Java Swing : JScrollPane dosen't expand to fit JPanel in it

Question

我有一个JTabel我想将其添加到 JScrollPane 。但是JScrollPane尺寸非常小。我尝试将表设置为 JPanel (已调整大小)然后输入JPanel至JScrollPane但它不起作用。

这是我的代码:

 static public class PnGiaoDich extends JPanel{
    public PnGiaoDich(){
        //size & background
        setPreferredSize( new Dimension(1050, 435));
        setBackground(new Color(255,255,255));

        //layout
        setLayout(new GridBagLayout());
        GridBagConstraints c = new GridBagConstraints(); 

        //create table
        String[] columnNames = {"Ngày giao dịch",
                    "Loại gio dịch | Mô tả",
                    "Tình trạng",
                    "Số tiền"
                    };

        Object[][] data = {
                        {"","","",""},
                        {"","","",""},
                        {"","","",""},
                        {"","","",""}
                        };

        JTable table = new JTable(data,columnNames);
        TableColumn column = null;
        table.getColumnModel().getColumn(0).setPreferredWidth(150);
        table.getColumnModel().getColumn(1).setPreferredWidth(525);
        table.getColumnModel().getColumn(2).setPreferredWidth(150);
        table.getColumnModel().getColumn(3).setPreferredWidth(150);

        // create table to put into JScrollPane
        JPanel pnTable = new JPanel();
        pnTable.setBorder(BorderFactory.createLineBorder(Color.red));
        pnTable.setPreferredSize(new Dimension(800, 600));
        pnTable.add(table);
        //Add panel to JScrollPane
        JScrollPane scrollpn = new JScrollPane(pnTable);
        //table.setFillsViewportHeight(true); 

        c.gridx = 0;
        c.gridy = 1;
        c.gridwidth = 2;
        c.insets = new Insets(20,20,20,20);
        c.weightx = 1;
        c.weighty = 1;
        c.anchor = GridBagConstraints.NORTH;
        add(scrollpn,c);

       //
    }
}

但是如果我将这些代码发布到主 JFrame，它就可以正常工作。

这是我的完整代码:enter link description here

我的 JScrollPane 的图像:

Answer 1

好吧，让我们来看看......

setPreferredSize( new Dimension(1050, 435));

...尽量避免这样做。如果您“必须”这样做，请重写 getPreferredSize，因为 setPreferredSize 是您的“稳定”UI 的一个漏洞

setBackground(new Color(255,255,255));

//layout
setLayout(new GridBagLayout());
GridBagConstraints c = new GridBagConstraints(); 

//create table
String[] columnNames = {"Ngày giao dịch",
            "Loại gio dịch | Mô tả",
            "Tình trạng",
            "Số tiền"
            };

Object[][] data = {
                {"","","",""},
                {"","","",""},
                {"","","",""},
                {"","","",""}
                };

JTable table = new JTable(data,columnNames);
TableColumn column = null;
table.getColumnModel().getColumn(0).setPreferredWidth(150);
table.getColumnModel().getColumn(1).setPreferredWidth(525);
table.getColumnModel().getColumn(2).setPreferredWidth(150);
table.getColumnModel().getColumn(3).setPreferredWidth(150);

好吧，到目前为止还不错......

// create table to put into JScrollPane
JPanel pnTable = new JPanel();
pnTable.setBorder(BorderFactory.createLineBorder(Color.red));
pnTable.setPreferredSize(new Dimension(800, 600));
pnTable.add(table);
//Add panel to JScrollPane
JScrollPane scrollpn = new JScrollPane(pnTable);
//table.setFillsViewportHeight(true); 

然后...什么？为什么将 JTable 添加到使用 FlowLayout 的 JPanel，然后再添加 JScrollPane？为什么不直接将 JTable 添加到 JScrollPane 本身呢？

此外，这样做时，您还需要利用 JTable 和 JScrollPane 相互通信并确定何时进行滚动的能力。

c.gridx = 0;
c.gridy = 1;
c.gridwidth = 2;
c.insets = new Insets(20,20,20,20);
c.weightx = 1;
c.weighty = 1;
c.anchor = GridBagConstraints.NORTH;
add(scrollpn,c);

c.gridwidth = 2;？虽然它可能不会产生效果，但它引发了更多关于为什么的问题？

解决方案...

好吧，在考虑了约束并删除了额外的 JPanel 之后，问题归结为

setPreferredSize( new Dimension(1050, 435));

并且可能没有帮助 pnTable.setPreferredSize(new Dimension(800, 600));

我基本上将代码剥离回以下内容，“基本上”有效......

static public class PnGiaoDich extends JPanel {

    public PnGiaoDich() {
        setBackground(Color.WHITE);

        //layout
        setLayout(new GridBagLayout());
        GridBagConstraints c = new GridBagConstraints();

        //create table
        String[] columnNames = {"Ngày giao dịch",
            "Loại gio dịch | Mô tả",
            "Tình trạng",
            "Số tiền"
        };

        Object[][] data = {
            {"", "", "", ""},
            {"", "", "", ""},
            {"", "", "", ""},
            {"", "", "", ""}
        };

        JTable table = new JTable(data, columnNames);
        table.getColumnModel().getColumn(0).setPreferredWidth(150);
        table.getColumnModel().getColumn(1).setPreferredWidth(525);
        table.getColumnModel().getColumn(2).setPreferredWidth(150);
        table.getColumnModel().getColumn(3).setPreferredWidth(150);

        //Add panel to JScrollPane
        table.setBorder(BorderFactory.createLineBorder(Color.RED));
        JScrollPane scrollpn = new JScrollPane(table);
        //table.setFillsViewportHeight(true); 

        c.gridx = 0;
        c.gridy = 1;
        c.insets = new Insets(20, 20, 20, 20);
        c.weightx = 1;
        c.weighty = 1;
        c.anchor = GridBagConstraints.NORTH;
        add(scrollpn, c);
    }
}