Question

我想在listView的行上使用上下文菜单项。在listView的MOUSE_CLICKED事件的事件处理程序中，getSelectionModel（）。getSelectedItem（）返回所选项，即好。但是，当我处理contextMenuItem的onAction事件时，它返回null。但是，图形化地选择了该项目。有没有办法在第一次事件处理后“保留”选择？

以下是代码的相关部分：

    ListView<Text> nameList = new ListView<>();
    final ContextMenu cCm = new ContextMenu();
    MenuItem cItem = new MenuItem("someText");
    cCm.getItems().add(cItem);

...

nameList.addEventHandler(MouseEvent.MOUSE_CLICKED, new EventHandler<MouseEvent>() {

        @Override
        public void handle(MouseEvent e) {
            if (e.getButton() == MouseButton.SECONDARY) {
                    //its OK here:
                    System.out.println(nameList.getSelectionModel().getSelectedItem().getText());
                    cCm.show(nameList, e.getScreenX(), e.getScreenY());
            }
        }
    });

    cItem.setOnAction(new EventHandler<ActionEvent>() {

        @Override
        public void handle(ActionEvent e) {
            final Stage dialog = new Stage();
            dialog.initModality(Modality.WINDOW_MODAL);
            //nullPointerException on the following:
            Text t = new Text(nameList.getSelectionModel().getSelectedItem().getText());
            //showing dialog, etc.

Answer 1

我几乎创建了你所做的完全复制品，我的实现工作：

private void initRandomCardListView() {
    populateRandomList();
    final ContextMenu randomListContextMenu = new ContextMenu();
    MenuItem replaceCardMenuItem = new MenuItem("Replace");
    replaceCardMenuItem.setOnAction(new EventHandler<ActionEvent>() {
        @Override
        public void handle(ActionEvent event) {
            replaceRandomCard();
        }
    });
    randomListContextMenu.getItems().add(replaceCardMenuItem);

    randomCardList.addEventHandler(MouseEvent.MOUSE_CLICKED, new EventHandler<MouseEvent>() {
        @Override
        public void handle(MouseEvent event) {
            if (event.getButton().equals(MouseButton.SECONDARY)) {
                randomListContextMenu.show(randomCardList, event.getScreenX(), event.getScreenY());
            }
        }
    });
}

private void replaceRandomCard() {
    System.out.println("jobs done");
    System.out.println("card selected: " + randomCardList.selectionModelProperty().get().getSelectedItem().toString());
    System.out.println("card index: " + randomCardList.getSelectionModel().getSelectedIndex());
    System.out.println("card index: " + randomCardList.getSelectionModel().getSelectedItem().toString());
}

我没有任何空指针异常。总的来说，您的实施看起列表视图中的项目很可能出现问题。

JavaFX ListView＆amp; ContextMenu - getSelectedItem（）返回null

1 个答案: