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我想製作一個GWT CellTree，帶有一個可選的彈出菜單，點擊一個TreeNode。GWT CellTree帶有一個可選的彈出式菜單，點擊一個TreeNode
所以我製作了一個CustomTreeModel。那就是：
public class CustomTreeModel implements TreeViewModel {
/**
* Save visited URL. We'll use it later to determine if tree node needs to be opened.
* We decode the query string in URL so that token has a chance of matching (e.g., convert %20 to space).
*/
private final String url = URL.decodeQueryString(Window.Location.getHref());
private final NavNode navNode;
private final TokenService<MainEventBus> tokenService;
/**
* A selection model shared across all nodes in the tree.
*/
private final SingleSelectionModel<NavNode> selectionModel = new SingleSelectionModel<NavNode>();
public CustomTreeModel(NavNode navNode, TokenService tokenService) {
this.navNode = navNode;
this.tokenService = tokenService;
}
@Override
public <T> NodeInfo<?> getNodeInfo(T value) {
DefaultNodeInfo<NavNode> result = null;
if (value == null) {
// LEVEL 0.
// We passed null as the root value. Return the immediate descendants.
result = new DefaultNodeInfo<NavNode>(getDataProvider(navNode), getCell(), selectionModel, null);
} else if (value instanceof NavNode) {
// all other levels
// We pass a node, return its immediate descendants.
// select node if URL contains params in node's target or one of node's option's target
NavNode currNode = (NavNode) value;
if (isSelected(currNode)) {
selectionModel.setSelected(currNode, true);
}
if (currNode.hasOptions()) { // add pop-up menu to this node if it has options
result = new DefaultNodeInfo<NavNode>(getDataProvider(currNode), getCell(), selectionModel, new NodeSelectionEventManager(currNode), null);
} else {
result = new DefaultNodeInfo<NavNode>(getDataProvider(currNode), getCell(), selectionModel, null);
}
}
return result;
}
@Override
public boolean isLeaf(Object value) {
boolean result = true;
if (value == null) {
if (navNode.hasChildren()) {
result = false;
}
} else if (value instanceof NavNode) {
NavNode currentNode = (NavNode) value;
if (currentNode.hasChildren()) {
result = false;
}
}
return result;
}
// Create a data provider that contains the immediate descendants.
private ListDataProvider<NavNode> getDataProvider(NavNode node) {
return new ListDataProvider<NavNode>(node.getChildren());
}
// Create a cell to display a descendant.
private Cell<NavNode> getCell() {
Cell<NavNode> cell = new AbstractCell<NavNode>() {
@Override
public void render(Context context, NavNode value, SafeHtmlBuilder sb) {
if (value != null) {
sb.appendEscaped(value.getName());
}
}
};
return cell;
}
private boolean isSelected(NavNode node) {
boolean selected = false;
if (node != null) {
if (url.contains(tokenService.getToken(node))) {
selected = true;
} else {
for (NavOption option: node.getOptions()) {
if (url.contains(tokenService.getToken(option))) {
selected = true;
break;
}
}
}
}
return selected;
}
class NavNodeSelectionHandler implements SelectionChangeEvent.Handler {
private final VerticalPanel optionsContainer;
private final DecoratedPopupPanel optionsPopup;
public NavNodeSelectionHandler() {
optionsPopup = new DecoratedPopupPanel(true);
optionsContainer = new VerticalPanel();
optionsContainer.setWidth("125px");
// TODO provide a debug id... this will most likely necessitate generation of a unique key
optionsPopup.setWidget(optionsContainer);
}
@Override
public void onSelectionChange(SelectionChangeEvent event) {
NavNode node = selectionModel.getSelectedObject();
for (NavOption option: node.getOptions()) {
optionsContainer.add(new Hyperlink(option.getName(), tokenService.getToken(option)));
}
// Reposition the popup relative to node
UIObject source = (UIObject) event.getSource();
int left = source.getAbsoluteLeft() + 25;
int top = source.getAbsoluteTop();
optionsPopup.setPopupPosition(left, top);
// Show the popup
optionsPopup.show();
}
}
class NodeSelectionEventManager implements CellPreviewEvent.Handler<NavNode> {
private final VerticalPanel optionsContainer;
private final DecoratedPopupPanel optionsPopup;
public NodeSelectionEventManager(NavNode node) {
optionsPopup = new DecoratedPopupPanel(true);
optionsContainer = new VerticalPanel();
optionsContainer.setWidth("125px");
for (NavOption option: node.getOptions()) {
optionsContainer.add(new Hyperlink(option.getName(), tokenService.getToken(option)));
}
// TODO provide a debug id... this will most likely necessitate generation of a unique key
optionsPopup.setWidget(optionsContainer);
}
@Override
public void onCellPreview(CellPreviewEvent<NavNode> event) {
// Reposition the popup relative to node
UIObject source = (UIObject) event.getDisplay();
int left = source.getAbsoluteLeft() + 25;
int top = source.getAbsoluteTop();
optionsPopup.setPopupPosition(left, top);
// Show the popup
optionsPopup.show();
}
}
}
我使用一個通用的bean（NavNode）可以幫助我確定當我有一個葉，當我有一個選項（NavOption）或選項包含一個目標用於超鏈接構建。
我希望當我點擊CellTree中的一個節點（TreeNode）時，出現一個彈出式菜單（DecoratedPopupPanel），但僅限於那些有選項的節點。
我試圖使用任何內部處理程序實現（構建一個DefaultNodeInfo）沒有成功。希望從上面的代碼示例中，您可以看到我想要做的事情。
下面是增加了一個SelectionChangeEvent.Handler到SingleSelectionModel
if (currNode.hasOptions()) { // add pop-up menu to this node if it has options
selectionModel.addSelectionChangeHandler(new NavNodeSelectionHandler());
result = new DefaultNodeInfo<NavNode>(getDataProvider(currNode), getCell(), selectionModel, null);
}
發生了什麼事是，投事件的嘗試失敗，一個ClassCastException的變體。
我想得到一個UIObject的句柄，所以我可以定位彈出窗口。我認爲我需要一個TreeNode的句柄，但看不到如何去做。
CellTree，TreeViewModel，SelectionModel和朋友是我遇到過的最鈍的API之一。
真的很感謝GWT專家的幫助！
我有一個基於GWT樹的impl滿足上述用例，但它不適用於大樹。 – 2012-01-12 23:52:54