在JFrame中拖动JPanel

Question

我加入JPanel到JFrame一个JButton点击.它增加JPanel了框架.该按钮将继续添加JPanelto JFrameon click事件.没有限制.单击按钮时,我也会添加JPanels到a List.我这样做是因为添加了MouseMotionListenerfor循环来处理拖拽JPanel的问题.

我现在面临的问题是阻力.当我JPanel通过单击添加第一个并且如果我拖动它时,它正确地跟随鼠标光标坐标.当我添加一秒钟时JPanel,它也完全跟随鼠标.添加第二个后,如果尝试拖动第一个JPanel,第一个JPanel似乎遵循不同的坐标,初始位置将更改为其他位置.我不知道我在哪里犯了这个错误.请帮我解决这个问题.请仔细阅读以下代码.

import java.awt.Color;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionAdapter;
import java.util.ArrayList;
import java.util.List;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;


public class MyFrame extends JFrame {

    JButton jb;
    List<JPanel> mypanels = new ArrayList<JPanel>();
    public MyFrame() {
        jb = new JButton("Add Panel");
        jb.setBounds(10, 10, 100, 50);
        setSize(new Dimension(1000, 600));
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLayout(null);
        add(jb);
        setVisible(true);
        initialize();
    }


    public void initialize() {

        jb.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent arg0) {
                // TODO Auto-generated method stub
                JPanel panel = new JPanel();
                panel.setBounds(150,150,200,200);
                panel.setBackground(Color.black);
                mypanels.add(panel);
                add(panel);
                repaint();
                handleDrag();
            }
        });

    }

    public void handleDrag(){
        for(int i=0;i<mypanels.size();i++) {
            final int j = i;
            mypanels.get(i).addMouseMotionListener(new MouseMotionAdapter() {

                @Override
                public void mouseDragged(MouseEvent me) {
                    me.translatePoint(me.getComponent().getLocation().x, me.getComponent().getLocation().y);
                    mypanels.get(j).setLocation(me.getX(), me.getY());
                }

            });
        }
    }

    public static void main(String args[]) {

        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                // TODO Auto-generated method stub
                new MyFrame();
            }
        });

    }


}

Answer 1

看起来你的handleDrag方法是在只有一个JPanel添加到List时为每个JPanel添加一个新的匿名监听器.只需要添加一次监听器,如果添加了多个监听器,则行为将变得奇怪.

这是一个更新的handleDrag方法

    public void handleDrag(JPanel panel){
    final JPanel p = panel;
        panel.addMouseMotionListener(new MouseMotionAdapter() {

            @Override
            public void mouseDragged(MouseEvent me) {
                me.translatePoint(me.getComponent().getLocation().x, me.getComponent().getLocation().y);
                p.setLocation(me.getX(), me.getY());
            }

        });
}

Answer 2

Joe是正确的,这是我在我的项目中使用handleDrag方法:

public void handleDrag(final JPanel panel){
    panel.addMouseListener(new MouseAdapter() {
        @Override
        public void mousePressed(MouseEvent me) {
             x = me.getX();
             y = me.getY();
        }
    });
    panel.addMouseMotionListener(new MouseMotionAdapter() {
        @Override
        public void mouseDragged(MouseEvent me) {
            me.translatePoint(me.getComponent().getLocation().x-x, me.getComponent().getLocation().y-y);
            panel.setLocation(me.getX(), me.getY());
        }
    });
}

这样,面板在点击时不会进行初始"跳跃".