如何将按钮拖放到 GridPane 上？

Question

我正在创建一个简单的战舰游戏的学校项目，我想使用拖放功能将按钮从屏幕底部的 HBox 拖到玩家用来放置船只的 GridPane 上。但我无法让它正常工作。现在是picture of my board。

我尝试使用 button.setOnMouseDragged(e -> {CODE HERE});但它不起作用。

这是我用于窗口的代码

public class GridOrganizer {

    private BorderPane borderPane;

    public GridOrganizer() {
        borderPane = new BorderPane();
        borderPane.setStyle("-fx-background-color: grey;");
        borderPane.setPrefHeight(600);
        borderPane.setPrefWidth(600);
        createGrid();
    }

    public void createGrid() {
        //Creates the grids where the game is played and buttons/ships to place on grid

        GridPane playerGrid = new GridPane();
        GridPane enemyGrid = new GridPane();
        Insets padding = new Insets(10);

        //Create playergrid
        for (int i = 0; i < 10; i++) {
            playerGrid.getColumnConstraints().add(new ColumnConstraints(50)); //50 wide
            playerGrid.getRowConstraints().add(new RowConstraints(50)); 
        }
        //Create enemygrid
        for (int i = 0; i < 10; i++) {
            enemyGrid.getColumnConstraints().add(new ColumnConstraints(50)); //50 wide
            enemyGrid.getRowConstraints().add(new RowConstraints(50));
        }
        //looping through row and columns and adds buttons
        for (int i = 0; i < 10; i++) {
            for (int j = 0; j < 10; j++) {
                Button button = new Button();
                button.setPrefHeight(50);
                button.setPrefWidth(50);
                GridPane.setConstraints(button, j, i); //(button, column, row)
                playerGrid.getChildren().add(button); //add button on each index

                button.setOnAction(new EventHandler<ActionEvent>() {
                    @Override
                    public void handle(ActionEvent arg0) {
                        //HIT or MISS
                        System.out.println("Row: " + GridPane.getRowIndex(button) + ", Column: " + GridPane.getColumnIndex(button)); 
                        button.setStyle("-fx-background-color: grey;");
                    }
                });
            }
        }
        //..same with enemy grid
        for (int i = 0; i < 10; i++) {
            for (int j = 0; j < 10; j++) {
                Button button = new Button();
                button.setPrefHeight(50);
                button.setPrefWidth(50);
                GridPane.setConstraints(button, j, i); //(button, column, row)
                enemyGrid.getChildren().add(button); //add button on each index

                button.setOnAction(new EventHandler<ActionEvent>() {
                    @Override
                    public void handle(ActionEvent arg0) {
                        System.out.println("Row: " + GridPane.getRowIndex(button) + ", Column: " + GridPane.getColumnIndex(button)); 
                        button.setStyle("-fx-background-color: grey;");
                    }
                });
            }
        }

        //Make buttons for the ships
        Button rowboat = new Button("Rowboat");
        Button sailboat = new Button("Sailboat");
        Button submarine = new Button("Submarine");
        Button destroyer = new Button("Destroyer");
        Button battleship = new Button("Battleship");

        //Size the ship buttons to match game description
        battleship.setPrefHeight(50);
        battleship.setPrefWidth(250); //size 5
        destroyer.setPrefHeight(50);
        destroyer.setPrefWidth(200); //size 4
        submarine.setPrefHeight(50);
        submarine.setPrefWidth(150); //size 3
        sailboat.setPrefHeight(50);
        sailboat.setPrefWidth(150); //size 3
        rowboat.setPrefHeight(50);
        rowboat.setPrefWidth(100); //size 2

        //Drags button
        rowboat.setOnMouseDragged(e -> {
            //CODE HERE
        });

        //Drops button on grid
        //CODE HERE 


        sailboat.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent arg0) {
                //PLACE SHIP
            }
        });

        submarine.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent arg0) {
                //PLACE SHIP
            }
        }); 

        destroyer.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent arg0) {
                //PLACE SHIP
            }
        });

        battleship.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent arg0) {
                //PLACE SHIP
            }
        });

        HBox ships = new HBox(); //Horizontal box
        ships.getChildren().addAll(rowboat, sailboat, submarine, destroyer, battleship); //Add buttons to horizontal box

