Question

我有一个名为＆＃39; Panel＆＃39;它扩展了JPanel，它位于另一个名为＆＃39; Main＆＃39;的类中。构造函数实例化JFrame和所有GUI组件，并将其全部设置，例如大小。

班级＆＃39;小组＆＃39;扩展JPanel有一个方法public void paintComponent（Graphics g）{}，在里面我添加了一些JButtons并使用了g.drawString＆＃39; s。

然后在＆＃39; Main＆＃39;上课时，我添加了＆＃39; Panel＆＃39;到JFrame。

我的问题是，我正在尝试将一个actionListener实现到一个添加到＆＃39; Panel＆＃39;类。 actionListener函数会添加更多按钮并使用g.drawString。现在我在哪里放置ActionListener才能这样做？如何将g.drawString用于特定面板，而g.drawString行位于另一个类中，即ActionListener类？我需要在actionPerformed中使用paintg of paintComponent。

谢谢！

编辑 - 代码示例：

public class Main{

private JFrame jf;
private JTextField jtf1;
private JTextField jtf2;    
private Panel p;    
private JComboBox jcb1;
private JComboBox jcb2;     
private JButton button;     
private Object options[];

//ActionListener Variables
private int string1 = 150;
private int string2 = 150;      
private int yJtf1 = 150;
private int yJtf2 = 160;        
private int cb1 = 140;
private int cb2 = 165;      
private int count = 0;

    public Main(){

        jf= new JFrame();
        jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        jf.setSize(700, 700);

        p = new Panel();

        jtf1 = new JTextField("", 20);
        jtf2= new JTextField("", 20);

        Object options[] = {""};

        jcb1 = new JComboBox(tools);
        jcb2 = new JComboBox(tools);

        button = new JButton("+");

        jf.add(p);
        jf.setVisible(true);`
    }

    public class Panel extends JPanel{

        public Panel(){
            this.setLayout(null);
        }

        public void paintComponent(Graphics g){

            super.paintComponent(g);

            /*button.addActionListener(new ActionListener(){  //Would this work or should the ActionListener be a class as shown below?
                public void actionPerformed(ActionEvent e){

                    if(count < 3){ //Won't be allowed to add anymore after 3 times
                        string1 += 50;
                        string2 += 50;

                        jtf1 += 50;
                        jtf2 += 50;

                        cb1 += 50;
                        cb2 += 45;

                        //Would like to add the following components to the 'Panel' (which is a JPanel) whenever the JButton 'button' already added to 'Panel' is clicked.
                        p.add(jtf1); //Would doing p.add really add to the panel when the ActionListener is called?
                        jtf1.setBounds(60, yJtf1, 50, 40);
                        p.add(jtf2);
                        jtf2.setBounds(60, yJtf2, 50, 40);

                        add(jcb1);
                        jcb1.setBounds(250, cb1, 50, 40);
                        add(left2);
                        jcb2.setBounds(250, cb2, 50, 40);

                        Font font = new Font("TimesRoman", Font.BOLD, 18);
                        g.setFont(font);  //Getting error on 'g' regardless

                        g.drawString("Hi", 15, string1); //This is the main problem, how would I be able to add this strings to the 'Panel' (which is a JPanel)
                        g.drawString("There", 330, string1);
                    }
                    count++;
                }
            });*/

            add(jtf1);
            jtf1.setBounds(100, 30, 120, 30);
            add(jtf2);
            ljtf2.setBounds(100, 60, 120, 30);

            add(button);
            plusButton.setBounds(200,150, 50, 50);
            //button.addActionListener(new ButtonClicked()); if doing ActionListener via class like below

            add(jcb1);
            jcb1.setBounds(300, 350, 100, 50);
            add(ljcb2);
            jcb2.setBounds(300, 350, 100, 25);

            Font font = new Font("Arial", Font.BOLD, 12);
            g.setFont(font);
            g.drawString("Item:", 40, 45);
            g.drawString("Cost:", 40, 75);
        }
    }


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

    class ButtonClicked implements ActionListener{ //Action Listener: The follow is what I am trying to implement
        public void actionPerformed(ActionEvent ae){
            if(count < 3){ //Won't be allowed to add anymore after 3 times
                string1 += 50;
                string2 += 50;

                jtf1 += 50;
                jtf2 += 50;

                cb1 += 50;
                cb2 += 45;

                //Would like to add the following components to the 'Panel' (which is a JPanel) whenever the JButton 'button' already added to 'Panel' is clicked.
                p.add(jtf1); //Would doing p.add really add to the panel when the ActionListener is called?
                jtf1.setBounds(60, yJtf1, 50, 40);
                p.add(jtf2);
                jtf2.setBounds(60, yJtf2, 50, 40);

                mp.add(jcb1);
                jcb1.setBounds(250, cb1, 50, 40);
                mp.add(left2);
                jcb2.setBounds(250, cb2, 50, 40);

                Font font = new Font("TimesRoman", Font.BOLD, 18);
                g.setFont(font); 

                g.drawString("Hi", 15, string1); //This is the main problem, how would I be able to add this strings to the 'Panel' (which is a JPanel)
                g.drawString("There", 330, string1);
            }
            count++;
        }
    }
}

Answer 1

我需要在actionPerformed中使用paintG of paintComponent。＆＃34;`

不，你不会因为Swing图形被动不活跃。 Graphics对象将驻留在JPanel的paintComponent方法中，当它只调用paintComponent方法时，它将从JVM传递给它。然后，actionPerformed方法将更改String变量的值，或者更改ArrayList<String>，调用repaint()，然后JPanel的paintComponent方法将使用更改的String来绘制相应的文本。 / p>

如果您需要更具体的帮助，请考虑告诉我们更多详情并发布minimal example program。

修改
在审核您的代码时，我有几点建议：

请尝试稍微修改您的代码，以使其可编辑或尽可能接近可编译。

除了在paintComopnent(...)方法内部绘画外，不要添加组件或做任何事情。您无法完全控制何时或甚至是否会调用该方法，并且在此方法中放置一些内容会导致不必要的副作用，例如仅仅无法工作的组合框。

如果您希望程序中显示文字，则可以随时添加JLabel。

您的程序使用空布局和setBounds(...)导致严格的GUI在某个系统上看起来不错，但在任何其他系统或屏幕分辨率上看起来都很差。此外，以这种方式创建的程序非常难以调试，维护和升级。而是使用布局管理器，因为这是他们擅长的：创建可以轻松增强和更改的复杂灵活的GUI。

修改
我猜你真正想做什么，可能是添加更多组件以允许用户在GUI中输入更多数据。您还希望添加文本，以引导用户了解组件的用途。如果是这样，那么最好的解决方案是不要在paintComponent中将字符串添加到GUI，而是以有组织的方式添加字符串/组件，其中字符串显示在JLabel中，组件和标签都保存在JPanel中或JPanels，并使用布局管理器添加到GUI。

例如，如果您希望用户在两个JTextfields中添加数据并拥有两个JComboBox，然后允许用户在需要时再添加3个这样的人，GUI可能看起来像这样：

import java.awt.BorderLayout; import java.awt.Dimension; import java.awt.GridBagConstraints; import java.awt.GridBagLayout; import java.awt.GridLayout; import java.awt.Insets; import java.awt.Window; import java.awt.event.ActionEvent; import java.awt.event.KeyEvent; import java.util.ArrayList; import java.util.List; import javax.swing.*; @SuppressWarnings("serial") public class Main2 extends JPanel { private List<DataPanel> dataPanelList = new ArrayList<>(); private JPanel dataPanelHolder = new JPanel(); public Main2() { DataPanel dataPanel = new DataPanel(); dataPanelList.add(dataPanel); setLayout(new BorderLayout()); dataPanelHolder.setLayout(new BoxLayout(dataPanelHolder, BoxLayout.PAGE_AXIS)); dataPanelHolder.add(dataPanel); JPanel innerBorderLayoutPanel = new JPanel(new BorderLayout()); innerBorderLayoutPanel.add(dataPanelHolder, BorderLayout.PAGE_START); JScrollPane scrollPane = new JScrollPane(innerBorderLayoutPanel); scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS); int w = dataPanel.getPreferredSize().width; int h = dataPanel.getPreferredSize().height * 4; Dimension viewPortSize = new Dimension(w, h); scrollPane.getViewport().setPreferredSize(viewPortSize); JPanel buttonPanel = new JPanel(new GridLayout(1, 0, 5, 0)); buttonPanel.add(new JButton(new AddDatatAction("Add"))); buttonPanel.add(new JButton(new ExitAction("Exit", KeyEvent.VK_X))); add(scrollPane, BorderLayout.CENTER); add(buttonPanel, BorderLayout.PAGE_END); } private class AddDatatAction extends AbstractAction { private int maxCount = 4; public AddDatatAction(String name) { super(name); int mnemonic = (int)name.charAt(0); putValue(MNEMONIC_KEY, mnemonic); } @Override public void actionPerformed(ActionEvent e) { if (dataPanelList.size() < maxCount) { DataPanel dataPanel = new DataPanel(); dataPanelList.add(dataPanel); dataPanelHolder.add(dataPanel); dataPanelHolder.revalidate(); dataPanelHolder.repaint(); } } } private class ExitAction extends AbstractAction { public ExitAction(String name, int mnemonic) { super(name); putValue(MNEMONIC_KEY, mnemonic); } @Override public void actionPerformed(ActionEvent e) { Window win = SwingUtilities.getWindowAncestor(Main2.this); win.dispose(); } } private static void createAndShowGui() { JFrame frame = new JFrame("Main2"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.getContentPane().add(new Main2()); frame.pack(); frame.setLocationRelativeTo(null); frame.setVisible(true); } public static void main(String[] args) { SwingUtilities.invokeLater(new Runnable() { public void run() { createAndShowGui(); } }); } } @SuppressWarnings("serial") class DataPanel extends JPanel { private static final String[] TOOLS = {"Tool 1", "Tool 2", "Tool 3", "Tool 4"}; private static final String[] FIELD_LABELS = {"Item", "Cost"}; private static final String[] COMBO_LABELS = {"Foo", "Bar"}; private JTextField[] fields = new JTextField[FIELD_LABELS.length]; private List<JComboBox<String>> comboList = new ArrayList<>(); public DataPanel() { setBorder(BorderFactory.createTitledBorder("Data")); setLayout(new GridBagLayout()); for (int i = 0; i < FIELD_LABELS.length; i++) { add(new JLabel(FIELD_LABELS[i]), createGbc(0, i)); fields[i] = new JTextField(10); add(fields[i], createGbc(1, i)); JComboBox<String> combo = new JComboBox<>(TOOLS); comboList.add(combo); add(combo, createGbc(2, i)); add(new JLabel(COMBO_LABELS[i]), createGbc(3, i)); } } public static GridBagConstraints createGbc(int x, int y) { GridBagConstraints gbc = new GridBagConstraints(); gbc.gridx = x; gbc.gridy = y; gbc.gridwidth = 1; gbc.gridheight = 1; gbc.weightx = 1.0; gbc.weighty = 1.0; int ins = 4; gbc.insets = new Insets(ins, ins, ins, ins); return gbc; } }

可能看起来像：

添加了一个数据通道
四，补充说：

如何在另一个类中的JPanel类中实现ActionListener？

1 个答案: