java - 启动时将文件打开到 JTextArea

Question

我有一个程序，正在尝试测试是否创建了文件 (info.txt)，如果是，则在程序启动时将内容打开到 JTextArea 中。我该怎么做呢？我已经弄清楚如何搜索并查看文件是否存在，只是无法在启动时将其打开到文本区域

import javax.swing.*; // need it
import java.awt.*;   //need it also
import java.awt.datatransfer.*;
import java.util.*;
import java.io.*;
import java.awt.event.*; //keeps track of events
import javax.swing.border.*; // not necessary / already imported ^^

import javax.swing.*; 
import java.awt.*;   
import java.awt.datatransfer.*;
import java.util.*;
import java.io.*;
import java.awt.event.*; 
import javax.swing.border.*;

public class finalA extends JFrame implements ActionListener{
 private final int WIDTH = 750;
 private final int HEIGHT = 400;
 static String theText;
 private String text;

 //creates components
 private JTextArea textArea;
 private JButton SaveB;
 private JScrollPane scroll;


 public finalA(){
 setTitle("Super fancy text editor");
 setSize(WIDTH,HEIGHT);

  Container pane = getContentPane();

  //Creates button
  SaveB = new JButton("Save & Exit");
  textArea = new JTextArea();
  scroll = new JScrollPane(textArea);
  scroll.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);

  //adds event handler for exit button

  SaveB.addActionListener(this);

  //sets pane to null
  pane.setLayout(null);

  //location of button and TA (750,400)
  textArea.setLocation(10,100);
  SaveB.setLocation(150,320);

  //set size of TA and Button
  textArea.setSize(730,200);
  SaveB.setSize(100,30);

  //add items to pane
  pane.add(textArea);
  pane.add(SaveB);

  scroll.setBounds(10,100,730,200);
  scroll.setVisible(true);

  textArea.setLineWrap(true);
  textArea.setWrapStyleWord(true);
  setDefaultCloseOperation(EXIT_ON_CLOSE);
  }//ends constructor

  public void openFile()throws Exception{
   File f = new File("info.txt");
   if(f.exists()){
    FileReader reader = null;
    try{
     reader = new FileReader("info.txt");
     textArea.read(reader, null);
    } 
    finally{
     if (reader != null){
        reader.close();
     }
    }
   }
  }//ends openFile

  public void actionPerformed(ActionEvent e){
   String text = textArea.getText();
   if(e.getActionCommand().equals("Save & Exit")){

    try{
     BufferedWriter reader = new BufferedWriter(new FileWriter(new File("info.txt"),true));
     reader.write(text);
     reader.newLine();
     reader.close();
    }catch(IOException E){
    System.out.println("the error is " + E);
    }
   }
   System.exit(0);



 } 
}// ends finalA class

Answer 1

因此，根据您的可用代码，您只需在创建 JTextArea 之后，在构造函数末尾调用 openFile 即可。

public TestRead() {
    //...
    textArea.setLineWrap(true);
    textArea.setWrapStyleWord(true);
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    try {
        openFile();
    } catch (IOException exp) {
        exp.printStackTrace();
    }
}//ends constructor

不要使用null布局，像素完美布局在现代GUI设计中是一种幻觉。您无法控制字体规范、DPI 或渲染管道等因素，所有这些因素都可能改变组件的单独要求。

Swing 被设计为使用布局管理器，并且更新界面的许多功能都与其相关。如果您放弃布局管理器，请准备好承受永无休止的工作和挫败感