在 Java 中使用 Swing 显示图像

Question

我一直在爬取 Oracle 和 Stack Overflow 试图找到解决我的问题的方法，但我没有找到我要找的东西。

下面我有两个 classes，目前所有程序需要做的是允许用户使用 JFileChooser 打开图像文件并在 GUI 中显示它（所以稍后可以对其进行一些图像处理）

我已经测试了代码执行到我知道ImageGUI class中的变量img正在被初始化为第99行我想要的图片。我的问题在我 pack(); 之前让图像显示在 GUI 中。

我错过了什么？

 public class ImageEditLaunch {

public static void main(String[] args) {
    ImageEditEngine program = new ImageEditEngine();

}

}

import java.awt.image.BufferedImage;
import java.io.File;

import javax.imageio.ImageIO;
import javax.swing.ImageIcon;

public class ImageEditEngine {

    private static int[][][] originalImage;
    private static BufferedImage originalImageBuffer;

    public ImageEditEngine() {
        originalImage = new int[0][0][0];
        ImageGUI gui = new ImageGUI();
        gui.setVisible(true);
    }

    public static ImageIcon openImage(String filepath){
        try{

        File f = new File(filepath);
        BufferedImage image = ImageIO.read(f);
        originalImageBuffer = image;
        ImageIcon icon = new ImageIcon(image);
        return icon;

        }
        catch(Exception e){
            e.printStackTrace();
            return new ImageIcon();
        }

    }
}

import java.awt.Dimension;
import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;
import javax.swing.ImageIcon;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JPanel;
import javax.swing.UIManager;

public class ImageGUI extends JFrame implements ActionListener{

    private JFrame window;

    private JMenuItem mOpenFile;
    private JMenuItem mSaveFile;
    private JMenuItem mExitCommand;

    private JMenuBar parentBar;
    private JMenu fileMenu;
    private JMenu commandMenu;

    private JPanel mainPanel;

    public ImageIcon img;

    private JLabel mLabel;

    public ImageGUI(){
        super();
        try{
        UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
        }
        catch(Exception e){
            e.printStackTrace();
        }
        //setup CommandMenu
        commandMenu = makeMenu("Command", 'C');

        //setup FileMenu
        fileMenu  = makeMenu("File", 'F');
        mOpenFile     = makeMenuItem(fileMenu, "Open...", 'O');
        mSaveFile     = makeMenuItem(fileMenu, "Save...", 'S');
        mExitCommand  = makeMenuItem(fileMenu, "Exit", 'X');

        //setup parentBar
        parentBar = new JMenuBar();
        parentBar.add(fileMenu);
        parentBar.add(commandMenu);

        //main panel
        mainPanel = new JPanel(new BorderLayout());
        mLabel = new JLabel();
        mainPanel.add(mLabel, BorderLayout.CENTER);
        setJMenuBar(parentBar);
        setSize(new Dimension(400, 300));

    }

    protected JMenuItem makeMenuItem(JMenu menu, String name, char mnemonic){
        JMenuItem m = new JMenuItem(name, (int) mnemonic);
        m.addActionListener(this);
        menu.add(m);
        return m;
    }

    protected JMenu makeMenu(String name, char mnemonic){
        JMenu menu = new JMenu(name);
        menu.setMnemonic(mnemonic);
        return menu;
    }


    @Override
    public void actionPerformed(ActionEvent arg0) {
        if(arg0.getSource()==mOpenFile){
            String path = null;

            JFileChooser jfc = new JFileChooser();
            jfc.setCurrentDirectory(new File("."));

            int result = jfc.showOpenDialog(this);

            if (result == JFileChooser.APPROVE_OPTION) {
                File file = jfc.getSelectedFile();
                path = file.getAbsolutePath();
            }

            img=ImageEditEngine.openImage(path);
            mLabel= new JLabel(img);
            mLabel.setVisible(true);
            this.repaint();
            pack();

        }

    }
}

紧随其后的 mLabel 上的 toString() 值：

mLabel = new JLabel(img);

如下

javax.swing.JLabel[,0,0,0x0,invalid,alignmentX=0.0,alignmentY=0.0,
border=,flags=8388608,maximumSize=,minimumSize=,preferredSize=,
defaultIcon=javax.swing.ImageIcon@2bd58ce,disabledIcon=,
horizontalAlignment=CENTER,horizontalTextPosition=TRAILING,
iconTextGap=4,labelFor=,text=,verticalAlignment=CENTER,
verticalTextPosition=CENTER]

Answer 1

如果我想在 GUI 上显示图像，我将图像嵌入到 JLabel 中。它工作得很好。

BufferedImage img = ImageIO.read(new File(IMG_PATH));
ImageIcon icon = new ImageIcon(img);
JLabel label = new JLabel(icon);

Displaying an image in Java Swing

这应该有效！

Answer 2

根本问题是面板从未添加到框架中。代码还有许多其他问题，我修复了其中一些问题（通过删除整个部分），其他问题我进行了调整。下面显示的代码还有其他问题需要修复（其中一两个是我在惰性编码中引入的 - 但它们不是致命的）。

话虽如此，这段代码现在可以使用了。仔细查看它以获取提示。注意是热链接到图片的MCVE，所以应该很容易测试。

import java.awt.image.*;
import java.awt.*;
import javax.swing.*;
import javax.imageio.*;
import java.net.URL;

public class ImageEditEngine {

    private static int[][][] originalImage;
    private static BufferedImage originalImageBuffer;

    public ImageEditEngine() {
        originalImage = new int[0][0][0];
        ImageGUI gui = new ImageGUI();
        gui.setVisible(true);
    }

    public static ImageIcon openImage(){
        try{
            URL url = new URL("https://i.stack.imgur.com/OVOg3.jpg");

            BufferedImage image = ImageIO.read(url);
            originalImageBuffer = image;
            ImageIcon icon = new ImageIcon(image);
            return icon;

        }
        catch(Exception e){
            e.printStackTrace();
            return new ImageIcon();
        }
    }

    public static void main(String[] args) {
        new ImageEditEngine();
    }
}


class ImageGUI extends JFrame {

    private JPanel mainPanel;

    public ImageIcon img;

    private JLabel mLabel;

    public ImageGUI(){
        super();
        setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        try{
            UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
        }
        catch(Exception e){
            e.printStackTrace();
        }
        //main panel
        mainPanel = new JPanel(new BorderLayout());
        mLabel = new JLabel();
        mainPanel.add(mLabel, BorderLayout.CENTER);

        add(mainPanel);

        setSize(new Dimension(400, 300));

        img=ImageEditEngine.openImage();
        mLabel.setIcon(img);
        mLabel.setVisible(true);
        this.repaint();
        pack();
    }
}

在 Java 中使用 Swing 显示图像

Displaying an Image using Swing in Java

java

image

swing

jfilechooser