java - 使用数据库创建 jcomponents

Question

我想使用数据库动态创建 jcomponents。当我打开任何 jframe 或 jpanel 组件时，如 jlabel、jtextfields、jcombobox 等应该通过读取数据库行来创建。我对如何从数据库值(即 String 中的 jcomponent 对象)提供引用感到困惑。这是我的数据库表

    try{
        con = DriverManager.getConnection("jdbc:mysql://localhost:3306/db","root","pass");
        stat = con.createStatement();
        ResultSet rs = stat.executeQuery("select * from design");
        while(rs.next()){
            jTextField1 = new JTextField();
            jTextField1.setSize(rs.getInt("height"),rs.getInt("width"));
            jTextField1.setLocation(rs.getInt("x"), rs.getInt("y"));
        }
        rs.close();
        stat.close();
        con.close();
    }
    catch(Exception e){
        System.out.println(e);
    }

这是演示表。我知道这行不通，因为我无法与对象和数据库通信。我想在 jframe 上打印 jcomponents。我将编写 for 循环以多次打印它们。请帮助我。

Answer 1

首先请看@AndrewThompson 的明智建议:

Java GUIs might have to work on a number of platforms, on different screen resolutions & using different PLAFs. As such they are not conducive to exact placement of components. To organize the components for a robust GUI, instead use layout managers, or combinations of them, along with layout padding & borders for white space.

有一些有助于理解其含义的主题:

• Non resizable window border and positioning
• Should I avoid the use of set(Preferred|Maximum|Minimum)Size methods in Java Swing?
• Nested Layout Example
• Providing white space in a Swing GUI

您会看到极力反对使用 setLocation()、setBounds() 或 setSize() 等方法。但是，我在应用允许自定义表单之前已经看到了这种方法。但是您可以存储 GridBagLayout 的约束，而不是特定的 (x,y) 坐标和固定的 (width,height) .假设您有一个这样的表:

我首先使用一个类来包装来自数据库的数据:

public class Data {
    private String componentType, text;
    private int column, row, width, height, weightX, weightY;

    public Data(String componentType, int column, int row, int width, int height
                ,int weightX, int weightY, String text) {

        this.componentType = componentType;
        this.column = column;
        this.row = row;
        this.width = width;
        this.height = height;
        this.weightX = weightX;
        this.weightY = weightY;
        this.text = text;
   }

   // getters and setters here
}

由于数据库调用是一项耗时的任务，您必须考虑使用 SwingWorker在后台线程中执行数据库调用(耗时任务)并在 Event Dispatch Thread 中创建/更新您的 GUI .

说到这里你可能会有这样的事情:

public class Demo {

    private JPanel content;
    private JFrame frame;

    private void createAndShowGUI() {        
        content = new JPanel(new GridBagLayout());

        SwingWorker<Void, Data> worker = new SwingWorker<Void, Data>() {
            @Override
            protected Void doInBackground() {                    
                try{
                   Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/db","root","password");
                   Statement stat = con.createStatement();
                   ResultSet rs = stat.executeQuery("select * from TableName");
                   while(rs.next()){
                      String componentType = rs.getString("component");
                      int column = rs.getInt("x");
                      int row = rs.getInt("y");
                      int width = rs.getInt("width");
                      int height = rs.getInt("height");
                      int weightx = rs.getInt("weightx");
                      int weighty = rs.getInt("weighty");
                      String text = rs.getString("text");
                      Data data = new Data(componentType, column, row, width, height
                                          ,weightx, weighty, text);
                      publish(data);
                  }
                  rs.close();
                  stat.close();
                  con.close();
              } catch(Exception e) {
                  System.out.println(e);
              }

                return null;
            }

            @Override
            protected void process(List<Data> chunks) {
                for(Data data : chunks) {

                    JComponent component = null;
                    if(data.getComponentType().equalsIgnoreCase("JTextField")) {
                        component = new JTextField(data.getText());
                    }

                    if(data.getComponentType().equalsIgnoreCase("JComboBox")) {
                        component = new JComboBox();
                    }

                    if(data.getComponentType().equalsIgnoreCase("JLabel")) {
                        component = new JLabel(data.getText());
                    }

                    if(component != null) {
                        GridBagConstraints constraints = new GridBagConstraints();
                        constraints.gridx = data.getColumn();
                        constraints.gridy = data.getRow();
                        constraints.gridwidth = data.getWidth();
                        constraints.gridheight = data.getHeight();
                        constraints.weightx = data.getWeightX();
                        constraints.weighty = data.getWeightY();

                        constraints.anchor = GridBagConstraints.WEST;
                        constraints.fill = GridBagConstraints.BOTH;
                        constraints.insets = new Insets(8,8,8,8);
                        content.add(component, constraints);
                    }

                }
            }

            @Override
            protected void done() {
                frame = new JFrame("Demo");
                frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
                frame.getContentPane().add(content);
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        };

        worker.execute();
    }


    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new Demo().createAndShowGUI();
            }
        });
    }
}

你会看到这样的东西: