Java-BoxLayout

Question

我正在使用 BoxLayout 来定位服务器 GUI 的 GUI 元素。我的 JLabels 发生了一件奇怪的事情。我想知道为什么当我将字符串附加到 JTextArea 时，JLabels 会从其原始位置移动。所以第一个图是位于正确位置的 JLabels。第二张图片是 JLabels 倾斜的

图1

图2

下面是服务器 GUI 的代码

GUI.java

package serverGUI;

import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.Dimension;
import javax.swing.BorderFactory;
import javax.swing.Box;
import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextArea;

public class GUI extends JFrame{

    public JTextArea serverInfo;
    public JButton serverRunningState;
    public JLabel serverConnectionStatus = new JLabel(GUIConfig.DEFAULT_SERVER_STATUS);
    public JLabel serverInfoLabel = new JLabel(GUIConfig.DEFAULT_SERVER_EVENT_LABEL);

    public GUI(){
        super("Yahtzee Game Server");

        //set the server online/off-line status to default color
        serverConnectionStatus.setForeground(GUIConfig.DEFAULT_SERVER_STATUS_COLOR);

        //create the server events text area. It will hold all info
        //about server events including client connections/disconnections
        serverInfo = new JTextArea();
        serverInfo.setEditable(false);
        serverInfo.setPreferredSize(new Dimension(350, 450));

        //create the connect/disconnect button. Will be connect when server 
        //is not connected and disconnect when server is connected
        serverRunningState = new JButton();
        serverRunningState.setText("Run Server");

        //Create JPanel with box layout
        JPanel guiPanel = new JPanel();
        guiPanel.setLayout(new BoxLayout(guiPanel, BoxLayout.PAGE_AXIS));

        //add components to panel
        guiPanel.add(serverInfoLabel);
        guiPanel.add(Box.createRigidArea(new Dimension(0,5)));
        guiPanel.add(serverInfo);
        guiPanel.add(Box.createRigidArea(new Dimension(0,5)));
        guiPanel.add(serverConnectionStatus);

        //create a bit of space around components so they get away from edges
        guiPanel.setBorder(BorderFactory.createEmptyBorder(10,10,10,10));

        //add panel to frame
        add(guiPanel, BorderLayout.CENTER);

        //create new panel for buttons
        JPanel buttonPanel = new JPanel();
        buttonPanel.setLayout(new BoxLayout(buttonPanel, BoxLayout.PAGE_AXIS));

        //add connection button
        serverRunningState.setAlignmentX(Component.CENTER_ALIGNMENT);
        buttonPanel.add(serverRunningState);
        buttonPanel.add(Box.createRigidArea(new Dimension(0,5)));
        //add panel to frame
        add(buttonPanel, BorderLayout.SOUTH);

        //set size, do not allow resize and show
        setSize(GUIConfig.DEFAULT_FRAME_WIDTH, GUIConfig.DEFUALT_FRAME_HEIGHT);
        setResizable(false);
        setVisible(true);

        //set it to terminate frame on exit
        setDefaultCloseOperation(EXIT_ON_CLOSE);
    }

    public static void main(String args[]) {
        GUI g = new GUI();
    }
}

ActionListener 代码 (ServerController.java):

package serverController;

import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import serverGUI.GUI;
import serverModel.AppServer;
import serverModel.Config;

public class ServerController {

    public AppServer server;
    public GUI serverGUI;

    public ServerController() {
        super();

        //create the view and add an action listener to know when run server
        //button is pressed
        serverGUI = new GUI();

        //add action listener on run server button
        serverGUI.serverRunningState.addActionListener(new ActionListener()
                {
                    public void actionPerformed(ActionEvent e) {
                        //start server and disable run server button. change its text to server running
                        server = new AppServer(Config.DEFAULT_PORT);

                        if(server.isRunning() == true){
                            serverGUI.serverRunningState.setEnabled(false);
                            serverGUI.serverRunningState.setText("Server Running");
                            serverGUI.serverInfo.append("Server started!\nWaiting for new clients...\n\n");
                            serverGUI.serverInfo.setLineWrap(true);

                            //change JLabel to "Server Online" from "Server Off-line"
                            serverGUI.serverConnectionStatus.setText("Server Online");
                            serverGUI.serverConnectionStatus.setForeground(Color.GREEN);
                        }
                    }
                });
    }

    public void updateServerEventLog() {}

    private void checkServerStatus(AppServer s) {

    }

    public static void main(String args[]) {
        ServerController sController = new ServerController();
    }

}

Answer 1

出现此行为的原因是，一旦向 JTextArea 添加内容，整个 JPanel 就必须重新绘制。而且由于您没有明确设置对齐方式，Swing 会将其对齐到中心，从而弄乱您的 UI。

您需要使用 BoxLayout 显式指定 JPanel 内所有组件的对齐方式:

    //add components to panel
    serverInfoLabel.setAlignmentX(Component.LEFT_ALIGNMENT);
    guiPanel.add(serverInfoLabel);
    guiPanel.add(Box.createRigidArea(new Dimension(0,5)));
    serverInfo.setAlignmentX(Component.LEFT_ALIGNMENT);
    guiPanel.add(serverInfo);
    guiPanel.add(Box.createRigidArea(new Dimension(0,5)));
    serverConnectionStatus.setAlignmentX(Component.LEFT_ALIGNMENT);
    guiPanel.add(serverConnectionStatus);

添加后应该可以工作。