java - 实现从一个 JPanel 拖放到另一个 JPanel

Question

我是 Swing 中拖放的新手。我有一个JPanel可以绘制带有叠加在其上的标题的图像。我想在这个上实现拖放JPanel，但是在浏览了一些文档和教程之后，我没有找到任何关于如何为这种类型的组件完成的可用指针。对于初学者来说，它没有setDragEnabled功能。

我可以做一个JPanel可拖动的吗？我想使用这个 DnD 操作将某个对象的引用从一个面板传递到另一个面板。

Answer 1

您可以在任何JComponent. 见setTransferHandler方法。

该setDragEnabled方法通常在可以在 JDK 中实现良好默认 D&D 行为的组件上提供。在这种情况下，您可以通过调用该方法来激活默认的 D&D。

JPanel他们（= Swing 开发人员）可能想不出任何像样的默认 D&D 行为，因此您必须实现自己的TransferHandler. 我强烈建议在开始之前阅读拖放教程

Answer 2

可能这可以帮助你。

Java中复杂自定义对象的拖放

Answer 3

我不知道听起来有多可行，但是当我需要拖放面板时，我是这样做的：

Firstable 我为可拖动的面板和容器实现了动作事件，它既可以是

我为选定的父级、选定的子级和当前面板使用了静态变量

当鼠标悬停在面板上时，您将其设置为当前面板

当您单击时，鼠标按下，无论如何，您检查 currentpanel 是否是被点击的面板并设置为子面板

当鼠标在面板上且子面板不为空时，似乎您正在拖动，一旦您释放鼠标，当前面板将变为父面板

你必须添加一些验证。

如果正在拖动面板，您可以使用自己的实现，它可以跟随鼠标坐标或仅突出显示它并突出显示父级，我使用最后一个选项来模拟拖动

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好的，我写了这个，太有问题了，但这就是想法：

import java.awt.Color;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.Rectangle;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JDesktopPane;
import javax.swing.JFrame;
import javax.swing.JTextField;

/**
 *
 * @author porfiriopartida
 */
public class DraggablePanel extends JDesktopPane implements ContainerPanel{
    public ContainerPanel parent;

    static DraggablePanel over;
    static ContainerPanel overParent;
    static DraggablePanel dragging;
    static ContainerPanel draggingParent;

    public DraggablePanel(){
        this(null);
    }
    public DraggablePanel(ContainerPanel parent){
        this.parent = parent;
        setBorder(BorderFactory.createLineBorder(Color.black));
        setBounds(0,0,100,100);

        if(parent != null)
            addMouseListener(new MouseAdapter(){
            @Override
            public void mouseEntered(MouseEvent me) {
                DraggablePanel src = (DraggablePanel) me.getSource();
                DraggablePanel.over = src;
                DraggablePanel.overParent = DraggablePanel.over.parent;
            }

            @Override
            public void mouseExited(MouseEvent me) {

            }

            @Override
            public void mouseReleased(MouseEvent me) {
                if(DraggablePanel.over != null && DraggablePanel.dragging != null && DraggablePanel.overParent != null){
                    Rectangle bounds = DraggablePanel.dragging.getBounds();
                    bounds.x = me.getX();
                    bounds.y = me.getY();

                    //Remove child from parent
                    DraggablePanel.dragging.parent.removePanel(DraggablePanel.dragging);

                    if(DraggablePanel.dragging.parent != DraggablePanel.overParent){
                        //add child to new parent
                        DraggablePanel.overParent.addPanel(DraggablePanel.dragging, bounds);
                    }
                    else{
                        //same parent selected
                        DraggablePanel.dragging.parent.addPanel(DraggablePanel.dragging, bounds);
                    };
                    DraggablePanel.dragging.parent = DraggablePanel.overParent;
                }

                //cleaning variables
                DraggablePanel.dragging = null;
                DraggablePanel.over = null;
                DraggablePanel.draggingParent = null;
                DraggablePanel.overParent = null;

            }

            @Override
            public void mousePressed(MouseEvent me) {
                DraggablePanel.dragging = (DraggablePanel) me.getSource();
                DraggablePanel.draggingParent = DraggablePanel.dragging.parent;
            }
        });

        addMouseListener(new MouseAdapter() {
            @Override
            public void mouseEntered(MouseEvent me) {
                super.mouseEntered(me);
                ContainerPanel src = (ContainerPanel) me.getSource();
                DraggablePanel.overParent = src;
                if (DraggablePanel.draggingParent == null || DraggablePanel.draggingParent == src) {
                    setBorder(BorderFactory.createLineBorder(Color.BLACK, 2));
                } else {
                    setBorder(BorderFactory.createLineBorder(Color.blue, 2));
                }
            }

            @Override
            public void mouseExited(MouseEvent me) {

            }

            @Override
            public void mouseReleased(MouseEvent me) {
            }
        });
    }

    @Override
    public void addPanel(DraggablePanel panel) {
        panel.parent = this;
        add(panel);

            repaint();
            revalidate();

            try {
            getParent().repaint();
        } catch (Exception e) {
        }

    }
    @Override
    public void addPanel(DraggablePanel panel, Rectangle bounds) {
        setBounds(bounds);
        addPanel(panel);
    }

    @Override
    public void removePanel(DraggablePanel panel) {
        remove(panel);
    }



    public static void main(String args[]){
        JFrame frame = new JFrame();
        frame.setLayout(new GridLayout(1,1));
        JTextField tf = new JTextField("textfield");
        JButton btn = new JButton("Button");

        DraggablePanel desktop = new DraggablePanel();
        frame.add(desktop);

        DraggablePanel p1 = new DraggablePanel(desktop);
        p1.setLayout(new GridLayout(2,1));
        p1.add(tf);
        p1.setBounds(0,0,100,50);
        tf.setBounds(5,5,80,30);

        DraggablePanel p2 = new DraggablePanel(desktop);
        p2.setLayout(new GridLayout(2,1));
        p2.add(btn);
        p2.setBounds(50,50,50,30);
        btn.setBounds(5,5,30,20);

        desktop.add(p1);
        desktop.add(p2);

        frame.setPreferredSize(new Dimension(600,400));
        frame.pack();
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
}