如何将JTextArea添加到此代码中?

Question

请设置默认文本。我试图使一个文本区域，显示文件的内容。我计划使用java库中的文件打开器来选择文件。我将把文件内容存储在一个字符串中，然后在JtextArea中打印出来。

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
public class Parser implements ActionListener {
protected JTextArea textArea;
Parser() {
    JFrame f = new JFrame("DECA Test Parser");
    f.setSize(400, 400);
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    JMenuBar jmb = new JMenuBar();
    JMenu jmFile = new JMenu("File");
    JMenuItem jmiOpen = new JMenuItem("Open");
    JMenuItem jmiSave = new JMenuItem("Save");
    JMenuItem jmiExit = new JMenuItem("Exit");
    jmFile.add(jmiOpen);
    jmFile.add(jmiSave);
    jmFile.addSeparator();
    jmFile.add(jmiExit);
    jmb.add(jmFile);
    JMenu jmHelp = new JMenu("Help");
    JMenuItem jmiAbout = new JMenuItem("About");
    jmHelp.add(jmiAbout);
    jmb.add(jmHelp);
    jmiOpen.addActionListener(this);
    jmiSave.addActionListener(this);
    jmiExit.addActionListener(this);
    jmiAbout.addActionListener(this);

    f.setJMenuBar(jmb);
    f.setVisible(true);

}
public void actionPerformed(ActionEvent ae) {
    String comStr = ae.getActionCommand();
    if (comStr == "Exit");
        System.exit(0);
}
public static void main(String args[]) {
    new Parser();
}
}

Answer 1

您可以通过添加以下几行添加textArea:

textArea = new JTextArea(); 
f.add(textArea);

然后，你可以像这样添加文本:

textArea.setText("your file content here");

Answer 2

//  Go through this code it reads a file named read.txt in c drive and prints its content to text area  

    import java.awt.event.ActionEvent;
    import java.awt.event.ActionListener;
    import java.io.BufferedReader;
    import java.io.DataInputStream;
    import java.io.File;
    import java.io.FileInputStream;
    import java.io.FileNotFoundException;
    import java.io.FileReader;
    import java.io.IOException;
    import java.io.InputStreamReader;
    import javax.swing.JFrame;
    import javax.swing.JMenu;
    import javax.swing.JMenuBar;
    import javax.swing.JMenuItem;
    import javax.swing.JScrollPane;
    import javax.swing.JTextArea;
    public class Test implements ActionListener {
    protected JTextArea textArea;
    Test() throws IOException {
        JFrame f = new JFrame("DECA Test Parser");
        f.setSize(400, 400);
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JMenuBar jmb = new JMenuBar();
        JMenu jmFile = new JMenu("File");
        JMenuItem jmiOpen = new JMenuItem("Open");
        JMenuItem jmiSave = new JMenuItem("Save");
        JMenuItem jmiExit = new JMenuItem("Exit");
        jmFile.add(jmiOpen);
        jmFile.add(jmiSave);
        jmFile.addSeparator();
        jmFile.add(jmiExit);
        jmb.add(jmFile);
        JMenu jmHelp = new JMenu("Help");
        JMenuItem jmiAbout = new JMenuItem("About");
        jmHelp.add(jmiAbout);
        jmb.add(jmHelp);
        jmiOpen.addActionListener(this);
        jmiSave.addActionListener(this);
        jmiExit.addActionListener(this);
        jmiAbout.addActionListener(this);
        textArea = new JTextArea();
        FileInputStream fstream = new FileInputStream("C:\read.txt");
        // Get the object of DataInputStream
        DataInputStream in = new DataInputStream(fstream);
        BufferedReader br = new BufferedReader(new InputStreamReader(in));
        String strLine;
        //Read File Line By Line
        while ((strLine = br.readLine()) != null)   {
        // Print the content on the console
          textArea.append(strLine);
        } 
        f.getContentPane().add(textArea);
        f.setJMenuBar(jmb);
        f.setVisible(true);

    }
    public void actionPerformed(ActionEvent ae) {
        String comStr = ae.getActionCommand();
        if (comStr == "Exit");
            System.exit(0);
    }
    public static void main(String args[]) {
        try {
            new Test();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    }

Answer 3

JTextArea扩展了JTextComponent, JTextComponent有两个方法

public void read(Reader in, Object desc)
public void write(Writer out)

把FileReader/FileWriter传过去。