为什么swing GUI表单生成器不会生成二进制类文件/ java源代码？ [重复]

Question

此问题已经在这里有了答案：

IntelliJ IDEA UI Designer form elements initialize to null（1个答案）

关闭10小时前。

这是我的项目：https://github.com/Kolyall/GUIExample

MainClass

import javax.swing.*;

public class MainClass {

    public static void main(String[] args) {
        SwingUtilities.invokeLater(MainFrame::new);
    }

}

MainFrame

import javax.swing.*;
import java.awt.*;

public class MainFrame extends JFrame {

    public MainFrame() {
        super("MainFrame");
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setMinimumSize(new Dimension(850, 650));
        setSize(new Dimension(850, 650));


        JPanel rootPanel = new JPanel();
        rootPanel.setLayout(new BoxLayout(rootPanel, BoxLayout.X_AXIS));
        getContentPane().add(rootPanel);
        setLocationRelativeTo(null);
        setVisible(true);

        ButtonsFrame buttonsFrame = new ButtonsFrame()
        rootPanel.add(buttonsFrame.buttonsPanel);//java.lang.NullPointerException in this line
    }

}

ButtonsFrame

import javax.swing.*;

public class ButtonsFrame {
    public JButton button1Button;
    public JButton button2Button;
    public JPanel buttonsPanel;
}

ButtonsFrame.form

<?xml version="1.0" encoding="UTF-8"?>
<form xmlns="http://www.intellij.com/uidesigner/form/" version="1" bind-to-class="com.github.kolyall.test.ButtonsFrame">
  <grid id="27dc6" binding="buttonsPanel" layout-manager="GridLayoutManager" row-count="2" column-count="2" same-size-horizontally="false" same-size-vertically="false" hgap="-1" vgap="-1">
    <margin top="0" left="0" bottom="0" right="0"/>
    <constraints>
      <xy x="20" y="20" width="500" height="400"/>
    </constraints>
    <properties/>
    <border type="none"/>
    <children>
      <component id="70295" class="javax.swing.JButton" binding="button1Button" default-binding="true">
        <constraints>
          <grid row="0" column="0" row-span="1" col-span="1" vsize-policy="0" hsize-policy="3" anchor="0" fill="1" indent="0" use-parent-layout="false"/>
        </constraints>
        <properties>
          <text value="Button1"/>
        </properties>
      </component>
      <vspacer id="3d1dd">
        <constraints>
          <grid row="1" column="0" row-span="1" col-span="1" vsize-policy="6" hsize-policy="1" anchor="0" fill="2" indent="0" use-parent-layout="false"/>
        </constraints>
      </vspacer>
      <component id="76c52" class="javax.swing.JButton" binding="button2Button" default-binding="true">
        <constraints>
          <grid row="0" column="1" row-span="1" col-span="1" vsize-policy="0" hsize-policy="3" anchor="0" fill="1" indent="0" use-parent-layout="false"/>
        </constraints>
        <properties>
          <text value="Button2"/>
        </properties>
      </component>
    </children>
  </grid>
</form>

但是运行MainClass.main()之后发生错误：

Exception in thread "AWT-EventQueue-1" java.lang.NullPointerException
    at java.awt.Container.addImpl(Container.java:1095)
    at java.awt.Container.add(Container.java:419)
    at com.github.kolyall.test.MainFrame.<init>(MainFrame.java:29)

似乎IntelliJ IDEA不会生成二进制类文件，但是该选项已启用，我还尝试了“ Java源代码”

UPDATE： Idea的已知问题 Why swing GUI form builder doesn't generate binary class files/java source code?

Answer 1

这与二进制代码生成无关。您的代码看起来丑陋和错误。

ButtonsFrame buttonsFrame = new ButtonsFrame()
rootPanel.add(buttonsFrame.buttonsPanel);

您在这里得到了NPE，因为尚未在ButtonsFrame类中初始化buttonsPanel。

例如：

public class ButtonsFrame {
    public JButton button1Button = new JButton("OK");
    public JButton button2Button = new JButton("Cancel");
    public JPanel buttonsPanel = new JPanel();
}

但是公共成员变量在OOP中不受欢迎。更好的方法是提供一种创建可立即使用的按钮面板的方法。

public class ButtonsFrame {
    private JButton button1Button = new JButton("OK");
    private JButton button2Button = new JButton("Cancel");
    private JPanel buttonsPanel = new JPanel();

    public JPanel createButtonsPanel() {
        buttonsPanel.removeAll();
        buttonsPanel.add(button1Button);
        buttonsPanel.add(button2Button);
        return buttonsPanel;
    }
}

并稍后使用：

rootPanel.add(buttonsFrame.createButtonsPanel());