GWT：如何以编程方式重新加载CellBrowser？ [英] GWT: How to programmatically reload CellBrowser?
问题描述
我使用的是GWT 2.1的 CellBrowser 与自定义 TreeViewModel 。 TreeViewModel反过来使用 AsyncDataProvider 来动态获取数据。这一切都很精彩 - 当用户点击一个节点时，我的AsyncDataProvider通过RPC获取结果，CellBrowser忠实地显示它们。
我觉得无法解决这个问题，但我怎样才能以编程方式告诉CellBrowser重新加载（并显示）数据？我猜我需要以某种方式获取我的根节点的AsyncDataProvider句柄，然后调用updateRowData（）& updateRowCount（），但我没有看到明显的方式来查询根DataProvider的浏览器（或其模型）。
我想我可以添加代码我的AsyncDataProvider构造函数寻找一个空参数，通过这种方式意识到嘿，我是根，并在某处存储引用，但这似乎是骇人听闻。当然，还有更好的方法可以做到这一点。
在这里倾销这么多代码的道歉，但我不知道如何简化它，并且仍然提供足够的
$ b
我的AsyncDataProvider：
private static class CategoryDataProvider extends AsyncDataProvider< Category>
{
private Category selectedCategory;
private CategoryDataProvider（Category selectedCategory）
{
this.selectedCategory = selectedCategory;
$ b @Override
protected void onRangeChanged（HasData< Category> display）
{
new AsyncCall< List< Category>>（）
{
@Override
protected void callService（AsyncCallback< List< Category>> cb）
{
//默认为root
String categoryId = -1\" ;
if（selectedCategory！= null）
{
categoryId = selectedCategory.getCategoryId（）;
}
//当一个类别被点击时，获取它的子类别
service.getCategoriesForParent（categoryId，cb）;
$ b @Override
public void onSuccess（List< Category> result）
{
//更新显示
updateRowCount（result .size（），true）;
updateRowData（0，result）;
}
} .go（）;
$ b 我的模特：
private static class CategoryTreeModel实现TreeViewModel
{
private SingleSelectionModel< Category> selectionModel设置;
public CategoryTreeModel（SingleSelectionModel< Category> selectionModel）
{
this.selectionModel = selectionModel;
}
/ **
* @返回提供指定类别的子元素的NodeInfo
* /
public< T>的nodeinfo<？> getNodeInfo（T值）
{
CategoryDataProvider dataProvider = new CategoryDataProvider（（Category）value）;
//返回一个将数据与单元格配对的节点信息。
返回新的TreeViewModel.DefaultNodeInfo< Category>（dataProvider，new CategoryCell（），selectionModel，null）;
$ b $ ** b $ b * @return如果指定的类别表示叶节点，则返回true
* /
public boolean isLeaf（Object value）
{
返回值！= null&& （（Category）value）.isLeafCategory（）;
$ / code $ / pre
最后，这是我的方式使用它们：
CategoryTreeModel model = new CategoryTreeModel（selectionModel）;
CellBrowser cellBrowser = new CellBrowser（model，null）;
解决方案看起来很多人都有这个< href =http://code.google.com/p/google-web-toolkit/issues/detail?id=5533 =nofollow>同样的问题。首先，创建一个接口，通过包装AsyncDataProvider的受保护的onRangeChanged方法来增加刷新数据提供者的能力。下面是我如何处理刷新AsyncDataProvider中的数据的方法。例如...
HasRefresh.java
pre $ public interface HasRefresh<< / p> ; HasData< T>> {
/ **
*当显示器想要刷新时调用
*
* @param显示刷新
* /
void refresh（HasData< T> display）;
}
然后，需要刷新的CellTable可以调用它通过一个Activity或者你的控制器逻辑被设置。
/ **
*自定义{@link AsyncDataProvider}。
* /
public class MyAsyncDataProvider extends
AsyncDataProvider< Entity>实现HasRefresh< Entity> {
public void refresh（实体显示）{
onRangeChanged（显示）;
}
/ **
* {@link #onRangeChanged（HasData）}在表请求
*新数据范围时被调用。您可以使用
* {@link #updateRowData（int，List）}将数据推送回显示器。
* /
@Override
protected void onRangeChanged（
HasData< Entity> display）{
currentRange = display.getVisibleRange（）;
final int start = currentRange.getStart（）;
dataServiceQuery = context.getEntities（）;
$ b $ dataServiceQuery
.execute（new DataServiceQueryHandler< Entity>（）{
$ b $ @Override
public void onQueryResponse（
DataServiceQueryResponse< Entity>响应）{
updateRowCount（response.getCount（），true）;
updateRowData（start，response.getEntities（））;
}
}）;
} // end onRangeChanged（）
} //结束MyAsyncDataProvider类
I'm using GWT 2.1's CellBrowser with a custom TreeViewModel. The TreeViewModel in turn uses an AsyncDataProvider to fetch data dynamically. This all works beautifully- when the user clicks on a node my AsyncDataProvider fetches the results via RPC, and the CellBrowser dutifully displays them.
