关于组布局

Question

嗨，我

试图实现组布局，我的赋值要求下面是我的代码片段，但是当我做pack（）时，我在这个代码片段中遇到了一个问题; 它也抛出异常，我不知道如何使其可见，请指导我在哪里错误 代码建议会有所帮助

提前致谢

public class AMS_GUI extends JFrame
{
   private JFrame frame;

public AMS_GUI()
{
  makeFrame(); 
}
public void makeFrame()
{
   JLabel unitLabel = new JLabel("Units"); // units label
   JComboBox unitCombo = new JComboBox(); // units empty combo box
   JButton addUnit = new JButton("Add"); // add units button for adding units
   JLabel AssessmentLabel = new JLabel("Assessments"); // assessments Label
   JComboBox AssessmentCombo = new JComboBox(); // assessments empty combo box
   JButton addAssessment = new JButton("Add"); // assessments add button
   JLabel TasksLabel = new JLabel("Tasks"); // tasks Label
   JComboBox TasksCombo = new JComboBox(); // tasks empty combo box
   JButton addTasks = new JButton("Add"); // tasks add button
   JButton editTasks = new JButton("Edit");// tasks Edit button
   JLabel planLabel = new JLabel("Plans");
   JButton makePlan = new JButton("MakePlan");
   JButton showPlan = new JButton("ShowPlan");
   JButton savePlan = new JButton("SavePlan");
    //Set up the content pane.
    GroupLayout layout = new GroupLayout(getContentPane());
    getContentPane().setLayout(layout);
    layout.setAutoCreateGaps(true);
    layout.setAutoCreateContainerGaps(true);
    layout.setHorizontalGroup(layout.createSequentialGroup()
        .addComponent(unitLabel)
        .addComponent(AssessmentLabel)
        .addComponent(TasksLabel)
        .addComponent(planLabel)
        .addGroup(layout.createParallelGroup(LEADING)
        .addComponent(unitCombo)
        .addComponent(AssessmentCombo)
        .addComponent(TasksCombo)
        .addComponent(makePlan)
        .addComponent(showPlan)
        .addComponent(savePlan))
        .addGroup(layout.createParallelGroup(LEADING)
            .addComponent(addUnit)
            .addComponent(addAssessment)
            .addComponent(addTasks)
            .addComponent(editTasks)
            )
            );

        setTitle("AMS_GUI");
        pack();

例外

Exception in thread "main" java.lang.IllegalStateException: javax.swing.JButton
    [,0,0,0x0,invalid,alignmentX=0.0,alignmentY=0.5,
    border=javax.swing.plaf.BorderUIResource$CompoundBorderUIResource@bb6ab6,flags=296,
    maximumSize=,minimumSize=,preferredSize=,defaultIcon=,disabledIcon=,disabledSelectedIcon=,
    margin=javax.swing.plaf.InsetsUIResource[top=2,left=14,bottom=2,right=14],paintBorder=true,
    paintFocus=true,pressedIcon=,rolloverEnabled=true,rolloverIcon=,rolloverSelectedIcon=,
    selectedIcon=,text=Edit,defaultCapable=true] 
    is not attached to a vertical group

Answer 1

Exception in thread "main" java.lang.IllegalStateException: javax.swing.JButton
    [..] 
    is not attached to a vertical group

添加

垂直组并向其中添加组件。

来自JavaDocs：

GroupLayout独立处理每个轴。也就是说，有一个组代表水平轴，一个组代表垂直轴。水平组负责确定沿水平轴的最小、首选和最大尺寸，以及设置其中包含的组件的 x 和宽度。垂直组负责确定沿垂直轴的最小、首选和最大尺寸，以及设置其中包含的组件的 y 和高度。每个Component必须同时存在于水平和垂直组中，否则在布局期间或请求最小、首选或最大大小时会引发IllegalStateException。