创建窗体,在窗体上添加三个按钮,“读文件”,“写文件”,“清空”。
要求:
点击“读文件”按钮读取文件的内容,并显示在文本域中;
点击“写文件”按钮将 中
点击“清空”按钮,清楚文本域中的内容。
输入答案
```java
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedReader;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.OutputStreamWriter;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.filechooser.FileNameExtensionFilter;
public class Notepad extends JFrame implements ActionListener{
JTextArea jta = null;
JScrollPane jsp = null;
// 菜单条
JMenuBar jmb = null;
// 第一个JMenu
JMenu file = null;
JMenuItem open = null;
JMenuItem save = null;
JMenuItem clean = null;
JMenuItem exit = null;
public static void main(String[] args){
new Notepad();
}
Notepad() {
jta = new JTextArea();
jsp = new JScrollPane(jta);
jmb = new JMenuBar();
file = new JMenu("文件(F)");
// 设置助记符:使用alt+F可以激活相应的事件
file.setMnemonic('F');
open = new JMenuItem("打开(O)");
open.setMnemonic('O');
save = new JMenuItem("保存(S)");
save.setMnemonic('S');
clean = new JMenuItem("清空(C)");
clean.setMnemonic('C');
exit = new JMenuItem("退出(X)");
exit.setMnemonic('X');
file.setActionCommand("file");
open.setActionCommand("open");
open.addActionListener(this);
save.setActionCommand("save");
save.addActionListener(this);
clean.setActionCommand("clean");
clean.addActionListener(this);
exit.setActionCommand("exit");
exit.addActionListener(this);
this.setJMenuBar(jmb);
jmb.add(file);
file.add(open);
file.add(save);
file.add(clean);
file.add(exit);
this.add(jsp);
this.setTitle("记事本");
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setVisible(true);
this.setBounds(300, 200, 400, 300);
}
public void actionPerformed(ActionEvent e){
if (e.getActionCommand().equals("open")){
JFileChooser jfc = new JFileChooser();
FileNameExtensionFilter filter = new FileNameExtensionFilter("txt","txt");
jfc.setDialogTitle("请选择文件");
jfc.setFileFilter(filter);
int ret = jfc.showOpenDialog(null);
if(ret != JFileChooser.APPROVE_OPTION){
return;
}
String filename = jfc.getSelectedFile().getAbsolutePath();
try {
BufferedReader in = new BufferedReader(new FileReader(filename));
String line = null;
jta.setText("");
while((line = in.readLine())!=null){
jta.setText(jta.getText() +line+ System.getProperty("line.separator"));
}
in.close();
} catch (IOException e1) {
e1.printStackTrace();
}
}
if (e.getActionCommand().equals("save")){
JFileChooser jfc = new JFileChooser();
jfc.setDialogTitle("另存为");
// 按默认的方式显示
jfc.showSaveDialog(null);
jfc.setVisible(true);
// 得到用户希望保存的路劲
String file = jfc.getSelectedFile().getAbsolutePath();
String str = jta.getText();
try {
FileOutputStream fos = new FileOutputStream(file);
OutputStreamWriter ow = new OutputStreamWriter(fos);
ow.write(str);
ow.flush();
ow.close();
fos.close();
} catch (IOException e1) {
e1.printStackTrace();
}
}
if (e.getActionCommand().equals("clean")){
jta.setText("");
}
if (e.getActionCommand().equals("exit")){
System.exit(0);
}
}
}
```
支持，打开文件，保存文件，清空文本内容