On Monday, July 30, 2012 10:02:03 PM UTC+2, Thad wrote:
>
> I have a CellTree in which I want to represent something similar to a
> directory listing (actually represented in database records):
>
> public class DirectoryObject implements Serializable {
> public String name;
> public String type; // 'file' or 'folder'
> public int group;
> ...
> }
>
> This listing comes from a server application which the user must log into.
> Naturally I can't call the RPC to populate the tree until the login takes
> place.
>
> My wish is to draw the UI and upon login (or upon pressing a 'List' or
> 'Refresh' button to return an ArrayList<DirectoryObject>. From this I
> populate the previously empty tree. Objects of type 'folder' will be the
> branch nodes and will require a new RPC call with the name as a parameter
> to find the children (null gets me the highest level).
>
> My question is how, once the empty tree is present, to trigger that call
> and start my listing. So far I've got what you see below, but I'm not sure
> if it's right and I'm stumped on the UiHandler for my list button (at the
> very bottom). I'm trying to follow the CellTree examples, but they use
> static data or don't start empty.
>
> public class DirectoryPanel extends Composite {
>
> private static DirectoryPanelUiBinder uiBinder = GWT
> .create(DirectoryPanelUiBinder.class);
>
> interface DirectoryPanelUiBinder extends
> UiBinder<Widget, DirectoryPanel> {
> }
>
> private static class MyDataProvider extends
> AsyncDataProvider<DirectoryObject> {
>
> private String folderName;
>
> public MyDataProvider(DirectoryObject directory) {
> if (directory != null)
> folderName = directory.name;
> }
>
> @Override
> protected void onRangeChanged(HasData<DirectoryObject> display) {
> final Range range = display.getVisibleRange();
>
> AsyncCallback<ArrayList<DirectoryObject>> callback =
> new AsyncCallback<ArrayList<DirectoryObject>>() {
> @Override
> public void onFailure(Throwable caught) {
> Window.alert((new GwtOptixException(caught)).getMessage());
> }
>
> @Override
> public void onSuccess(ArrayList<DirectoryObject> result) {
> int start = range.getStart();
> GWT.log("onRangeChanged, start: "+start);
> updateRowData(start, result);
> }
> };
> Cold.getRpcService().getDirectoryListing(folderName, callback);
> }
> }
>
> private static class DirectoryTreeModel implements TreeViewModel {
>
> private SingleSelectionModel<DirectoryObject> selectionModel =
> new SingleSelectionModel<DirectoryObject>();
>
> public DirectoryTreeModel() {
> selectionModel.addSelectionChangeHandler(new
> SelectionChangeEvent.Handler(){
> public void onSelectionChange(SelectionChangeEvent event){
> /* Huh?
> from
> https://groups.google.com/forum/?start&hl=en#!searchin/google-web-toolkit/CellTree$20asyncdataprovider/google-web-toolkit/jdQLj_oZTek/fuKmFMrbghsJ
> but there's no getSelectedObject() in SelectionChangeEvent
> */
> //DirectoryObject rec =
> (DirectoryObject)event.getSelectedObject();
>
It's actually selectionModel.getSelectedObject() that returns your real
DirectoryObject.
> }
> });
> }
>
> @Override
> public <T> NodeInfo<?> getNodeInfo(T arg0) {
> if (arg0 instanceof DirectoryObject) {
> Cell<DirectoryObject> cell = new AbstractCell<DirectoryObject>() {
> @Override
> public void render(Context context, DirectoryObject value,
> SafeHtmlBuilder sb) {
> if (value != null) {
> sb.appendEscaped(value.name);
> }
> }
> };
> MyDataProvider provider = new
> MyDataProvider((DirectoryObject)arg0);
> return new DefaultNodeInfo<DirectoryObject>(provider, cell,
> selectionModel, null);
> // or return new DefaultNodeInfo<DirectoryObject>(provider, cell);
> ??
>
The first line: generally you should provide a selection model for all your
nodes if you want to do something when they are selected (the actual
expansion, if not a leaf, is a provider's job).
}
> return null;
> }
>
> @Override
> public boolean isLeaf(Object arg0) {
> return arg0 != null && ((DirectoryObject)arg0).name != null &&
> ((DirectoryObject)arg0).type.equals('file');
> }
> }
>
> @UiField(provided = true)
> CellTree tree;
> @UiField
> Button list;
>
> DirectoryTreeModel treeModel;
>
> public DirectoryPanel() {
> treeModel = new DirectoryTreeModel();
> tree = new CellTree(treeModel, null);
>
> initWidget(uiBinder.createAndBindUi(this));
> }
>
> @UiHandler("list")
> void onList(ClickEvent event) {
> // What here??
> }
>
> }
>
I'd:
- create the cell tree only if the user has logged in (and show something
like an empty message);
- create a root null node (as you did) but refuse the expansion/selection
until the user has logged in (probably an async provider's job, i.e., the
inner RPC is used in an authentication mechanism and refuses requests from
unauthenticated clients);
- create a default root node that does nothing at all, backed by a no-op
(null) selection model and when the used logs in, replace it with the real
selection model (I think the only way is re-instantiate the cell tree).
I think the best way to programmatically select a node is by using the
selection model, although I don't remember if it also expand inner nodes.
Hope that helps.
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