I feel silly for not being able to figure this out, but how can I programmatically tell the CellBrowser to reload (and display) the data? I'm guessing that I need to somehow get a handle to the AsyncDataProvider for my root node and then call updateRowData() & updateRowCount() on it, but I don't see an obvious way to query the browser (or its model) for the root DataProvider.
I guess I could add code to my AsyncDataProvider constructor that looks for a null argument, and by that means recognize "hey, I'm the root" and store a reference somewhere, but that seems hackish. Surely there's a better way to do this.
Apologies for dumping so much code here, but I don't know how to boil this down to anything simpler and still provide enough context.
My AsyncDataProvider:
private static class CategoryDataProvider extends AsyncDataProvider<Category>
{
private Category selectedCategory;
private CategoryDataProvider(Category selectedCategory)
{
this.selectedCategory = selectedCategory;
}
@Override
protected void onRangeChanged(HasData<Category> display)
{
new AsyncCall<List<Category>>()
{
@Override
protected void callService(AsyncCallback<List<Category>> cb)
{
// default to root
String categoryId = "-1";
if (selectedCategory != null)
{
categoryId = selectedCategory.getCategoryId();
}
// when a category is clicked, fetch its child categories
service.getCategoriesForParent(categoryId, cb);
}
@Override
public void onSuccess(List<Category> result)
{
// update the display
updateRowCount(result.size(), true);
updateRowData(0, result);
}
}.go();
}
}
My model:
private static class CategoryTreeModel implements TreeViewModel
{
private SingleSelectionModel<Category> selectionModel;
public CategoryTreeModel(SingleSelectionModel<Category> selectionModel)
{
this.selectionModel = selectionModel;
}
/**
* @return the NodeInfo that provides the children of the specified category
*/
public <T> NodeInfo<?> getNodeInfo(T value)
{
CategoryDataProvider dataProvider = new CategoryDataProvider((Category) value);
// Return a node info that pairs the data with a cell.
return new TreeViewModel.DefaultNodeInfo<Category>(dataProvider, new CategoryCell(), selectionModel, null);
}
/**
* @return true if the specified category represents a leaf node
*/
public boolean isLeaf(Object value)
{
return value != null && ((Category) value).isLeafCategory();
}
}
And finally, here's how I'm using them:
CategoryTreeModel model = new CategoryTreeModel(selectionModel);
CellBrowser cellBrowser = new CellBrowser(model, null);
It looks like a lot of people are having this same issue. Here's how I handled refreshing the data from an AsyncDataProvider.
First, create an interface that adds the ability to refresh data provider by wrapping the AsyncDataProvider's protected onRangeChanged method. For example...
HasRefresh.java
public interface HasRefresh<HasData<T>>{
/**
* Called when a display wants to refresh
*
* @param display the display to refresh
*/
void refresh(HasData<T> display);
}
Then the CellTable needing to be refreshed can then call into it through an Activity or however your controller logic is setup.
/**
* A custom {@link AsyncDataProvider}.
*/
public class MyAsyncDataProvider extends
AsyncDataProvider<Entity> implements HasRefresh<Entity> {
public void refresh(Entity display){
onRangeChanged(display);
}
/**
* {@link #onRangeChanged(HasData)} is called when the table requests a
* new range of data. You can push data back to the displays using
* {@link #updateRowData(int, List)}.
*/
@Override
protected void onRangeChanged(
HasData<Entity> display) {
currentRange = display.getVisibleRange();
final int start = currentRange.getStart();
dataServiceQuery = context.getEntities();
dataServiceQuery
.execute(new DataServiceQueryHandler<Entity>() {
@Override
public void onQueryResponse(
DataServiceQueryResponse<Entity> response) {
updateRowCount(response.getCount(), true);
updateRowData(start, response.getEntities());
}
});
}// end onRangeChanged()
}// end MyAsyncDataProvider class
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