Question

我有一个bigPanel。 bigPanel内部有多个面板（panel_1，panel_2，panel_3等......）

bigPanel使用GridBagLayout。 panel_1等使用GridLayout。

在另一个面板中，我创建了一个ADD按钮。如果用户单击此按钮，则会出现JDialog，用户必须填写表单：

按钮名称：
数字：
字母：

用户填写完JDialog表单后，将根据JDialog表单创建一个新按钮。

此代码将在用户单击JDialog表单中的FINISHED按钮后执行：

if(Number=="1"){
                    if(Alphabet=="A")
                    {   

                    JButton newButton = new JButton(buttonName);                        
                    //bigPanel.add(newButton);
                    //bigPanel.updateUI();  
                    panel_1.add(newButton);
                    panel_1.updateUI();

                    JOptionPane.showMessageDialog(null,"Successfully added !");
                    }

                    }
                    else if(Alphabet=="B"){
                    JButton newButton = new JButton(buttonName);                        
                    //bigPanel.add(newButton);
                    //bigPanel.updateUI();  
                    panel_2.add(newButton);
                    panel_2.updateUI();

                    JOptionPane.showMessageDialog(null,"Successfully added !");
                    }
                    ...
                }
if (Number=="2"){
                    ...
                    }
                 ...

我用数字1和字母A测试JDialog。目前我得到的结果是在控制台中警告该行有问题：

panel_1.add(newButton);//line 313

警告：

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at UI2$3.actionPerformed(UI2.java:313)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$200(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

未添加按钮。但是，如果我改为

bigPanel.add(newButton);
bigPanel.updateUI();

newButton被添加到bigPanel。不幸的是，我希望将newButton添加到panel_1而不是bigPanel ..

Answer 1

请检查是否添加了panel_1

如何将按钮添加到特定的JPanel中

1 个答案: