Question

我正在尝试向多个节点添加一个事件处理程序，这是onDragDetected事件。但是当我在一个循环中分配它时，它似乎没有注册它。我正在使用的代码如下所示：

import java.util.ArrayList;

import javafx.application.Application;
import javafx.event.EventHandler;
import javafx.scene.Group;
import javafx.scene.Scene;
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.BorderPane;
import javafx.scene.layout.FlowPane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Rectangle;
import javafx.scene.text.Text;
import javafx.stage.Screen;
import javafx.stage.Stage;

public class DragAndDrop extends Application {
    Group page1,page2;
    ArrayList<Group> pages;
    FlowPane bottom;
    public static void main(String[] args) {
        launch();
    }

    @Override
    public void start(Stage stage) throws Exception {
        pages = new ArrayList<Group>();
        stage.setTitle("scale test");
        BorderPane border = new BorderPane();
        Group root = new Group();
        bottom = new FlowPane();
        bottom.setMinSize(Screen.getPrimary().getVisualBounds().getWidth(), 200);
        //bottom.setStyle("-fx-background-color: grey");
        page1 = new Group();
        page2 = new Group();
        Rectangle r = new Rectangle(0,0,200, 200);
        Rectangle r2 = new Rectangle(205,0,200,200);
        Text t = new Text(
                "asodjoijdjiasjdoijaisjd\nijasijdiajsidjoias\njiodjiajosijdiojaisjdoijaoisjdiojaoisjdjaoisjdiojsoidj\njdoasijdoajsoidjoaisjoidjaoisjdiojs");
        t.setFill(Color.FLORALWHITE);
        t.setWrappingWidth(180);
        t.setLayoutX(10);
        t.setLayoutY(20);
        Text t2 = new Text(
                "asodjoijdjiasjdoijaisjdijasijdiajsidjoiasjiodjiajosijdiojaisjdoijaoisjdiojaoisjdjaoisjdiojsoidj\njdoasijdoajsoidjoaisjoidjaoisjdiojs");
        t2.setFill(Color.FLORALWHITE);
        t2.setWrappingWidth(180);
        t2.setX(r2.getX()+10);
        t2.setY(r2.getY()+20);
        page1.getChildren().addAll(r, t);
        page2.getChildren().addAll(r2,t2);
        setDrag();
        root.getChildren().addAll(page1,page2);
        pages.add(page1);
        pages.add(page2);
        border.setCenter(root);
        border.setBottom(bottom);
        Scene scene = new Scene(border, 800, 700);
        stage.setScene(scene);
        stage.show();
    }

    private void createPage(String s){
        Group page = new Group();
        Rectangle rect = new Rectangle(200,200);
        Text text = new Text(
                "asodjoijdjiasjdoijaisjdijasijdiajsidjoiasjiodjiajosijdiojaisjdoijaoisjdiojaoisjdjaoisjdiojsoidj\njdoasijdoajsoidjoaisjoidjaoisjdiojs");
        text.setFill(Color.FLORALWHITE);
        text.setText(s);
        text.setWrappingWidth(180);
        text.setX(rect.getX()+10);
        text.setY(rect.getY()+20);
        page.getChildren().addAll(rect,text);
        bottom.getChildren().add(page);
    }

    private void setDrag(){
        int pagenum = 0;
        while(pagenum<pages.size()){
            final Group page = pages.get(pagenum);
            page.setOnDragDetected(new EventHandler <MouseEvent>() {
                public void handle(MouseEvent event) {
                    Dragboard drag = page.startDragAndDrop(TransferMode.ANY);
                    ClipboardContent content = new ClipboardContent();
                    content.putString(((Text) page.getChildren().get(1)).getText());
                    drag.setContent(content);

                    event.consume();
                }
            });
            pagenum++;
        }/*
        page1.setOnDragDetected(new EventHandler <MouseEvent>() {
            public void handle(MouseEvent event) {
                Dragboard drag = page1.startDragAndDrop(TransferMode.ANY);
                ClipboardContent content = new ClipboardContent();
                content.putString(((Text) page1.getChildren().get(1)).getText());
                drag.setContent(content);

                event.consume();
            }
        });

        page2.setOnDragDetected(new EventHandler <MouseEvent>() {
            public void handle(MouseEvent event) {
                Dragboard drag = page2.startDragAndDrop(TransferMode.ANY);
                ClipboardContent content = new ClipboardContent();
                content.putString(((Text) page2.getChildren().get(1)).getText());
                drag.setContent(content);

                event.consume();
            }
        });*/

        bottom.setOnDragOver(new EventHandler <DragEvent>() {
            public void handle(DragEvent event) {
                /* data is dragged over the target */

                /* accept it only if it is  not dragged from the same node 
                 * and if it has a string data */
                if (event.getGestureSource() != bottom &&
                        event.getDragboard().hasString()) {
                    /* allow for both copying and moving, whatever user chooses */
                    event.acceptTransferModes(TransferMode.COPY_OR_MOVE);
                }

                event.consume();
            }
        });

        bottom.setOnDragEntered(new EventHandler <DragEvent>() {
            public void handle(DragEvent event) {
                /* show to the user that it is an actual gesture target */
                if (event.getGestureSource() != bottom &&
                        event.getDragboard().hasString()) {
                    bottom.setStyle("-fx-background-color: green");
                }

                event.consume();
            }
        });

        bottom.setOnDragExited(new EventHandler <DragEvent>() {
            public void handle(DragEvent event) {
                /* mouse moved away, remove the graphical cues */
                bottom.setStyle("-fx-background-color: grey");

                event.consume();
            }
        });

        bottom.setOnDragDropped(new EventHandler <DragEvent>() {
            public void handle(DragEvent event) {
                /* if there is a string data on dragboard, read it and use it */
                Dragboard db = event.getDragboard();
                boolean success = false;
                if (db.hasString()) {
                    createPage(db.getString());
                    success = true;
                }
                /* let the source know whether the string was successfully 
                 * transferred and used */
                event.setDropCompleted(success);

                event.consume();
            }
        });
    }

}

任何帮助将不胜感激。感谢

Answer 1

在将网页添加到列表setDrag()之前，您正在调用ArrayList<Group> pages方法。在行pages.add(page2);

之后调用它

Answer 2

您不是创建一个事件处理程序，而是多个事件处理程序。 new运算符创建一个新对象。

 while(pagenum<pages.size()){
        final Group page = pages.get(pagenum);
        page.setOnDragDetected(new EventHandler <MouseEvent>() {
            ...

在while循环

之前创建事件处理程序

EventHandler eh = new EventHandler <MouseEvent>() {
   ...
};

并应用它

while(pagenum<pages.size()){
        final Group page = pages.get(pagenum);
        page.setOnDragDetected(eh);
        ...

在循环中添加事件处理程序

2 个答案: