java - 我的 swing 应用程序中的边框布局出了什么问题？

Question

我有一个简单的应用程序，我想在可滚动面板中显示大图像。我正在使用来自 http://today.java.net/pub/a/today/2007/03/27/navigable-image-panel.html 的 NavigableImagePanel

首先是我得到的结果 -

图像目前是顶部按钮附近的一个非常小的面板。这是 BorderLayout.CENTER

NavigableImagePanel 的代码:

http://pastebin.com/1wHRwMJU

和我的 OpenImage.java 代码:

import java.awt.*;
import java.awt.event.*;

import javax.imageio.ImageIO;
import javax.swing.*;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;


public class OpenImage extends JFrame implements ActionListener{
/**
 * 
 */
private static final long serialVersionUID = 9066218264791891436L;
Image img;

public OpenImage() throws IOException{
    super("Resize and Rotate");

    setDefaultCloseOperation(EXIT_ON_CLOSE);
    BorderLayout grid = new BorderLayout(); 

    //this.setLayout(grid);
    setSize(900,700);
    setVisible(true);   


    //Row 1 holds some important buttons 
    //FlowLayout layout1 = new FlowLayout();
    //MigLayout mig = new MigLayout();
    JPanel row1 = new JPanel();
    //LayoutManager grid = new BoxLayout(row1, BoxLayout.X_AXIS);
    //row1.setLayout(grid);
    //row1.setLayout(BorderLayout.NORTH);
    //row1.setMaximumSize(new Dimension(100,100));
    BorderLayout border = new BorderLayout();
    //row1.setPreferredSize(new Dimension(0, 400));

    JButton open = new JButton ("Open");
    open.addActionListener(this);
    JButton rotate = new JButton("Rotate");
    rotate.addActionListener(this);
    JButton resize = new JButton("Resize");
    resize.addActionListener(this);
    JButton exit = new JButton ("Exit"); 
    exit.addActionListener(this);
    row1.add(open);
    row1.add(rotate);
    row1.add(resize);
    row1.add(exit);




    //This section has a workable picture panel, but it is too large. 
    //ImagePanel imagepanel = new ImagePanel();
    BorderLayout grid1 = new BorderLayout();
    Container cp = getContentPane();
    cp.setLayout(grid1);

    //add(row1);

    //JScrollPane row2 = new JScrollPane(imagepanel, JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);


    BufferedImage img = ImageIO.read(new File("/home/adam/snow.jpg"));

    NavigableImagePanel imagepanel = new NavigableImagePanel(img);

    JPanel row2 = new JPanel();
    row2.add(imagepanel);
    //row2.repaint();
    JButton save = new JButton("Save");
    JPanel row3 = new JPanel();
    row3.add(save);

    cp.add(BorderLayout.NORTH, row1);
    cp.add(BorderLayout.CENTER, row2);
    cp.add(BorderLayout.SOUTH, row3);


}




public void actionPerformed(ActionEvent e) {
    String command = e.getActionCommand();
    if (command == "Exit"){
        System.exit(0);
    }
    if (command == "Open"){
        JFileChooser chooser = new JFileChooser();
        int returnVal = chooser.showOpenDialog(this);


    }
}



//This method below is now being deprecat


public static void main(String [] args){
    try {
        //UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
        UIManager.setLookAndFeel("javax.swing.plaf.metal.MetalLookAndFeel");
    } catch (UnsupportedLookAndFeelException ex) {
        ex.printStackTrace();
    } catch (IllegalAccessException ex) {
        ex.printStackTrace();
    } catch (InstantiationException ex) {
        ex.printStackTrace();
    } catch (ClassNotFoundException ex) {
        ex.printStackTrace();
    }
    UIManager.put("swing.boldMetal", Boolean.FALSE);
    try {
        JFrame frame = new OpenImage();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

Answer 1

1. 您在此处发布的代码缺少大量 Java 导入，在这里看不到任何来自 Swing 包的 Java 导入，以及为 Image 导入。
2. setVisible(true); 必须是构造函数中的最后一行代码。
3. 在任何情况下，setBackground() 都可以帮助您发现任何问题。
4. 在所有情况下尝试使用 pack() 而不是 setSize(900,700);
5. 因为我设置了 imagepanel.setPreferredSize(new Dimension(600, 400));，所以 JComponents 必须返回首选大小是错误的，然后 pack( ) 将正常工作。
6. 不知道你从哪里得到这段代码，所以几乎不可能无异常(exception)地工作。
7. 只是清理无用的烂摊子

来自代码

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Image;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
import javax.swing.border.LineBorder;

public class OpenImage extends JFrame implements ActionListener {

    private static final long serialVersionUID = 9066218264791891436L;
    private Image img;

    public OpenImage() {
        super("Resize and Rotate");

        JButton open = new JButton("Open");
        open.addActionListener(this);
        JButton rotate = new JButton("Rotate");
        rotate.addActionListener(this);
        JButton resize = new JButton("Resize");
        resize.addActionListener(this);
        JButton exit = new JButton("Exit");
        exit.addActionListener(this);

        JPanel row1 = new JPanel();
        row1.setBackground(Color.red);
        row1.setLayout(new FlowLayout());
        row1.setBorder(new LineBorder(Color.black, 1));
        row1.add(open);
        row1.add(rotate);
        row1.add(resize);
        row1.add(exit);

        JPanel imagepanel = new JPanel();
        imagepanel.setLayout(new BorderLayout());
        imagepanel.setBackground(Color.blue);
        imagepanel.setBorder(new LineBorder(Color.black, 1));
        imagepanel.setPreferredSize(new Dimension(600, 400));

        JPanel row2 = new JPanel();
        row2.setLayout(new BorderLayout(10, 10));
        row2.setBorder(new LineBorder(Color.black, 1));
        row2.add(imagepanel, BorderLayout.CENTER);
        row2.setBackground(Color.red);
        JButton save = new JButton("Save");

        JPanel row3 = new JPanel();
        row3.setBorder(new LineBorder(Color.black, 1));
        row3.setBackground(Color.green);
        row3.setLayout(new FlowLayout());
        row3.add(save);

        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setLayout(new BorderLayout(10, 10));
        add(BorderLayout.NORTH, row1);
        add(BorderLayout.CENTER, row2);
        add(BorderLayout.SOUTH, row3);
        pack();
        setVisible(true);
    }

    public void actionPerformed(ActionEvent e) {
        String command = e.getActionCommand();
        if (command == "Exit") {
            System.exit(0);
        }
        if (command == "Open") {
            JFileChooser chooser = new JFileChooser();
            int returnVal = chooser.showOpenDialog(this);
        }
    }

    public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                OpenImage openImage = new OpenImage();
            }
        });
    }
}