Java JPanels 不会出现在 Linux 的 JFrame 中

Question

我正在编写一个应用程序，该应用程序查询数据库并将该信息拉到我添加到JFrame中的几个jpanel上。每隔30秒，我在JFrame中将一个可见性设置为false，另一个设置为true，以交替显示哪个。

这个应用程序在Windows中工作得很好，但是当我把它放在我的Ubuntu机器上(运行XFCE和openjdk-7-jre)时，面板没有显示。JFrame中的其他组件确实出现了，但我不确定哪里出了问题。同样，该程序在Windows上可以正常运行，但在Ubuntu上不行。

我试着把我的代码精简到可以自己编译和运行，但是我知道我的代码是一团糟。我几乎没有做过Java编程，所以我很抱歉这一切将会变得多么丑陋!我还删除了数据库的东西，因为它正在工作，因此没有必要让你们都看到。

感谢那些能给我指出正确方向的人!

package productivityDisplay;
import java.awt.Color;
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
public class Display implements ActionListener {
// Sizing constants
public boolean trimNames = false; // if true, trims to 10 characters (use
                                    // this if something is cut off)
int refreshRate = 600000; // Refresh rate for Data (milliseconds)
int margin = 2;
int labelHeight = 76;
Font defaultFont = new Font("Tahoma", Font.PLAIN, 50);
Color DodgerBlue = new Color(30, 144, 255);
Color OrangeRed = new Color(255, 69, 0);
Color DarkGreen = new Color(0, 100, 0);
// End Sizing constants
// Controls
private JLabel lblCountDown;
public int countDown;
private Timer refresh;
private JFrame frame;
private JLabel lblCurrTime;
private JPanel pnlGrind1, pnlGrind2;
private JLabel lblWeekSummary, lblRepairCredit,
        lblRepair2Count, lblCustom1, lblCustom2,
        lblQC, lblRepair, lblRepair2;
@SuppressWarnings("rawtypes")
private JComboBox cmbTeamNames;
// End Controls
// Data Variables
private int currentTeam;
// End Data Variables
public static void main(String[] args) {
    javax.swing.SwingUtilities.invokeLater(new Runnable() {
        public void run() {
            try {
                Display window = new Display(1); // Attempts to show
                                                    // the
                                                    // window
                window.frame.setVisible(true);
            } catch (Exception e) {
                e.printStackTrace();
                throw new Error("Yeah, it's broken.");
            }
        }
    });
}

