[英]Cell: how to activate a contextMenu by keyboard?
键盘无法激活单元格contextMenu :其根本原因是contextMenuEvent被调度到了焦点节点-包含表,而不是单元格。 乔纳森(Jonathan)进行的错误评估概述了解决方法:
执行此操作的“正确”方法可能是重写TableView中的buildEventDispatchChain并包括TableViewSkin(如果它实现EventDispatcher),并将其继续转发到表行中的单元格。
尝试遵循该路径(下面是ListView的示例,仅因为要实现的外观只有一个级别,而针对TableView的外观只有两个级别)。 它的工作原理是:单元格contextMenu由键盘弹出触发器激活,但相对于表格相对于单元格定位。
问题:如何挂钩调度链,使其相对于单元位于?
可运行的代码示例:
package de.swingempire.fx.scene.control.et;
import javafx.application.Application;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.event.EventDispatchChain;
import javafx.event.EventTarget;
import javafx.scene.Node;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.Cell;
import javafx.scene.control.ContextMenu;
import javafx.scene.control.ListCell;
import javafx.scene.control.ListView;
import javafx.scene.control.MenuItem;
import javafx.scene.control.Skin;
import javafx.stage.Stage;
import com.sun.javafx.event.EventHandlerManager;
import com.sun.javafx.scene.control.skin.ListViewSkin;
/**
* Activate cell contextMenu by keyboard, quick shot on ListView
* @author Jeanette Winzenburg, Berlin
*/
public class ListViewETContextMenu extends Application {
private Parent getContent() {
ObservableList<String> data = FXCollections.observableArrayList("one", "two", "three");
// ListView<String> listView = new ListView<>();
ListViewC<String> listView = new ListViewC<>();
listView.setItems(data);
listView.setCellFactory(p -> new ListCellC<>(new ContextMenu(new MenuItem("item"))));
return listView;
}
/**
* ListViewSkin that implements EventTarget and
* hooks the focused cell into the event dispatch chain
*/
private static class ListViewCSkin<T> extends ListViewSkin<T> implements EventTarget {
private EventHandlerManager eventHandlerManager = new EventHandlerManager(this);
@Override
public EventDispatchChain buildEventDispatchChain(
EventDispatchChain tail) {
int focused = getSkinnable().getFocusModel().getFocusedIndex();
if (focused > - 1) {
Cell<?> cell = flow.getCell(focused);
tail = cell.buildEventDispatchChain(tail);
}
// returning the chain as is or prepend our
// eventhandlermanager doesn't make a difference
// return tail;
return tail.prepend(eventHandlerManager);
}
// boiler-plate constructor
public ListViewCSkin(ListView<T> listView) {
super(listView);
}
}
/**
* ListView that hooks its skin into the event dispatch chain.
*/
private static class ListViewC<T> extends ListView<T> {
@Override
public EventDispatchChain buildEventDispatchChain(
EventDispatchChain tail) {
if (getSkin() instanceof EventTarget) {
tail = ((EventTarget) getSkin()).buildEventDispatchChain(tail);
}
return super.buildEventDispatchChain(tail);
}
@Override
protected Skin<?> createDefaultSkin() {
return new ListViewCSkin<>(this);
}
}
private static class ListCellC<T> extends ListCell<T> {
public ListCellC(ContextMenu menu) {
setContextMenu(menu);
}
// boiler-plate: copy of default implementation
@Override
public void updateItem(T item, boolean empty) {
super.updateItem(item, empty);
if (empty) {
setText(null);
setGraphic(null);
} else if (item instanceof Node) {
setText(null);
Node currentNode = getGraphic();
Node newNode = (Node) item;
if (currentNode == null || ! currentNode.equals(newNode)) {
setGraphic(newNode);
}
} else {
/**
* This label is used if the item associated with this cell is to be
* represented as a String. While we will lazily instantiate it
* we never clear it, being more afraid of object churn than a minor
* "leak" (which will not become a "major" leak).
