Java 选中JCheckbox时,标签中未显示文本
我有一个JCheckbox,当单击复选框时,我想在标签中设置文本 到目前为止,我已在复选框和标签的框架内声明了变量和设置:Java 选中JCheckbox时,标签中未显示文本,java,swing,awt,Java,Swing,Awt,我有一个JCheckbox,当单击复选框时,我想在标签中设置文本 到目前为止,我已在复选框和标签的框架内声明了变量和设置: JCheckBox chckbxIncludeExt; JLabel lblNewLabel_1; JCheckBox chckbxIncludeExt = new JCheckBox("Include ext"); chckbxIncludeExt.setForeground(UIManager.getColor("Button.background"
JCheckBox chckbxIncludeExt;
JLabel lblNewLabel_1;
JCheckBox chckbxIncludeExt = new JCheckBox("Include ext");
chckbxIncludeExt.setForeground(UIManager.getColor("Button.background"));
chckbxIncludeExt.setBackground(UIManager.getColor("Button.darkShadow"));
chckbxIncludeExt.setBounds(0, 264, 113, 25);
panel.add(chckbxIncludeExt);
JLabel lblNewLabel_1 = new JLabel("");
lblNewLabel_1.setBounds(12, 311, 230, 16);
panel.add(lblNewLabel_1);
我创建了一个类,并在复选框中添加了一个项目侦听器:
CheckboxStatus checkboxd = new CheckboxStatus();
chckbxIncludeExt.addItemListener(checkboxd);
这是我创建的类:
private class CheckboxStatus implements ItemListener{
public void itemStateChanged(ItemEvent event){
if (chckbxIncludeExt.isSelected()){
lblNewLabel_1.setText("You have selected the checkbox");
}
}
}
这给了我一个错误,显示:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at com.example.android.apis.appwidget.VFSTool$CheckboxStatus.itemStateChanged(VFSTool.java:199)
at javax.swing.AbstractButton.fireItemStateChanged(Unknown Source)
错误出现在第199行,标签在第199行设置了文本。当我选中该框时,它会显示此内容,而不会显示文本 您正在对字段进行阴影处理:
JCheckBox chckbxIncludeExt;
...
// and later:
JCheckBox chckbxIncludeExt = new JCheckBox("Include ext");
将后面的更改为:
chckbxIncludeExt = new JCheckBox("Include ext");
您在
lblNewLabel_1
中遇到了相同的问题,您正在对字段进行阴影处理:
JCheckBox chckbxIncludeExt;
...
// and later:
JCheckBox chckbxIncludeExt = new JCheckBox("Include ext");
将后面的更改为:
chckbxIncludeExt = new JCheckBox("Include ext");
lblNewLabel\u 1
如何将chckbxIncludeExt
设置为CheckboxStatus
类?如何将chckbxIncludeExt
设置为CheckboxStatus
类?