JavaFX：在拖放期间处理KeyEvents？

Question

我有一个使用drag＆amp;的javafx应用程序滴（如本教程中所述）。当按下某个键或释放某个键时，该应用程序还使用钥匙文过滤器来更改其状态。

例如，我使用官方拖动的示例＆amp;删除教程并在开始方法期间添加以下处理程序：

public class HelloDragAndDrop extends Application {
    // ...
    @Override public void start(Stage stage) {
        // ...
        stage.addEventFilter(KeyEvent.KEY_PRESSED, event -> {
            if (event.getCode() == KeyCode.R)
                scene.setFill(Color.RED);
        });
        stage.addEventFilter(KeyEvent.KEY_RELEASED, event -> {
            if (event.getCode() == KeyCode.R)
                scene.setFill(Color.LIGHTGREEN);
        });
        // ...
    }
    // ...
}

通常，当我释放它时，这将使背景变成红色，然后再次固定R键和绿色。但这是问题：在阻力期间没有派出关键因素。下降动作。假设以下用户操作：

1. 用户按R->背景转弯
2. 用户开始拖动
3. 用户发布r->背景仍然是红色
4. 用户完成拖动 ->背景仍然是红色

回到常规颜色的唯一方法是再次按下R。

主要问题：是否有任何方法可以在拖放操作中接收这些关键？

workaroundquestion：如果我必须处理这些关键因素可能会"丢失"的事实 - 有没有办法做类似boolean isKeyDown(KeyCode keyCode)之类的事情，这样我至少可以在Drag＆amp; Drop Action完成后至少调整应用程序的状态？

（P.S。：这与该问题与拖放的问题不同，而该问题与一般阻力手势有关。）

Answer 1

我会将其作为评论，但不幸的是我缺乏声誉 - 使用以下代码，我可以执行您建议的操作顺序，但是在步骤3中，背景切换回绿色。这已经解决了您的问题吗？我想这与活动处理程序的位置有关。不起作用的是启动拖动和按R，就像我这样做的那样保持背景。

import javafx.application.Application;
import javafx.event.EventHandler;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.input.*;
import javafx.scene.paint.Color;
import javafx.scene.text.Text;
import javafx.stage.Stage;
/**
 * Demonstrates a drag-and-drop feature.
 */
public class HelloDragAndDrop extends Application {
    @Override public void start(Stage stage) {
        stage.setTitle("Hello Drag And Drop");
        Group root = new Group();
        Scene scene = new Scene(root, 400, 200);
        scene.setFill(Color.LIGHTGREEN);
        final Text source = new Text(50, 100, "DRAG ME");
        source.setScaleX(2.0);
        source.setScaleY(2.0);
        final Text target = new Text(250, 100, "DROP HERE");
        target.setScaleX(2.0);
        target.setScaleY(2.0);
        stage.addEventFilter(KeyEvent.KEY_PRESSED, event -> {
            if (event.getCode() == KeyCode.R)
                scene.setFill(Color.RED);
        });
        stage.addEventFilter(KeyEvent.KEY_RELEASED, event -> {
            if (event.getCode() == KeyCode.R)
                scene.setFill(Color.LIGHTGREEN);
        });
        source.setOnDragDetected(new EventHandler <MouseEvent>() {
            public void handle(MouseEvent event) {
                /* drag was detected, start drag-and-drop gesture*/
                System.out.println("onDragDetected");
                /* allow any transfer mode */
                Dragboard db = source.startDragAndDrop(TransferMode.ANY);
                /* put a string on dragboard */
                ClipboardContent content = new ClipboardContent();
                content.putString(source.getText());
                db.setContent(content);
                event.consume();
            }
        });
        target.setOnDragOver(new EventHandler <DragEvent>() {
            public void handle(DragEvent event) {
                /* data is dragged over the target */
                System.out.println("onDragOver");
                /* accept it only if it is  not dragged from the same node 
                 * and if it has a string data */
                if (event.getGestureSource() != target &&
                        event.getDragboard().hasString()) {
                    /* allow for both copying and moving, whatever user chooses */
                    event.acceptTransferModes(TransferMode.COPY_OR_MOVE);
                }
                event.consume();
            }
        });
        target.setOnDragEntered(new EventHandler <DragEvent>() {
            public void handle(DragEvent event) {
                /* the drag-and-drop gesture entered the target */
                System.out.println("onDragEntered");
                /* show to the user that it is an actual gesture target */
                if (event.getGestureSource() != target &&
                        event.getDragboard().hasString()) {
                    target.setFill(Color.GREEN);
                }
                event.consume();
            }
        });
        target.setOnDragExited(new EventHandler <DragEvent>() {
            public void handle(DragEvent event) {
                /* mouse moved away, remove the graphical cues */
                target.setFill(Color.BLACK);
                event.consume();
            }
        });
        target.setOnDragDropped(new EventHandler <DragEvent>() {
            public void handle(DragEvent event) {
                /* data dropped */
                System.out.println("onDragDropped");
                /* if there is a string data on dragboard, read it and use it */
                Dragboard db = event.getDragboard();
                boolean success = false;
                if (db.hasString()) {
                    target.setText(db.getString());
                    success = true;
                }
                /* let the source know whether the string was successfully 
                 * transferred and used */
                event.setDropCompleted(success);
                event.consume();
            }
        });
        source.setOnDragDone(new EventHandler <DragEvent>() {
            public void handle(DragEvent event) {
                /* the drag-and-drop gesture ended */
                System.out.println("onDragDone");
                /* if the data was successfully moved, clear it */
                if (event.getTransferMode() == TransferMode.MOVE) {
                    source.setText("");
                }
                event.consume();
            }
        });
        root.getChildren().add(source);
        root.getChildren().add(target);
        stage.setScene(scene);
        stage.show();
    }
    public static void main(String[] args) {
        Application.launch(args);
    }
}