Question

我想要做的是将图像加载到JScrollPane中，由其他组件包围，当窗口小于图像时，它应该被滚动条包围，以便您可以通过滚动来查看整个图像。 / p>

我这样做是通过使用我自己的类ImagePanel构建一个JScrollPane，它扩展了绘制图像的JPanel。图像被正确加载和显示，但滚动条消失。是否有一些JComponents我误解或出了什么问题？

public class ImagePanel extends JPanel {
    private BufferedImage img;
    public ImagePanel () {

    }
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.drawImage(img, 0, 0, this);
    }
    public void setImage(BufferedImage img) {
        this.img = img;
    }
}


public class MainGUI extends JPanel {
    private ImagePanel imgP;
    private JScrollPane pane;
    public MainGUI () {
        setLayout(new GridBagLayout());

        //Create local components
        //JComponents
        JButton hideButton = new JButton("Hide");
        JButton hidecategoryButton = new JButton ("Hide Category");
        JButton removeButton = new JButton("Remove");
        JButton searchButton = new JButton("Search");
        JButton whatishereButton = new JButton("What is here?");

        JComboBox<String> placeComboBox;

        JLabel categoriesLabel = new JLabel("Categories");
        JLabel newLabel = new JLabel("New: ");

        JTextArea categoriesArea = new JTextArea();

        JTextField searchField = new JTextField(10);

        //Other
        String[] placeTypes = {"Named Place", "Described Place"};


        //Initialize and add behaviour
        searchButton.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                String s = searchField.getText();

            }

        });
        categoriesArea.setEditable(false);
        placeComboBox = new JComboBox<>(placeTypes);

        searchField.setToolTipText("Search...");
        searchField.setMinimumSize(new Dimension(5, 1));

        //Just fileloading test
        BufferedImage bi2 = null;
        try {
            bi2 = ImageIO.read(new File("dafoe.jpg"));
        }
        catch (Exception ex) {

        }
        imgP = new ImagePanel();
        imgP.setImage(bi2);
        pane = new JScrollPane(imgP);

        //Add to panel
        GridBagConstraints gc;

        //Top row
        JPanel toprowPanel = new JPanel();
        toprowPanel.add(newLabel);
        toprowPanel.add(placeComboBox);
        toprowPanel.add(searchField);
        toprowPanel.add(searchButton);
        toprowPanel.add(hideButton);
        toprowPanel.add(removeButton);
        toprowPanel.add(whatishereButton);

        gc = new GridBagConstraints();
        gc.gridx = 0;
        gc.gridy = 0;
        gc.weightx = 1;
        //gc.gridwidth = 6;
        add(toprowPanel, gc);

        //Hide category
        gc = new GridBagConstraints();
        gc.anchor = GridBagConstraints.NORTH; 
        gc.gridx = 7;
        gc.gridy = 3;
        gc.weightx = 0;
        gc.weighty = 0;
        add(hidecategoryButton, gc);

        //Category Label
        gc = new GridBagConstraints();
        gc.anchor = GridBagConstraints.BELOW_BASELINE;
        gc.gridx = 7;
        gc.gridy = 1;
        gc.weightx = 0;
        gc.weighty = 0;
        add(categoriesLabel, gc);       


        //categoriesarea
        gc = new GridBagConstraints();
        gc.anchor = GridBagConstraints.BASELINE_TRAILING;
        gc.fill = GridBagConstraints.BOTH;
        gc.gridx = 7;
        gc.gridy = 2;
        gc.ipadx = 5;
        gc.ipady = 70;
        gc.weightx = 0;
        gc.weighty = 0;
        add(categoriesArea, gc);

        //Image
        gc = getImageConstraints();

        add(pane,  gc);
    }

    public void updateImage(BufferedImage bi) {
        imgP.setImage(bi);
        //imgP.repaint();

        pane.repaint();
    }
    private GridBagConstraints getImageConstraints() {
        GridBagConstraints gc = new GridBagConstraints();
        gc.fill = GridBagConstraints.BOTH;
        gc.gridheight = 3;
        gc.gridwidth = 1;
        gc.gridx = 0;
        gc.gridy = 1;
        gc.weightx = 1;
        gc.weighty = 1;
        return gc;
    }
}

Answer 1

我自己的类ImagePanel，它扩展了绘制图像的JPanel。图像被正确加载和显示，但滚动条消失。

当添加到滚动窗格的组件的首选大小大于滚动窗格的大小时，滚动条将自动出现。

您的自定义组件的首选大小为（0,0），因此滚动条将永远不会出现。

您需要覆盖ImagePanel类的getPreferredSize()以返回图像的大小。

或者更简单地使用带有ImageIcon的JLabel并将标签添加到滚动窗格。 JLabel已正确实现getPreferredSize()方法。

Answer 2

当布局为GridBagLayout时，您无法使用滚动条。您必须使用BorderLayout或FlowLayout

使用jtable链接示例（类似于图像）：

http://myquestionjava.blogspot.com/2016/04/jscrollbars-and-jtable-in-java.html

使用JPanel构建JScrollPane时，滚动条会消失

2 个答案: