我正在学习javafx.scene.control.ContextMenu，现在我遇到了一个问题：
如何从EventHandler获取单击的对象？ event.source（）和event.target（）都返回MenuItem。
让我用一个例子来解释一下：我应该在函数句柄内写什么？
TextField text = new TextField();
Label label1 = new Label("hello");
Label label2 = new Label("world");
Label label3 = new Label("java");
ContextMenu menu = new ContextMenu();
MenuItem item = new MenuItem("copy to text field");
menu.getItems().add(item);
item.setOnAction(new EventHandler(){
public void handle(Event event) {
//I want to copy the text of the Label I clicked to TextField
event.consume();
}
});
label1.setContextMenu(menu);
label2.setContextMenu(menu);
label3.setContextMenu(menu);
编辑：我希望有一些简单的解决方案（一个班轮），但如果没有，那么有很多复杂的方法来做到这一点。
您可以创建自己的ContextMenu实例并向其添加操作父级以供进一步参考：
public class Main extends Application {
TextField text = new TextField();
public static void main(String[] args) {
Application.launch(args);
}
@Override
public void start(Stage primaryStage) {
Label label1 = new Label("hello");
Label label2 = new Label("world");
Label label3 = new Label("java");
label1.setContextMenu(new MyContextMenu(label1));
label2.setContextMenu(new MyContextMenu(label2));
label3.setContextMenu(new MyContextMenu(label3));
HBox root = new HBox();
root.getChildren().addAll(text, label1, label2, label3);
Scene scene = new Scene(root, 300, 100);
primaryStage.setScene(scene);
primaryStage.show();
}
private class MyContextMenu extends ContextMenu {
public MyContextMenu(Label label) {
MenuItem item = new MenuItem("copy to text field");
item.setOnAction(event -> {
// I want to copy the text of the Label I clicked to TextField
text.setText(label.getText());
event.consume();
});
getItems().add(item);
}
}
}
只需为每个标签创建一个不同的ContextMenu实例：
TextField text = new TextField();
Label label1 = new Label("hello");
Label label2 = new Label("world");
Label label3 = new Label("java");
label1.setContextMenu(createContextMenu(label1, text));
label2.setContextMenu(createContextMenu(label2, text));
label3.setContextMenu(createContextMenu(label3, text));
// ...
private ContextMenu createContextMenu(Label label, TextField text) {
ContextMenu menu = new ContextMenu();
MenuItem item = new MenuItem("copy to text field");
menu.getItems().add(item);
item.setOnAction(new EventHandler(){
public void handle(Event event) {
text.setText(label.getText());
}
});
return menu ;
}
我认为最简单的方法是将Node保存为上下文菜单的UserData。
EventHandler<? super ContextMenuEvent> eventHandle = e->menu.setUseData(e.getSource());
label1.setOnContextMenuRequested(eventHandle );
label2.setOnContextMenuRequested(eventHandle );
label3.setOnContextMenuRequested(eventHandle );
并在行动：
EventHandler<ActionEvent> menuItemEvent = e->{
Node node = (Node) ((MenuItem)e.getSource()).getParentPopup().getUserData();
...
};
总结基本要求：掌握打开contextMenu的节点。根据PopupWindow（ContextMenu的祖父母）的api文档，这应该很容易实现
...弹出窗口与指定的所有者节点相关联...
作为此弹出窗口所有者的节点。
因此，MenuItem动作的一般方法是
最后的例子只是在copyText中验证，它正在按预期工作...如果我们没有使用控件的contextMenuProperty。控件中不起作用的原因是ContextMenu的方法合同违规（可能是围绕textInputControls中的自动隐藏行为的introduced by a bug fix）：它在将contextMenu设置为任何控件之后总是使用show(Window w, ..)（实现细节：Control.contextMenuProperty）设置一个触发错误行为的标志setShowRelativeToWindow(true)）
现在我们可以做些什么来获取ownerNode？有几个选项，其中没有一个是好的：
show(Node owner, ... )并将给定的所有者保留在自定义属性中show(Node owner, ...) go dirty并反射性地将super ownerNode设置为给定的前两个引入额外的耦合，后者（除了脏反射访问）可能会重新引入自动隐藏的问题（“固定”行为本身就是脏的......违反了“keep-open-if-owner-clicked”保证）
最后，一个例子：
public class ContextMenuOwnerSO extends Application {
private Parent createContent() {
TextField text = new TextField();
// the general approach to grab a property from the Node
// that the ContextMenu was opened on
EventHandler<ActionEvent> copyText = e -> {
MenuItem source = (MenuItem) e.getTarget();
ContextMenu popup = source.getParentPopup();
String ownerText = "<not available>";
if (popup != null) {
Node ownerNode = popup.getOwnerNode();
if (ownerNode instanceof Labeled) {
ownerText = ((Label) ownerNode).getText();
} else if (ownerNode instanceof Text) {
ownerText = ((Text) ownerNode).getText();
}
}
text.setText(ownerText);
};
MenuItem printOwner = new MenuItem("copy to text field");
printOwner.setOnAction(copyText);
// verify with manual managing of contextMenu
Text textNode = new Text("I DON'T HAVE a contextMenu property");
Label textNode2 = new Label("I'm NOT USING the contextMenu property");
ContextMenu nodeMenu = new ContextMenu();
nodeMenu.getItems().addAll(printOwner);
EventHandler<ContextMenuEvent> openRequest = e -> {
nodeMenu.show((Node) e.getSource(), Side.BOTTOM, 0, 0);
e.consume();
};
textNode.setOnContextMenuRequested(openRequest);
textNode2.setOnContextMenuRequested(openRequest);
Label label1 = new Label("I'm USING the contextMenu property");
ContextMenu menu = new ContextMenu() {
// force menu to have an owner node: this being the case, it is not hidden
// on mouse events inside its owner
//@Override
//public void show(Node anchor, double screenX, double screenY) {
// ReadOnlyObjectWrapper<Node> owner =
// (ReadOnlyObjectWrapper<Node>)
// FXUtils.invokeGetFieldValue(PopupWindow.class, this, "ownerNode");
// owner.set(anchor);
// super.show(anchor, screenX, screenY);
//}
};
MenuItem item = new MenuItem("copy to text field");
menu.getItems().add(item);
item.setOnAction(copyText);
label1.setContextMenu(menu);
// same effect as forcing the owner node
// has to be done after the last setting of contextMenuProperty
// setting to true was introduced as fix for
// https://bugs.openjdk.java.net/browse/JDK-8114638
//FXUtils.invokeGetMethodValue(ContextMenu.class, menu, "setShowRelativeToWindow", Boolean.TYPE, false);
VBox content = new VBox(10, textNode, textNode2, text, label1);
return content;
}
@Override
public void start(Stage stage) throws Exception {
stage.setScene(new Scene(createContent(), 400, 200));
stage.setTitle(FXUtils.version());
stage.show();
}
public static void main(String[] args) {
launch(args);
}
@SuppressWarnings("unused")
private static final Logger LOG = Logger
.getLogger(ContextMenuOwnerSO.class.getName());
}