*/
setText(item == null ? "null" : item.toString());
setGraphic(null);
}
}
}
@Override
public void start(Stage primaryStage) throws Exception {
Scene scene = new Scene(getContent());
primaryStage.setScene(scene);
primaryStage.show();
}
public static void main(String[] args) {
launch(args);
}
}
挖掘一些事实:
scene.processMenuEvent(...)
创建并触发contextMenuEvent scene.processMenuEvent(...)
event.copyFor(...)
仅将它们映射到新的目标局部坐标 因此,对于任何自动魔术师的希望都没有实现,我们必须重新计算位置。 一个(暂定)执行此操作的地方是自定义EventDispatcher。 下面的原始示例(阅读:缺少所有的健全性检查,未经正式测试,可能会有不想要的副作用!),在委派给注入的EventDispatcher之前,只是用新的替换了由键盘触发的contextMenuEvent。 客户端代码(例如ListViewSkin)必须在传入EventDispatchChain之前传入targetCell。
/**
* EventDispatcher that replaces a keyboard-triggered ContextMenuEvent by a
* newly created event that has screen coordinates relativ to the target cell.
*
*/
private static class ContextMenuEventDispatcher implements EventDispatcher {
private EventDispatcher delegate;
private Cell<?> targetCell;
public ContextMenuEventDispatcher(EventDispatcher delegate) {
this.delegate = delegate;
}
/**
* Sets the target cell for the context menu.
* @param cell
*/
public void setTargetCell(Cell<?> cell) {
this.targetCell = cell;
}
/**
* Implemented to replace a keyboard-triggered contextMenuEvent before
* letting the delegate dispatch it.
*
*/
@Override
public Event dispatchEvent(Event event, EventDispatchChain tail) {
event = handleContextMenuEvent(event);
return delegate.dispatchEvent(event, tail);
}
private Event handleContextMenuEvent(Event event) {
if (!(event instanceof ContextMenuEvent) || targetCell == null) return event;
ContextMenuEvent cme = (ContextMenuEvent) event;
if (!cme.isKeyboardTrigger()) return event;
final Bounds bounds = targetCell.localToScreen(
targetCell.getBoundsInLocal());
// calculate screen coordinates of contextMenu
double x2 = bounds.getMinX() + bounds.getWidth() / 4;
double y2 = bounds.getMinY() + bounds.getHeight() / 2;
// instantiate a contextMenuEvent with the cell-related coordinates
ContextMenuEvent toCell = new ContextMenuEvent(ContextMenuEvent.CONTEXT_MENU_REQUESTED,
0, 0, x2, y2, true, null);
return toCell;
}
}
// usage (f.i. in ListViewSkin)
/**
* ListViewSkin that implements EventTarget and hooks the focused cell into
* the event dispatch chain
*/
private static class ListViewCSkin<T> extends ListViewSkin<T> implements
EventTarget {
private ContextMenuEventDispatcher contextHandler =
new ContextMenuEventDispatcher(new EventHandlerManager(this));
@Override
public EventDispatchChain buildEventDispatchChain(
EventDispatchChain tail) {
int focused = getSkinnable().getFocusModel().getFocusedIndex();
Cell cell = null;
if (focused > -1) {
cell = flow.getCell(focused);
tail = cell.buildEventDispatchChain(tail);
}
contextHandler.setTargetCell(cell);
// the handlerManager doesn't make a difference
return tail.prepend(contextHandler);
}
// boiler-plate constructor
public ListViewCSkin(ListView<T> listView) {
super(listView);
}
}
编辑
只是注意到一个小故障(?),如果单元格没有单独的contextMenu,则listView上的键盘激活的contextMenu将显示在单元格位置。 如果单元格未使用它,可能找不到在事件分派中仍遗漏明显的东西(?)的方法,以不替换该事件。
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