JavaFX拖放无法正常工作

Question

我在网格窗格中用两个ImageView做拖放测试。我的问题是，当我完成拖放并将目标imageview移动到源imageview并释放鼠标时，我错误地以显示“img2”中的图片而不是“img1”中的图片结束。当我注释掉“setOnDragExited”方法时，我最终得到了正确的图像“img1”，任何建议都将不胜感激。

import javafx.application.Application;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.input.*;
import javafx.scene.layout.GridPane;
import javafx.scene.paint.Color;
import javafx.stage.Stage;

public class Test extends Application
{
Image img1 = new Image("/graphics/hvid/hvidBonde.png");
Image hvidTom = new Image("/graphics/hvid/hvidTom.png");
Image sortTom = new Image("/graphics/sort/sortTom.png");
ImageView source = new ImageView(img1);
Image img2 = new Image("/graphics/sort/sortBonde.png");
ImageView target = new ImageView(img2);

GridPane root = new GridPane();

@Override
public void start(Stage primaryStage) throws Exception
{

    root.add(source, 1, 1);
    root.add(target, 2, 2);

    Scene scene = new Scene(root, 800, 800, Color.WHITE);
    primaryStage.setScene(scene);
    primaryStage.setResizable(false);
    primaryStage.show();

    source.setOnDragDetected(new EventHandler<MouseEvent>() {
        public void handle(MouseEvent event)
        {
            Dragboard db = source.startDragAndDrop(TransferMode.MOVE);
            ClipboardContent content = new ClipboardContent();
            content.putString(source.toString());
            db.setContent(content);
            event.consume();
        }
    });

    target.setOnDragOver(new EventHandler<DragEvent>() {
        public void handle(DragEvent event) {
            if (event.getGestureSource() != target &&
                    event.getDragboard().hasString())
            {
                event.acceptTransferModes(TransferMode.MOVE);
            }
            event.consume();
        }
    });

    target.setOnDragEntered(new EventHandler<DragEvent>() {
        public void handle(DragEvent event)
        {
            if (event.getGestureSource() != target &&
                    event.getDragboard().hasString())
            {
                target.setImage(source.getImage());
            }
            event.consume();
        }
    });

    target.setOnDragExited(new EventHandler<DragEvent>()
    {
        public void handle(DragEvent event)
        {
            target.setImage(img2);
            event.consume();
        }
    });

    target.setOnDragDropped(new EventHandler<DragEvent>() {
        public void handle(DragEvent event)
        {
            Dragboard db = event.getDragboard();
            boolean success = false;
            if (db.hasString())
            {
                target.setImage(source.getImage());
                success = true;
            }
            event.setDropCompleted(success);
            event.consume();
        }
    });

    source.setOnDragDone(new EventHandler<DragEvent>() {
        public void handle(DragEvent event)
        {
            if (event.getTransferMode() == TransferMode.MOVE)
            {

                source.setImage(hvidTom);

            }
            event.consume();
        }
    });
}

}

Answer 1

这是一个可以测试的示例应用程序。在我看来，不应该将事件处理程序放在ImageViews上。将它们放在图像视图所在的节点上。

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.input.ClipboardContent;
import javafx.scene.input.DragEvent;
import javafx.scene.input.Dragboard;
import javafx.scene.input.MouseEvent;
import javafx.scene.input.TransferMode;
import javafx.scene.layout.HBox;
import javafx.scene.layout.StackPane;
import javafx.scene.paint.Color;
import javafx.stage.Stage;

public class Test extends Application
{

    Image img1 = new Image("https://www.google.com/images/branding/googlelogo/1x/googlelogo_color_272x92dp.png");

    @Override
    public void start(Stage primaryStage) throws Exception
    {
        ImageView source = new ImageView();
        ImageView target = new ImageView();
        source.setImage(img1);

        StackPane stackPaneLeft = new StackPane(source);
        stackPaneLeft.setStyle("-fx-background-color: yellow");
        stackPaneLeft.setPrefSize(400, 800);

        stackPaneLeft.setOnDragDetected((MouseEvent event)
                -> {
            Dragboard db = source.startDragAndDrop(TransferMode.MOVE);
            ClipboardContent content = new ClipboardContent();
            content.putImage(source.getImage());
            db.setContent(content);
            event.consume();
        });

        stackPaneLeft.setOnDragDone((DragEvent event) -> {
            if (event.getTransferMode() == TransferMode.MOVE) {
                source.setImage(null);
            }
            event.consume();
        });

        StackPane stackPaneRight = new StackPane(target);
        stackPaneRight.setStyle("-fx-background-color: blue");
        stackPaneRight.setPrefSize(400, 800);

        stackPaneRight.setOnDragOver((DragEvent event)
                -> {
            if (event.getGestureSource() != target
                    && event.getDragboard().hasImage()) {
                event.acceptTransferModes(TransferMode.ANY);

            }
            event.consume();
        });

        stackPaneRight.setOnDragEntered((DragEvent event)
                -> {
            if (event.getGestureSource() != target
                    && event.getDragboard().hasImage()) {
                target.setImage(source.getImage());
            }
            event.consume();
        });

        stackPaneRight.setOnDragExited((DragEvent event)
                -> {
            if (target.getImage() != null && !event.isDropCompleted()) {
                target.setImage(null);
            }
            event.consume();
        });

        stackPaneRight.setOnDragDropped((DragEvent event)
                -> {
            Dragboard db = event.getDragboard();
            boolean success = false;
            if (db.hasImage()) {
                target.setImage(source.getImage());
                success = true;
            }
            event.setDropCompleted(success);
            event.consume();
        });

        HBox root = new HBox(stackPaneLeft, stackPaneRight);
        Scene scene = new Scene(root, 800, 800, Color.WHITE);
        primaryStage.setScene(scene);
        primaryStage.setResizable(false);
        primaryStage.show();

    }
}