如何在 Java 中将多个可拖动图像添加到 JFrame？

Posted 2023-05-08

【中文标题】如何在 Java 中将多个可拖动图像添加到 JFrame？

【英文标题】：How to add multiple draggable images to a JFrame in Java?

【发布时间】：2017-07-13 00:17:05

【问题描述】：

我对我的 java 代码有疑问。我的目标是制作一个 JFrame，在其中我可以有多个可拖动的图像，它们可以捕捉到一个网格。

问题：

我只能添加一个可拖动的图像。拖动和捕捉到网格工作正常。一旦我尝试向 JFrame 添加更多可拖动图像（我尝试在 MainScreen.java 文件底部附近执行此操作），它只会显示我添加的 最后一个。

守则：

MainScreen.java

package systematics;

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Image;
import java.awt.Toolkit;
import java.util.ArrayList;

import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JPanel;

public class MainScreen extends JFrame 

    private static Image img = Toolkit.getDefaultToolkit().getImage("C:/Users/lenar_000/Pictures/splitter skin.png");
    public static JFrame main = new JFrame();
    public static Dimension screensize = Toolkit.getDefaultToolkit().getScreenSize();
    public static JPanel content = new JPanel();
    public static JMenuBar menubar = new JMenuBar();
    public static ArrayList<JMenuItem> menuitem = new ArrayList<JMenuItem>();
    public static ArrayList<JMenu> menu = new ArrayList<JMenu>(20);
    public static ArrayList<JComponent> gates = new ArrayList<JComponent>();
    public static componentGate gate = new componentGate(0, 1, 1, null);
    public static int imageWidth = 60, imageHeight = 60, imageX, imageY, gridw = 10, gridh = 10;
    public static DragImage componentimage = new DragImage(img, 300, 300, 200, 200);
    public static DragImage componentimage1 = new DragImage(img, 50, 50, 50, 50);

    public static JFrame createmain()      
        //location and size of the window
        main.setJMenuBar(createmenu());
        main.setExtendedState(JFrame.MAXIMIZED_BOTH); 
        int w = (int) screensize.getWidth();
        int h = (int) screensize.getHeight();
        main.setSize((int) (w / 2), (int) (h / 2));
        int w1 = (int) main.getSize().getWidth();
        int h1 = (int) main.getSize().getHeight();
        int x = (screensize.width-w1)/2;
        int y = (screensize.height-h1)/2;
        main.setLocation(x, y);

        //other stuff
        main.setVisible(true);
        main.setTitle("systematic");
        main.setDefaultCloseOperation(EXIT_ON_CLOSE);
        return main;
    

    //unused
    public static JPanel createcontent() 
        content.setBackground(Color.DARK_GRAY);
        content.setVisible(true);
        content.setOpaque(true);
        return content ;
    

    //to make the menubar
    public static JMenuBar createmenu() 

        //add the items to the arrays which hold the menu's and the menuitems
        menu.add(0, new JMenu());
        menu.add(1, new JMenu());
        menu.add(2, new JMenu());
        menuitem.add(0, new JMenuItem());
        menuitem.add(1, new JMenuItem());
        menuitem.add(2, new JMenuItem());

        //some settings for the menubar
        menubar.setOpaque(true);
        menubar.setVisible(true);
        menubar.setBackground(new Color(255, 255, 255));



        //adding the first menu which contains a submenu
        menu.get(0).setText("File");
        menu.get(0).setOpaque(true);
        menu.get(0).setBackground(new Color(255, 255, 255));
        menubar.add(menu.get(0), 0);

        menuitem.get(0).setText("new file");
        menuitem.get(0).setToolTipText("creates and opens a new file");
        menuitem.get(0).setOpaque(true);
        menuitem.get(0).setBackground(new Color(255, 255, 255));
        menu.get(0).add(menuitem.get(0), 0);



        //adding the second menu which contains a submenu
        menu.get(1).setText("Toolbars");
        menu.get(1).setOpaque(true);
        menu.get(1).setBackground(new Color(255, 255, 255));
        menubar.add(menu.get(1), 1);

        menuitem.get(1).setText("components");
        menuitem.get(1).setToolTipText("toggle for the components toolbar");
        menuitem.get(1).setOpaque(true);
        menuitem.get(1).setBackground(new Color(255, 255, 255));
        menu.get(1).add(menuitem.get(1), 0);



        //adding the third menu which contains a submenu
        menu.get(2).setText("Toolbars");
        menu.get(2).setOpaque(true);
        menu.get(2).setBackground(new Color(255, 255, 255));
        menubar.add(menu.get(2), 2);

        menuitem.get(2).setText("components");
        menuitem.get(2).setToolTipText("toggle for the components toolbar");
        menuitem.get(2).setOpaque(true);
        menuitem.get(2).setBackground(new Color(255, 255, 255));
        menu.get(2).add(menuitem.get(2), 0);


        return menubar;
    


    public static void main(String[] args) 
        createmain();
        //creategrid();
        main.getContentPane().add(componentimage, 0);
        main.getContentPane().add(componentimage1, 1);

    

    //unused
    private static void creategrid() 
        DrawingLine line1 = new DrawingLine();
        main.getContentPane().add(line1,-1);

    

    private static final long serialVersionUID = 1L;

