Question

我正在构建一个程序，显示给定位置的温度（参见屏幕截图）我想在displayPanal（JPanal）中显示结果。我将paint组件放在displayPanel的扩展类中。但它没有显示任何东西。我只是尝试使用g.drawString方法显示“Hello”来测试，但它没有显示任何内容。所以我被迫继续前进。

    public static void main(String[] args) {

    SwingUtilities.invokeLater(new Runnable() {
        public void run() {
            createAndShowGUI(); 
        }
    });
}//main

private static void createAndShowGUI(){
    GridLayout panelLayout = new GridLayout(3,0);
    panelLayout.setHgap(10);
    panelLayout.setVgap(10);
    final JPanel panel = new JPanel(panelLayout);

    //location label
    JLabel locationLabel = new JLabel("Location");
    panel.add(locationLabel);
    //text Field for location
    final JTextField locationText = new JTextField();
    panel.add(locationText);
    //month label
    JLabel monthLabel = new JLabel("Month of the Year");
    panel.add(monthLabel);
    //comboBox for months
    String[] months = new String[] {"","January", "February", "March", "April", "May", "June",
            "July", "August", "September", "October", "November", "December"};
    JComboBox<String> monthList = new JComboBox<>(months);
    panel.add(monthList);
    //JCheckBox
    JCheckBox celsiusCheck = new JCheckBox("Show Celsius Temperature");
    panel.add(celsiusCheck);

    //Button inside button pane
    JPanel buttonPane = new JPanel();
    buttonPane.setLayout(new BoxLayout(buttonPane, BoxLayout.LINE_AXIS));
    buttonPane.setBorder(BorderFactory.createEmptyBorder(0, 150, 0, 0));
    JButton goButton = new JButton("Go");
    buttonPane.add(goButton);

    //JPanel for display
    JPanel displayPanel = new JPanel();
    displayPanel.setBorder(BorderFactory.createLineBorder(Color.black));


    //Create and setup window
    JFrame frame = new JFrame("Midterm Project");
    frame.setSize(500, 600);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    JPanel mainPanel = new JPanel(new GridLayout(3, 1));
    mainPanel.add( panel );
    mainPanel.add( buttonPane );
    mainPanel.add( displayPanel );

    //Set up the content pane.
    mainPanel.setOpaque(true); //content panes must be opaque
    frame.setContentPane(mainPanel);

    //Display the window.
    frame.pack();
    frame.setVisible(true);


}//createAndShowGUI()

class displayPanel extends JPanel {
    double fahrenheit = generateRand();
    //double celsius = getCelsius(fahrenheit);
    String celsius = Double.toString(getCelsius(fahrenheit));
    @Override
    public void paintComponent(Graphics g) {
        g.drawString("Hello", 10, 10);
    }//paintComponent(); 
}

Answer 1

.box {
    display: table;
    margin-right: auto; 
    margin-left: auto; 
    width: 100%;
}

.rec {
    display: table-cell;
    padding: 10px;
    text-align: center;
    background: red;
}

.navigation {
    display: table-cell;
    background: yellow;
}

.nagivation.next > a {
    vertical-align: right;  
}

应该......

  JPanel displayPanel = new JPanel();

从它的外观来看！

displayPanel被更改为displayPanelVar，因为变量名不能与类相同，可能值得将displayPanel类名重命名为DisplayPanel

paintComponent不显示任何内容

1 个答案: