leftTreeLayout.setHeight100();
leftTreeLayout.setWidth(200);
leftTreeLayout.setShowResizeBar(true);
leftTreeLayout.setMembersMargin(1);
SampleTree sampleTree = new SampleTree();
sampleTree.addLeafClickHandler(new LeafClickHandler() {
public void onLeafClick(LeafClickEvent event) {
TreeNode node = event.getLeaf();
prepareSample(node);
}