        //Add grids and ship buttons to pane with padding 
        borderPane.setLeft(enemyGrid); 
        BorderPane.setMargin(enemyGrid, padding);
        borderPane.setRight(playerGrid);
        BorderPane.setMargin(playerGrid, padding);
        borderPane.setBottom(ships);
        BorderPane.setMargin(ships, padding);
    }

    public Pane getGrid() {
        return borderPane;
    }
}

---

Answer 1

这里的计划是在拖动事件完成时使用创建按钮所需的数据启动拖动事件。在您的代码中，您似乎已经将Buttons 添加到Grid 中。这意味着您只需传输String 即可更改Button's 文本。在我的代码中，我在创建Grid 时使用了StackPane。然后我稍后创建并添加Buttons。你的方法可能会更好。我已经看过那么远了。我添加了一个 MCVE（来自 here 的更改代码）：

import javafx.application.Application;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.input.*;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.HBox;
import javafx.scene.layout.StackPane;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

/**
 * Demonstrates a drag-and-drop feature.
 */
public class HelloDragAndDrop extends Application
{

    @Override
    public void start(Stage stage)
    {
        //Source Buttons.
        final Button boat1 = new Button("boat1");
        final Button boat2 = new Button("boat2");
        final Button boat3 = new Button("boat3");
        final Button boat4 = new Button("boat4");

        //Adding OnDragDetected to source Buttons.
        setOnDragDetected(boat1);
        setOnDragDetected(boat2);
        setOnDragDetected(boat3);
        setOnDragDetected(boat4);

        //Adding onDragDone to source Buttons.
        setOnDragDone(boat1);
        setOnDragDone(boat2);
        setOnDragDone(boat3);
        setOnDragDone(boat4);

        //Creating GridPane
        GridPane gridPane = new GridPane();
        gridPane.setVgap(5);
        gridPane.setHgap(5);
        gridPane.setPadding(new Insets(5, 5, 5, 5));
        gridPane.setStyle("-fx-background-color: black;");
        //Adding StackPane to every Cell in the GridPane and Adding the Target Events to each StackPane.
        for (int i = 0; i < 6; i++) {
            StackPane stackPane = new StackPane();
            stackPane.setPrefSize(150, 50);
            stackPane.setStyle("-fx-background-color: yellow;");
            setOnDragOver(stackPane);
            setOnDragEntered(stackPane);
            setOnDragExited(stackPane);
            setOnDragDropped(stackPane);

            gridPane.add(stackPane, i / 3, i % 3);
        }

        HBox root = new HBox(new VBox(boat1, boat2, boat3, boat4), gridPane);
        stage.setTitle("Hello Drag And Drop");
        Scene scene = new Scene(root, 400, 200);
        stage.setScene(scene);
        stage.show();
    }

    public static void main(String[] args)
    {
        Application.launch(args);
    }

    //source events handlers
    public void setOnDragDetected(Button source)
    {
        source.setOnDragDetected((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();
        });
    }

    public void setOnDragDone(Button source)
    {
        source.setOnDragDone((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();
        });
    }

    //target event handlers
    public void setOnDragOver(StackPane target)
    {
        target.setOnDragOver((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();
        });
    }

    public void setOnDragEntered(StackPane target)
    {
        target.setOnDragEntered((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.setStyle("-fx-background-color: green;");
            }

            event.consume();
        });
    }

    public void setOnDragExited(StackPane target)
    {
        target.setOnDragExited((DragEvent event) -> {
            /* mouse moved away, remove the graphical cues */
            target.setStyle("-fx-background-color: transparent;");

            event.consume();
        });
    }

    public void setOnDragDropped(StackPane target)
    {
        target.setOnDragDropped((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());
                Button tempBoat = new Button(db.getString());
                tempBoat.setMaxSize(Double.MAX_VALUE, Double.MAX_VALUE);
                target.getChildren().clear();
                target.getChildren().add(tempBoat);
                success = true;
            }
            /* let the source know whether the string was successfully
            * transferred and used */
            event.setDropCompleted(success);

            event.consume();
        });
    }    
}

在此代码中，代表Boats 的Buttons 都附加了onDragDetected 和onDragDone 事件处理程序。它们被视为Source/拖动事件的开始。对于GridPane 中的每个单元格，都会添加一个StackPane。这些StackPanes 被认为是Target/ 放置拖动事件的区域。每个StackPane 都附加了onDragOver、onDragEntered、onDragDropped 和onDragExited。拖动事件完成后，接收该事件的StackPane/Target 将获得一个新的Button 作为与Source 同名的子级Button。