Question

我已经使用GroupLayout在JPanel上定位组件，但我似乎无法让它工作。当我在水平和垂直组中注释掉前6个组件时，它工作正常，但我需要这些组件。所有组件都存在于水平和垂直组中，因此不应该是问题。这是代码

JPanel centerPanel = new JPanel();

GroupLayout layoutCenterPanel = new GroupLayout(centerPanel);
layoutCenterPanel.setAutoCreateGaps(true);
layoutCenterPanel.setAutoCreateContainerGaps(true);

centerPanel.setLayout(layoutCenterPanel);

layoutCenterPanel.setHorizontalGroup(
     layoutTopPanel.createSequentialGroup()
     .addGroup(layoutCenterPanel.createParallelGroup()
        .addGroup(layoutCenterPanel.createSequentialGroup()
            .addComponent(fileTypeComboBox)
            .addComponent(fileExtensionComboBox)
            .addComponent(locationComboBox)
        )
        .addGroup(layoutCenterPanel.createSequentialGroup()
            .addComponent(jScrollPane1)
            .addComponent(jScrollPane2)
            .addComponent(jScrollPane3)
        )
     )
     .addGroup(layoutCenterPanel.createParallelGroup()
        .addComponent(searchFileContent)
        .addComponent(searchHiddenFiles)
        .addComponent(searchArchivedFiles)
        .addComponent(searchReadOnlyFiles)
        .addComponent(indexOnly)
        .addComponent(entireSpace)
     )
);


layoutCenterPanel.setVerticalGroup(
     layoutCenterPanel.createParallelGroup()
     .addGroup(layoutCenterPanel.createSequentialGroup()
        .addGroup(layoutCenterPanel.createParallelGroup()
            .addComponent(fileTypeComboBox)
            .addComponent(fileExtensionComboBox)
            .addComponent(locationComboBox)
        )
        .addGroup(layoutCenterPanel.createParallelGroup()
            .addComponent(jScrollPane1)
            .addComponent(jScrollPane2)
            .addComponent(jScrollPane3)
        )
     )
     .addGroup(layoutCenterPanel.createSequentialGroup()
        .addComponent(searchFileContent)
        .addComponent(searchHiddenFiles)
        .addComponent(searchArchivedFiles)
        .addComponent(searchReadOnlyFiles)
        .addComponent(indexOnly)
        .addComponent(entireSpace)
      )
);
add(centerPanel);

...和stacktrace的一部分

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.swing.GroupLayout.areParallelSiblings(GroupLayout.java:1175)
at javax.swing.GroupLayout.access$1000(GroupLayout.java:208)
at javax.swing.GroupLayout$AutoPreferredGapSpring.addTarget(GroupLayout.java:3338)
at javax.swing.GroupLayout$ParallelGroup.insertAutopadding(GroupLayout.java:2619)
at javax.swing.GroupLayout$SequentialGroup.insertAutopadding(GroupLayout.java:2232)
at javax.swing.GroupLayout$SequentialGroup.insertAutopadding(GroupLayout.java:2232)
at javax.swing.GroupLayout.insertAutopadding(GroupLayout.java:1144)

我无法弄清楚为什么这个GroupLayout无法正常工作。错误：java.lang.NullPointerException

0 个答案: