Exception in thread "main" java.lang.NullPointerException
at com.txw.Ftest.getControlPanel(Ftest.java:28)
at com.txw.Ftest.getJContentPane(Ftest.java:93)
at com.txw.Ftest.initialize(Ftest.java:85)
at com.txw.Ftest.<init>(Ftest.java:81)
at com.txw.Ftest.main(Ftest.java:99)
public class Ftest extends JFrame {
private JScrollPane scrollPane;
private static final long serialVersionUID=1L;
private JPanel jContentPane=null;
private JTextArea jTextArea=null;
private JPanel controlPanel=null;
private JButton openButton=null;
private JButton closeButton=null;
private JTextArea getJTextArea(){
if(jTextArea==null){
jTextArea=new JTextArea();
}
return jTextArea;
}
private JPanel getControlPanel(){
if(controlPanel==null){
FlowLayout flowLayout=new FlowLayout();
flowLayout.setVgap(1);
controlPanel=new JPanel(); //缺少此行就会报错
controlPanel.setLayout(flowLayout);
controlPanel.add(getOpenButton(), null);
controlPanel.add(getCloseButton(),null);
}
return controlPanel;
}
private JButton getOpenButton(){
if(openButton==null){
openButton=new JButton();
openButton.setText("写入文件");
openButton
//.addActionListener(new java.awt.event.ActionListerner(){
//java.awt.event.ActionListerner cannot be resolved to a type, "ActionListerner"字母写错，改为“ActionListener”
.addActionListener(new java.awt.event.ActionListener(){
public void actionPerformed(ActionEvent e){
File file=new File("word.txt");
try{
FileWriter out=new FileWriter(file);
String s=jTextArea.getText();
out.write(s);
out.close();
}catch(Exception e1){
e1.printStackTrace();
}
}
});
}
return openButton;
}
private JButton getCloseButton(){
if(closeButton==null){
closeButton=new JButton();
closeButton.setText("读取文件");
closeButton
.addActionListener(new java.awt.event.ActionListener(){
public void actionPerformed(ActionEvent e){
File file=new File("word.txt");
try{
FileReader in=new FileReader(file);
char byt[]=new char[1024];
int len=in.read(byt);
jTextArea.setText(new String(byt,0,len));
in.close();
}catch(Exception e1){
e1.printStackTrace();
}
}
});
}
return closeButton;
}
public Ftest(){
super();
initialize();
}
private void initialize(){
this.setSize(300,200);
this.setContentPane(getJContentPane());
this.setTitle("JFrame");
}
private JPanel getJContentPane(){
if(jContentPane==null){
jContentPane=new JPanel();
jContentPane.setLayout(new BorderLayout());
jContentPane.add(getScrollPane(), BorderLayout.CENTER);
jContentPane.add(getControlPanel(),BorderLayout.SOUTH);
}
return jContentPane;
}
public static void main(String[] args) {
// TODO Auto-generated method stub
Ftest thisClass=new Ftest();
thisClass.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
thisClass.setVisible(true);
}
protected JScrollPane getScrollPane(){
if(scrollPane==null){
scrollPane=new JScrollPane();
scrollPane.setViewportView(getJTextArea());
}
return scrollPane;
}
}