChild(df); 
		
		TreeGridField field1 = new TreeGridField("employé") ;
		TreeGridField field2 = new TreeGridField("employé") ;
		TreeGridField field3 = new TreeGridField("employé") ;


	
		gridBasedOnTree.setData(tree);
		gridBasedOnTree.setWidth(500);
		gridBasedOnTree.setHeight(400);
		gridBasedOnTree.setSelectionAppearance(SelectionAppearance.CHECKBOX); 
		gridBasedOnTree.setAnimateFolders(true);
		gridBasedOnTree.setShowPartialSelection(true);  
		gridBasedOnTree.setCascadeSelection(true); 
		gridBasedOnTree.addDrawHandler(new DrawHandler() {  
			       public void onDraw(DrawEvent event) {  
			    	   gridBasedOnTree.getTree().openAll();  
			           }  
			       });  
		gridBasedOnTree.setFields(field1,field2,field3) ;
		hLayout.addChild(gridBasedOnTree);
		
		
//in my class i extend from Composite class of GWT.
		initWidget(gridBasedOnTree);