public Display(int team) {
    initialize();
    cmbTeamNames.setSelectedIndex(team);
    getData();
}
/**
 * @wbp.parser.entryPoint
 */
@SuppressWarnings({ "unchecked", "rawtypes" })
private void initialize() {
    frame = new JFrame();
    frame.setVisible(true);
    frame.setExtendedState(frame.getExtendedState() | JFrame.MAXIMIZED_BOTH); // Maximize
                                                                                // Window
    int width = frame.getWidth();
    int height = frame.getHeight();
    //frame.setResizable(true); // Can't be resized
    frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
    frame.setLayout(null);
 // MASSIVE CHUNK OF LAYOUT CODE //
    String[] strTeamNames = { "", "Grinding", "Finishing" };
    cmbTeamNames = new JComboBox(strTeamNames); // Combo Box (Grinding,
                                                // finishing) 
    cmbTeamNames.setFont(new Font("Tahoma", Font.PLAIN, 40));
    cmbTeamNames.setBounds(20, 11, 297, 67);
    frame.getContentPane().add(cmbTeamNames);
    cmbTeamNames.setName("cmbTeamNames");
    cmbTeamNames.addActionListener(this);
    lblCurrTime = new JLabel("Clock");
    lblCurrTime.setFont(new Font("Tahoma", Font.PLAIN, 99));
    lblCurrTime.setBounds((width - 350), 11, 300, 100);
    frame.getContentPane().add(lblCurrTime);
    countDown = 0;
    lblCountDown = new JLabel("Next update in: "+countDown);
    lblCountDown.setFont(new Font("Tahoma", Font.PLAIN, 40));
    lblCountDown.setBounds(cmbTeamNames.getX() + cmbTeamNames.getWidth()
            + 40, 20, 400, 50);
    frame.getContentPane().add(lblCountDown);
    // Grinding Layout 2
    pnlGrind2 = new JPanel();
    pnlGrind2.setBounds(20, 89, (width - 50), height - 130);
    frame.getContentPane().add(pnlGrind2);
    pnlGrind2.setLayout(null);
    pnlGrind2.setBorder(BorderFactory.createLineBorder (Color.blue, 2));
    // Column1
    JSeparator separator = new JSeparator();
    separator.setBounds(0, (labelHeight + margin - 1), 300, 10);
    pnlGrind2.add(separator);
    // End Column1
    // Column2
    int leftSet = 450;
    JSeparator separator2 = new JSeparator();
    separator2.setBounds(leftSet, (labelHeight + margin - 1), 200, 10);
    pnlGrind2.add(separator2);
    // End Column2
    // Column3
    leftSet = 750;
    JSeparator separator3 = new JSeparator();
    separator3.setBounds(leftSet, (labelHeight + margin - 1), 200, 10);
    pnlGrind2.add(separator3);
    // End Column3
    // Bottom rows
    lblRepair2 = new JLabel("Repair Credit:");
    pnlGrind2.add(lblRepair2);
    lblRepair2.setFont(defaultFont);
    lblRepair2.setForeground(DodgerBlue);
    lblRepair2Count = new JLabel("");
    lblRepair2Count.setBounds(lblRepair2.getX() + lblRepair2.getWidth()
            + margin, lblRepair2.getY(), 515, labelHeight);
    pnlGrind2.add(lblRepair2Count);
    lblRepair2Count.setFont(defaultFont);
    lblRepair2Count.setForeground(DodgerBlue);
    // End Bottom rows
    pnlGrind2.setVisible(false);
    pnlGrind2.setBackground(new Color(0, 0, 204)); // Used to see panel
    // better
    // End Grinding Layout 2
    // Grinding Layout 1
    pnlGrind1 = new JPanel();
    pnlGrind1.setBounds(20, 89, (width - 50), height - 130);
    frame.getContentPane().add(pnlGrind1);
    pnlGrind1.setLayout(null);
    pnlGrind1.setBorder(BorderFactory.createLineBorder (Color.blue, 2));
    pnlGrind1.setVisible(false);
    pnlGrind1.setBackground(new Color(255, 0, 204)); // Used to see panel
    // better
    // Left Side
    lblWeekSummary = new JLabel("Week Summary (Measured at Buffing)");
    lblWeekSummary.setBounds(0, 0, 515, 37);
    pnlGrind1.add(lblWeekSummary);
    lblWeekSummary.setFont(new Font("Tahoma", Font.PLAIN, 30));
    // Spacing
    lblCustom1 = new JLabel("Custom:");
    lblCustom1.setBounds(0,
            lblWeekSummary.getY() + (lblWeekSummary.getHeight() + margin)
                    * 2, 515, labelHeight);
    pnlGrind1.add(lblCustom1);
    lblCustom1.setFont(defaultFont);
    lblCustom1.setForeground(OrangeRed);
    lblRepairCredit = new JLabel("Repair Credit:");
    lblRepairCredit.setBounds(0,
            lblCustom1.getY() + (lblCustom1.getHeight() + margin), 515,
            labelHeight);
    pnlGrind1.add(lblRepairCredit);
    lblRepairCredit.setFont(defaultFont);
    lblRepairCredit.setForeground(DodgerBlue);
    // Spacing
    lblQC = new JLabel("QC");
    lblQC.setBounds(
            0,
            (int) (lblRepairCredit.getY() + (lblRepairCredit.getHeight() + margin) * 1.5),
            515, labelHeight);
    pnlGrind1.add(lblQC);
    lblQC.setFont(defaultFont);
    lblQC.setForeground(DarkGreen);
    lblCustom2 = new JLabel("Custom:");
    lblCustom2.setBounds(0, lblQC.getY() + (lblQC.getHeight() + margin),
            515, labelHeight);
    pnlGrind1.add(lblCustom2);
    lblCustom2.setFont(defaultFont);
    lblCustom2.setForeground(DarkGreen);
    lblRepair = new JLabel("Repair:");
    lblRepair.setBounds(0, lblCustom2.getY()
            + (lblCustom2.getHeight() + margin), 515, labelHeight);
    pnlGrind1.add(lblRepair);
    lblRepair.setFont(defaultFont);
    lblRepair.setForeground(DarkGreen);
    // End Left Side
    // Right Side

    // End Right Side
    // End Grinding Layout 1
// END MASSIVE CHUNK OF LAYOUT CODE //
    frame.pack();
    frame.setExtendedState(frame.getExtendedState() | JFrame.MAXIMIZED_BOTH); // Maximize
    // Window
}
// Thread classes

public void getData() {
    ActionListener updateData = new ActionListener() {
        public void actionPerformed(ActionEvent evt) {
            pnlGrind1.repaint();
            pnlGrind2.repaint();
            countDown = 15;
        }
    };
    refresh = new Timer(refreshRate, updateData);
    refresh.start();
}
// End Thread Classes

public void actionPerformed(ActionEvent e) { // Combo box to select team was
                                                // clicked
    int team;
    team = cmbTeamNames.getSelectedIndex();
    currentTeam = team;
    countDown=600;
    int t2Interval = 5000;
    if (team == 1) { // Grinding team
        pnlGrind1.setVisible(true);
    }
    ActionListener alternatePnl = new ActionListener() {
        public void actionPerformed(ActionEvent evt) {
            // updateData();
            alternatePanel(cmbTeamNames.getSelectedIndex());
        }
    };
    new Timer(t2Interval, alternatePnl).start();
}

void alternatePanel(int team) {
    if (team == 1) { // If Grinding team
        if (pnlGrind1.isVisible()) {
            pnlGrind1.setVisible(false);
            pnlGrind2.setVisible(true);
        } else {
            pnlGrind2.setVisible(false);
            pnlGrind1.setVisible(true);
        }
    }
}

}

Answer 1

因为jpanel的高度和宽度为负:

pnlGrind2.setBounds(20, 89, (width - 50), height - 130);

， width = height = 0。您刚刚初始化了JFrame，因此默认值为0，并且您立即将这些值分配给height和width。

如果已经做了绝对布局，保持一致并尽快指定你的帧大小:

private void initialize() {
    frame = new JFrame();
    frame.setSize(800, 600);
    ...

之后，jpanel出现在我的Ubuntu机器的屏幕上。