Java JPanel 不会出现在 Linux 中的 JFrame 中

Question

我正在开发一个应用程序，该应用程序查询数据库并将该信息提取到我已添加到 JFrame 的几个 JPanel 上。每隔 30 秒，我在 JFrame 中将其中一个的可见性设置为 false，将另一个的可见性设置为 true，以交替显示其中一个。

该应用程序在 Windows 中运行良好，但是当我将其放在我的 Ubuntu 计算机上(运行 XFCE 和 openjdk-7-jre)时，面板不显示。 JFrame 中的其他组件确实出现了，但我不确定出了什么问题。同样，该程序在 Windows 中运行正确，但在 Ubuntu 中运行不正确。

我试图将我的代码精简为可以自行编译和运行的代码，但我知道我的代码一团糟。我几乎没有做过 Java 编程，所以我很抱歉这一切将变得多么丑陋!我还删除了数据库内容，因为它正在工作，因此你们都不需要看到。

感谢任何能给我指明正确方向的人!

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 获得负高度和宽度:

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

，并且宽度=高度=0。您刚刚初始化了 JFrame，因此默认情况下均为 0，您可以立即将这些值分配给 height 和 width。

如果已经进行绝对布局，请保持一致并尽快指定框架大小:

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

之后 JPanels 出现在我的 Ubuntu 机器的屏幕上。