IllegalStateException 错误。使用 GroupLayout() 布局组件时

Question

Java 中的 GUI 新手，我正在尝试使用 GroupLayouts 来布局图形组件，我做错了，但不知道是什么。我找不到导致此错误的原因。迫切需要帮助。

线程“main”中的异常线程“AWT-EventQueue-0”中的异常java.lang.IllegalStateException：

at javax.swing.GroupLayout.checkComponents(Unknown Source)
at javax.swing.GroupLayout.prepare(Unknown Source)
at javax.swing.GroupLayout.layoutContainer(Unknown Source)
at java.awt.Container.layout(Unknown Source)
at java.awt.Container.doLayout(Unknown Source)
at java.awt.Container.validateTree(Unknown Source)
at java.awt.Container.validateTree(Unknown Source)
at java.awt.Container.validateTree(Unknown Source)
at java.awt.Container.validateTree(Unknown Source)
at java.awt.Container.validate(Unknown Source)
at java.awt.Container.validateUnconditionally(Unknown Source)
at java.awt.Window.show(Unknown Source)
at java.awt.Component.show(Unknown Source)
at java.awt.Component.setVisible(Unknown Source)
at java.awt.Window.setVisible(Unknown Source)
at AlignTest.main(AlignTest.java:12)

java.lang.IllegalStateException：

这是代码：

import javax.swing.GroupLayout;
import javax.swing.JButton;
import javax.swing.JCheckBox;enter code here
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;


public class AlignFrame extends JFrame {


    private JTextField xTField;
    private JTextField yTField;

    private JLabel xLabel;
    private JLabel yLabel;

    private JCheckBox sToGr;
    private JCheckBox showGrid;

    private JButton okButton;
    private JButton cancelButton;
    private JButton helpButton;

    public AlignFrame()
    {
        super("Align");
        GroupLayout layout = new GroupLayout(getContentPane());
        getContentPane().setLayout(layout);

        xLabel = new JLabel("X: ");
        yLabel = new JLabel("Y: ");

        xTField = new JTextField("");
        yTField = new JTextField("");

        sToGr= new JCheckBox("Snap to Grid");
        showGrid = new JCheckBox("Show Grid");

        okButton = new JButton("OK");
        cancelButton = new JButton("Cancel");
        helpButton = new JButton("Help");

        layout.setAutoCreateContainerGaps(true);
        layout.setAutoCreateGaps(true);

        layout.setHorizontalGroup(layout.createSequentialGroup()
                .addGroup(layout.createParallelGroup(GroupLayout.Alignment.LEADING)
                        .addComponent(sToGr)
                        .addComponent(showGrid)
                        )
                .addGroup(layout.createParallelGroup(GroupLayout.Alignment.LEADING)
                        .addGroup(layout.createSequentialGroup()
                                .addGroup(layout.createParallelGroup(GroupLayout.Alignment.LEADING)
                                        .addComponent(xLabel)
                                        .addComponent(yLabel))
                                .addGroup(layout.createParallelGroup(GroupLayout.Alignment.LEADING)
                                        .addComponent(xTField)
                                        .addComponent(yTField))
                                )
                        )
                .addGroup(layout.createParallelGroup(GroupLayout.Alignment.LEADING)
                        .addComponent(okButton)
                        .addComponent(cancelButton)
                        .addComponent(helpButton))
                );

        layout.setVerticalGroup(layout.createSequentialGroup()
                .addGroup(layout.createParallelGroup(GroupLayout.Alignment.LEADING)
                        .addComponent(sToGr)
                        .addComponent(showGrid)
                        )
                .addGroup(layout.createParallelGroup(GroupLayout.Alignment.LEADING)
                        .addComponent(xLabel)
                        .addComponent(yLabel))
                .addGroup(layout.createParallelGroup(GroupLayout.Alignment.LEADING)                     
                        .addComponent(okButton)
                        .addComponent(cancelButton)
                        .addComponent(helpButton))

                );
    }

}


####################################################################
############### AlignTest class that contains main #################
####################################################################

import javax.swing.JFrame;


public class AlignTest {

    public static void main(String [] args)
    {
        AlignFrame test = new AlignFrame();

        test.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        test.setSize(500, 500);
        test.setVisible(true);


    }

}

Answer 1

实际异常包含相关信息：

java.lang.IllegalStateException: javax.swing.JTextField[...这里有很多垃圾...] 没有附加到垂直组

你在打电话

layout.setHorizontalGroup(...)

和

layout.setVerticalGroup(...)

但在后者中，JTextFields（xTField 和yTField）没有出现。虽然这可以通过插入这些行来“修复”......

...
.addGroup(layout.createParallelGroup(GroupLayout.Alignment.LEADING)
    .addComponent(xLabel)
    .addComponent(yLabel)
    .addComponent(xTField) // <---
    .addComponent(yTField) // <---
)

在垂直组中，我强烈建议您看看http://docs.oracle.com/javase/tutorial/uiswing/layout/index.html。也许我只是不是“可视化 GUI 编辑器”的忠实粉丝，但我认为只有在确定没有人需要再次查看代码时才应该使用它们。 （这很少发生 - 得出你的结论......）