拖动图像

package systematics;

import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;

import javax.swing.JComponent;

public class DragImage extends JComponent implements MouseMotionListener, MouseListener 

    private static final long serialVersionUID = 1L;
    private int imageWidth, imageHeight, gridw = 50, gridh = 50, imageX/* = gridw / 2 - imageWidth / 2*/, imageY/* = gridh / 2 - imageHeight / 2*/, onObject, checked;

    private Image image;

    DragImage(Image i, int imgX, int imgY, int imagewidth, int imageheight) 
        this.imageWidth = imagewidth;
        this.imageHeight = imageheight;
        this.imageX = imgX;
        this.imageY = imgY;
        this.image = i.getScaledInstance(imageWidth, imageHeight, 0);
        addMouseMotionListener(this);
        addMouseListener(this);
    

    public void mouseDragged(MouseEvent e) 
        //first checking if "onObject" is 1 to make sure that the mouse is on the image when it started dragging
        if(this.onObject == 1) 
            if((int) (Math.floor(e.getX() / this.gridw) * this.gridw + (this.gridw / 2) - (this.imageWidth / 2)) != this.imageX || (int) (Math.floor(e.getY() / this.gridh) * this.gridh + (this.gridh / 2) - (this.imageHeight / 2)) != this.imageY) 
                this.imageX = (int) (Math.floor(e.getX() / this.gridw) * this.gridw + (this.gridw / 2) - (this.imageWidth / 2));
                this.imageY = (int) (Math.floor(e.getY() / this.gridh) * this.gridh + (this.gridh / 2) - (this.imageHeight / 2));
                this.repaint();
            
        
    

    public void paint(Graphics g) 
        Graphics2D g2 = (Graphics2D) g;
        //repainting the object that you are dragging at the new location, which is determined by the math in "mouseDragged"
        g2.drawImage(this.image, this.imageX, this.imageY, this);
    

    @Override
    public void mousePressed(MouseEvent e) 
        // TODO Auto-generated method stub
        //this checks if the mouse is on the object when you start dragging, for the method mouseDragged runs when you drag, regardless of the mouse position
        System.out.println("");
        System.out.println("pressed, checked is now: " + this.checked);
        if(this.checked == 0 && (e.getX() >= this.imageX) && (e.getY() >= this.imageY) && (e.getX() <= this.imageX + (this.imageWidth)) && (e.getY() <= this.imageY + (this.imageHeight))) 
            this.onObject = 1;
            System.out.println("onObject: " + this.onObject);
        
        //checked is a parameter, which is used to make sure that this method doesn't run all the time, but only when the mouse started dragging
        this.checked = 1;
        System.out.println("checked: " + this.checked);
    

    @Override
    public void mouseReleased(MouseEvent e) 
        // TODO Auto-generated method stub
        System.out.println("");
        System.out.println("released, checked is now: " + this.checked);
        this.onObject = 0;
        System.out.println("onObject: " + this.onObject);
        //setting checked to 0 when the mouse stops dragging, so when it starts dragging, it can check wether the mouse is on the image yes or no
        checked = 0;
        System.out.println("checked: " + this.checked);
    


    //some unused implemented methods
    @Override
    public void mouseMoved(MouseEvent e) 
        // TODO Auto-generated method stub

    

    @Override
    public void mouseClicked(MouseEvent e) 
        // TODO Auto-generated method stub

    

    @Override
    public void mouseEntered(MouseEvent e) 
        // TODO Auto-generated method stub

    

    @Override
    public void mouseExited(MouseEvent e) 
        // TODO Auto-generated method stub

    

顺便说一句，我为捕捉到网格的数学感到非常自豪:)

高度赞赏任何解决方案

【问题讨论】：

您可能想在此处查看 Draggable（用于在容器中拖动组件）：sourceforge.net/p/tus/code/HEAD/tree/tjacobs/ui/drag

我似乎已经解决了这个问题，我不太清楚如何解决，但我认为是 JPanel 的布局。我做了： main.getContentPane().setLayout(new BorderLayout());我不确定那是它起作用的原因，这是一段时间前的事了。

【参考方案1】：

我可以在其中拥有多个可拖动的图像，它们会对齐网格。

最简单的方法是使用 JLabel 来显示图像。然后将监听器添加到标签以支持拖动。

首先，您需要使用空布局将 JLabel 添加到面板。然后，您将标签添加到面板并手动管理标签的大小/位置。您可以使用Drag Layout 来帮助您管理此问题。

接下来，您需要能够在面板周围拖动组件。您可以查看Moving Windows 中的ComponentMover 类。它支持拖动组件并将组件捕捉到网格。

【参考方案2】：

JFrame 的 contentPane 的默认布局是 BorderLayout。你在做

    main.getContentPane().add(componentimage, 0);
    main.getContentPane().add(componentimage1, 1);

第二个参数应该是 BorderLayout.CENTER、BorderLayout.NORTH 等之一。

但是您的另一个问题是 DragImage.getPreferredSize() 将返回 (0,0)，因为您没有向其中添加任何内容。您需要覆盖 getPreferredSize 或在 DragImages 上使用 setPreferredSize 以便在 ContentPane 中为它们分配空间。

【讨论】：

好的，所以我将 main.getContentPane().add(componentimage, 0) 更改为 main.getContentPane().add(componentimage, 1)，然后我做了 setpreferredsize 的事情，但是，当我尝试添加多张图片时，它只显示最后一张。