BoxLayout:无法设置子组件的大小 [英] BoxLayout: can't setup child component size

问题描述

我有一个 JFrame - SuperTest 和 JPanel - SuperLogin .登录面板具有用户名和密码输入字段以及一个登录按钮.我希望它看起来像这样:

但是它看起来像下面的图片，输入字段的高度和宽度太大.

SuperTest.java :

  import javax.swing.*;公共类SuperTest扩展了JFrame {公共SuperTest(){添加(新的SuperLogin());setVisible(true);setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);setSize(600，400);}公共静态void main(String [] args){SuperTest测试=新的SuperTest();}} 

SuperLogin.java :

  import javax.swing.*;导入java.awt.*;公共类SuperLogin扩展了JPanel {私人JButton loginButton =新的JButton("Login");私人TextField usernameField =新的文本字段()；私人TextField passwordField =新的TextField();公共SuperLogin(){BoxLayout布局=新的BoxLayout(this，BoxLayout.Y_AXIS);setLayout(layout);add(new JLabel("Login")))；添加(用户名字段);添加(passwordField);添加(loginButton);componentSetup();}私有无效componentSetup(){loginButton.setSize(20，10);usernameField.setSize(100，50);passwordField.setSize(100，50);loginButton.setMinimumSize(new Dimension(20，10));usernameField.setMinimumSize(new Dimension(100，50));passwordField.setMinimumSize(new Dimension(100，50));loginButton.setPreferredSize(new Dimension(20，10));usernameField.setPreferredSize(new Dimension(100，50));passwordField.setPreferredSize(new Dimension(100，50));}} 

我读到设置最小值，首选大小就足够了，但是看起来好像还不够.

解决方案

我将所有内容都放在一个类中.代码后的解释.

  import java.awt.Component;导入java.awt.EventQueue;导入javax.swing.BorderFactory;导入javax.swing.Box;导入javax.swing.BoxLayout;导入javax.swing.JButton;导入javax.swing.JFrame;导入javax.swing.JLabel;导入javax.swing.JPanel;导入javax.swing.JPasswordField;导入javax.swing.JTextField;导入javax.swing.WindowConstants;公共类SuperOne实现了Runnable {私有JButton loginButton;私有JFrame框架；私有JPasswordField passwordField;私有JTextField usernameField;@Override公共无效run(){showGui();}私人JPanel createLoginPanel(){JPanel loginPanel =新的JPanel();BoxLayout布局=新的BoxLayout(loginPanel，BoxLayout.PAGE_AXIS);loginPanel.setLayout(layout);loginPanel.setBorder(BorderFactory.createEmptyBorder(20，20，20，20));JLabel loginLabel = new JLabel("Login");loginLabel.setAlignmentX(Component.CENTER_ALIGNMENT);usernameField = new JTextField(10);usernameField.setAlignmentX(Component.CENTER_ALIGNMENT);passwordField =新的JPasswordField(10);passwordField.setAlignmentX(Component.CENTER_ALIGNMENT);loginButton = new JButton("login");loginButton.setAlignmentX(Component.CENTER_ALIGNMENT);loginPanel.add(loginLabel);loginPanel.add(Box.createVerticalStrut(15));loginPanel.add(usernameField);loginPanel.add(Box.createVerticalStrut(5));loginPanel.add(passwordField);loginPanel.add(Box.createVerticalStrut(5));loginPanel.add(loginButton);返回loginPanel;}私人无效的showGui(){frame = new JFrame();frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);frame.add(createLoginPanel());frame.pack();frame.setLocationByPlatform(true);frame.setVisible(true);}/*** 从这里开始.*/公共静态void main(String [] args){EventQueue.invokeLater(new SuperOne());}} 

1. 处理GUI组件的所有代码都必须在事件调度线程(EDT)上运行.尽管不是强制性的，但我还是想通过调用 EventQueue.invokeLater()显式启动EDT.
2. 使用 BoxLayout 上的教程参考网页，该教程显示在

   I have a JFrame - SuperTest and JPanel - SuperLogin. The login panel has the username and password input fields and a login button. I want it to look like this:

   but it looks like the pic below, with input fields having too huge height and width.

   SuperTest.java:

   import javax.swing.*;
   
   public class SuperTest extends JFrame {
       public SuperTest()  {
           add(new SuperLogin());
           setVisible(true);
           setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
           setSize(600, 400);
       }
   
       public static void main(String[] args) {
           SuperTest test = new SuperTest();
       }
   }
   

   SuperLogin.java:

   import javax.swing.*;
   import java.awt.*;
   
   public class SuperLogin extends JPanel {
       private JButton loginButton =
               new JButton("Login");
       private TextField usernameField =
               new TextField();
       private TextField passwordField =
               new TextField();
   
       public SuperLogin()  {
           BoxLayout layout =
                   new BoxLayout(this, BoxLayout.Y_AXIS);
           setLayout(layout);
   
           add(new JLabel("Login"));
   
           add(usernameField);
           add(passwordField);
           add(loginButton);
   
           componentSetup();
       }
   
       private void componentSetup()  {
           loginButton.setSize(20, 10);
           usernameField.setSize(100, 50);
           passwordField.setSize(100, 50);
   
           loginButton.setMinimumSize(new Dimension(20, 10));
           usernameField.setMinimumSize(new Dimension(100, 50));
           passwordField.setMinimumSize(new Dimension(100, 50));
   
           loginButton.setPreferredSize(new Dimension(20, 10));
           usernameField.setPreferredSize(new Dimension(100, 50));
           passwordField.setPreferredSize(new Dimension(100, 50));
   
       }
   }
   

   I read that setting min, preferred size would be enough, but it looks like it's not.

   解决方案

   I put everything into a single class. Explanations after the code.

   import java.awt.Component;
   import java.awt.EventQueue;
   
   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.JPasswordField;
   import javax.swing.JTextField;
   import javax.swing.WindowConstants;
   
   public class SuperOne implements Runnable {
       private JButton  loginButton;
       private JFrame  frame;
       private JPasswordField  passwordField;
       private JTextField  usernameField;
   
       @Override
       public void run() {
           showGui();
       }
   
       private JPanel createLoginPanel() {
           JPanel loginPanel = new JPanel();
           BoxLayout layout = new BoxLayout(loginPanel, BoxLayout.PAGE_AXIS);
           loginPanel.setLayout(layout);
           loginPanel.setBorder(BorderFactory.createEmptyBorder(20, 20, 20, 20));
           JLabel loginLabel = new JLabel("Login");
           loginLabel.setAlignmentX(Component.CENTER_ALIGNMENT);
           usernameField = new JTextField(10);
           usernameField.setAlignmentX(Component.CENTER_ALIGNMENT);
           passwordField = new JPasswordField(10);
           passwordField.setAlignmentX(Component.CENTER_ALIGNMENT);
           loginButton = new JButton("login");
           loginButton.setAlignmentX(Component.CENTER_ALIGNMENT);
           loginPanel.add(loginLabel);
           loginPanel.add(Box.createVerticalStrut(15));
           loginPanel.add(usernameField);
           loginPanel.add(Box.createVerticalStrut(5));
           loginPanel.add(passwordField);
           loginPanel.add(Box.createVerticalStrut(5));
           loginPanel.add(loginButton);
           return loginPanel;
       }
   
       private void showGui() {
           frame = new JFrame();
           frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
           frame.add(createLoginPanel());
           frame.pack();
           frame.setLocationByPlatform(true);
           frame.setVisible(true);
       }
   
       /**
        * Start here.
        */
       public static void main(String[] args) {
           EventQueue.invokeLater(new SuperOne());
       }
   }
   

   1. All code that deals with the GUI components must run on the Event Dispatch Thread (EDT). Although not mandatory, I like to explicitly launch the EDT by calling EventQueue.invokeLater().
   2. Refer to the Web page with the tutorial on BoxLayout that appears in the other answer.
   3. JTextField and JPasswordField both have a columns property. I find that better for setting a desired width than using setPreferredSize()

   Here is a screen capture of the running app.

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