GWT CellTree @UIHandler SelectionChanged

Question

我正在使用GWT CellTree类，并且希望能够在选择更改时更新页面上的另一个UI元素。

我有这个：

@UiField (provided = true)
CellTree folderTree;

在页面加载中填充数据，然后需要@UIiHandler，如下所示：

@UiHandler("folderTree")
void onTreeCellChange(????? e){
    //update UI    
}

我已经尝试过这样的方法：

ValueChangeEvent<List<Folder>> //List<Folder> being the underlying class for the CellTree.
SelectionHandler<CellTree>
ClickEvent

在所有上述情况下，在表单加载时，我都会发现延迟绑定失败。我觉得我错过了一些简单的东西，但似乎找不到我的google-fu。

Answer 1

您可以向NodeInfo of TreeViewModel of CellTree添加处理程序。

下面是可以这样做的例子：

首先，让我们定义什么是文件夹：

// the simplest possible folder even without subfolders just to make example working
public class Folder {
    private String name;

    public Folder(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

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

假设您的ui.xml的一部分如下所示：

<g:HorizontalPanel>
    <cellview:CellTree ui:field="folderTree"/>
    <g:Label ui:field="folderName"/>
</g:HorizontalPanel>

比你拥有的UiBinder：

public static interface Binder extends UiBinder<HorizontalPanel, BinderOwner> {}

下面是如何定义您的FolerTreeModel所需的CellTree：

public static class FolderTreeModel implements TreeViewModel {
    private final ListDataProvider<Folder> dataProvider;
    private final CellPreviewEvent.Handler<Folder> folderSelectionHandler;

    public FolderTreeModel(List<Folder> folders, CellPreviewEvent.Handler<Folder> folderSelectionHandler) {
        this.folderSelectionHandler = folderSelectionHandler;
        dataProvider = new ListDataProvider<Folder>(folders);
    }

    @Override
    public <T> TreeViewModel.NodeInfo<?> getNodeInfo(T value) {
        return new DefaultNodeInfo<Folder>(dataProvider, new AbstractCell<Folder>() {
            // simple renderer that renders folder name
            @Override 
            public void render(Context context, Folder value, SafeHtmlBuilder sb) {
                sb.appendEscaped(value.getName());
            }
        }, 
        new SingleSelectionModel<Folder>(), // using single selection model
        folderSelectionHandler, // add handler to the node info
        null); // value updater can be null
    }

    @Override
    public boolean isLeaf(Object value) {
        return false; // I will say that every node is not leaf for simplicity 
    }
 }

你的BinderOwner课程：

public static class BinderOwner {
    @UiField(provided = true)
    CellTree folderTree;
    @UiField
    Label folderName; //your other UI element that you will change: show the name of selected folder

    public BinderOwner() {
         //List of folders to show something
         ArrayList<Folder> folders = new ArrayList<Folder>();
         folders.add(new Folder("A"));
         folders.add(new Folder("B"));
         folders.add(new Folder("C"));

         // define folder tree
         folderTree = new CellTree(new FolderTreeModel(folders, new CellPreviewEvent.Handler<Folder>() {
             // this is your handler
             @Override 
             public void onCellPreview(CellPreviewEvent<Folder> event) {
                 // set folder name to label on folder selection
                 folderName.setText(event.getValue().getName());
             }
         }), null);
    }
}