Events GWT CellTree，具有一个可选的弹出菜单，可在单击树节点时触发

我想制作一个GWT CellTree，它有一个可选的弹出菜单，点击TreeNode就会触发

所以我制作了一个CustomTreeModel。这是：

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();

    }

}

}

我正在使用一个通用bean NavNode来帮助我确定何时有一个叶，何时有一个选项NavOption或包含用于超链接构建的目标的选项

我想，当我点击CellTree中的节点树节点时，会出现一个弹出菜单DecoratedPopupPanel，但只针对那些具有选项的节点

我曾尝试在构建DefaultNodeInfo时使用任何一种内部处理程序实现，但都没有成功。希望通过上面的代码示例，您可以看到我正在尝试做什么

下面是一个将SelectionChangeEvent.Handler添加到SingleSelectionModel的变量

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);
        }

发生的情况是，尝试强制转换事件失败，并出现ClassCastException。 我想在UIObject上获得一个句柄，以便定位弹出窗口。我想我需要一个树状物的把手，但我不知道怎么做

CellTree、TreeViewModel、SelectionModel和friends是我见过的最迟钝的API之一

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非常感谢GWT专家的帮助

我的一位聪明的同事找到了一个解决方案

以下是我们的结论：

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);
        }
        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>(NavNodeUtil.getHeadedChildren(node.getChildren(), 1));
}

// Create a cell to display a descendant.
private Cell<NavNode> getCell() {
    return new TreeCell();
}

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 TreeCell extends AbstractCell<NavNode> {

    public TreeCell() {
        super("click", "keydown");
    }

    @Override
    public void onBrowserEvent(Context context, Element parent, NavNode currNode,
            NativeEvent event, ValueUpdater<NavNode> valueUpdater) {
        // Check that the value is not null.
        if (currNode == null) {
            return;
        }

        if (currNode.hasOptions()) { // add pop-up menu to this node if it has options
            final DecoratedPopupPanel optionsPopup = new DecoratedPopupPanel(true);
            final VerticalPanel optionsContainer = new VerticalPanel();
            optionsContainer.setWidth("125px");
            for (NavOption option: currNode.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);
            // Reposition the popup relative to node
            final int left = parent.getAbsoluteLeft() + 25;
            final int top = parent.getAbsoluteTop();

            optionsPopup.setPopupPositionAndShow(new PopupPanel.PositionCallback() {
                @Override
                public void setPosition(int offsetWidth, int offsetHeight) {
                    optionsPopup.setPopupPosition(left, top);
                }
            });
        }

        super.onBrowserEvent(context, parent, currNode, event, valueUpdater);
    }

    @Override
    public void render(Context context, NavNode value, SafeHtmlBuilder sb) {
        if (value != null) {
            sb.appendEscaped(value.getName());
        }
    }
}

}

注意TreeCell会覆盖onBrowserEvent。从这里我们可以获得节点上的句柄并定位弹出窗口。弹出窗口通过回调进行实例化。奇怪

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NavNodeUtil在计算子节点数量并为超过某个阈值的节点的子节点添加A、B、C…Z分类标题时发挥了一些神奇的作用。

我有一个基于GWT树的IML，它满足上述用例，但不适用于大型树。