How to re-render a specific node in gwt cell tree - gwt

Question

I am implementing a directory structure like Windows Explorer. I want to re-render a specific node of tree after any folder operations is done such as add folder, remove folder... etc
private ListDataProvider<Object> dataProvider= new ListDataProvider<Object>();
private Object current;//store object of currentNode;
private Map<Object, ListDataProvider<Object>> keyprovider =
new HashMap<Object,ListDataProvider<Object>>();
private CellTree tree;
// keeps a map for storing dataproviders in each hierarchy ,
public void setListToCurrentNode(List<Object> newList){
//adding this newlist to current data provider not reflecting to display
keyprovider.get(currentObject).setList(newList);
}
public void onModuleLoad(){
treeSelectionModel.addSelectionChangeHandler(new SelectionChangeEvent.Handler() {
public void onSelectionChange(SelectionChangeEvent event) {
//setting current object as selected node
current = treeSelectionModel.getSelectedObject();
}
});
}

Answer 1

Data providers force to re-render corresponding DOM. Code below demonstrates how it works.
This example generates 2-leveled tree, where you can refresh (re-generate) leaf nodes by pressing Enter key on selected root node.
I tried to keep code as simple as possible, all needed stuff contained right here.
public class TestEntryPoint implements EntryPoint {
private static final Logger LOG = Logger.getLogger(TestEntryPoint.class.getName());
class Item {
String name;
boolean leaf;
public Item(String name, boolean leaf) {
this.name = name;
this.leaf = leaf;
}
#Override
public String toString() {
return "Item {name=" + name + ", leaf=" + leaf + "}";
}
}
class ItemCell extends AbstractCell<Item> {
public ItemCell() {
super("keydown");
}
#Override
public void render(Context context, Item value, SafeHtmlBuilder sb) {
if (value != null) sb.appendEscaped(value.name);
}
#Override
protected void onEnterKeyDown(
Context context, Element parent, Item value, NativeEvent event, ValueUpdater<Item> valueUpdater) {
LOG.info("ItemCell.onEnterKeyDown: value=" + value);
if (value == null || value.leaf) return;
ListDataProvider<Item> leafDataProvider = leafDataProviders.get(value.name);
if (leafDataProvider == null) return;
// -->> Here we generate new childs of selected root node
leafDataProvider.setList(generateLeafs());
}
}
class ItemTreeViewModel implements TreeViewModel {
#Override
public <T> NodeInfo<?> getNodeInfo(T value) {
return new DefaultNodeInfo<Item>(
value == null ? rootDataProvider : leafDataProviders.get(((Item) value).name),
new ItemCell());
}
#Override
public boolean isLeaf(Object value) {
return (value instanceof Item) && ((Item) value).leaf;
}
}
private int id = 0;
private CellTree cellTree;
private ListDataProvider<Item> rootDataProvider;
private Map<String, ListDataProvider<Item>> leafDataProviders = new HashMap<String, ListDataProvider<Item>>();
private List<Item> generateLeafs() {
List<Item> leafList = new ArrayList<Item>(5);
for (int j = 0; j < 5; ++j)
leafList.add(new Item("Leaf Item " + (++id), true));
return leafList;
}
public void onModuleLoad() {
List<Item> rootList = new ArrayList<Item>(10);
for (int i = 0; i < 10; ++i) {
Item rootItem = new Item("Root Item " + (++id), false);
rootList.add(rootItem);
leafDataProviders.put(rootItem.name, new ListDataProvider<Item>(generateLeafs()));
}
rootDataProvider = new ListDataProvider<Item>(rootList);
cellTree = new CellTree(new ItemTreeViewModel(), null);
cellTree.setAnimationEnabled(true);
RootLayoutPanel.get().add(cellTree);
}
}

Answer 2

Solved by Changing Listdataprovider into AsyncDataProvider ,Implementation is below
private final class DataProvider extends AsyncDataProvider<Object> {
private Object value;
private List Objs;
DataProvider(Object value) {
this.value = value;
}
public void update(List objs) {//Call update when you wanted to refresh tree
this.objs=objs;
for (HasData<Object> disp : getDataDisplays()) {
this.onRangeChanged(disp);
break;
}
}
#Override
protected void onRangeChanged(final HasData<Object> display) {
updateRowData(0, objs);
updateRowCount(objs.size(), true);
}