使用從文件中讀入的新數據更新JTextArea

Question

我有一個搜索框，用戶可以鍵入一個狀態，它將從關於該州選舉結果的文本文件讀取數據。但是我的JTextArea不顯示新的數據。我進行了調試，並確定數據正在正確讀取。我讀過很多類似於我的問題，但沒有找到解決方案來解決我的特定問題。任何人都可以提供任何建議，我應該如何去做這件事。這是我的代碼。

package view; 

import data.VoteIO; 
import business.State; 
import java.awt.*; 
import java.awt.event.ActionEvent; 
import java.awt.event.ActionListener; 
import javax.swing.*; 
import javax.swing.event.*; 
import java.io.*; 
import java.util.logging.Level; 
import java.util.logging.Logger; 

//illustrate listening for a selection of the JList 
public class Voting2000 extends JFrame implements ActionListener{ 

    private ResultsView votePanel; 
    private Container pane; 
    private JTextField search; 
    private JButton goSearch; 
    private JLabel instructions; 

    public Voting2000() throws IOException{ 
     votePanel = new ResultsView(new State("Nebraska", "NE")); 
     search = new JTextField(); 
     goSearch = new JButton("Search"); 
     instructions = new JLabel("To search for a states input must be in following format State, State's abbreviate for example Nebraska, NE "); 
     pane = getContentPane(); 
     goSearch.addActionListener(this); 
     pane.setLayout(new BorderLayout()); 
     pane.add(BorderLayout.NORTH,instructions); 
     pane.add(BorderLayout.CENTER, votePanel); 
     pane.add(BorderLayout.SOUTH,search); 
     pane.add(BorderLayout.EAST,goSearch); 
     pack(); 
     setVisible(true); 
    } 

    public static void main(String[] args) throws IOException{ 
      Voting2000 listing = new Voting2000(); 
    } 

    public void actionPerformed(ActionEvent e) 
    { 
     String state = search.getText().toLowerCase(); 
     String[] fields = state.split(","); 
     try { 
      State aState = new State(fields[0].trim(),fields[1].trim());; 
      votePanel = new ResultsView(aState); 
      pane.add(BorderLayout.CENTER,votePanel); 
      pane.revalidate(); 
      pane.repaint(); 
     } catch (IOException ex) { 
      Logger.getLogger(Voting2000.class.getName()).log(Level.SEVERE, null, ex); 
     } 
    } 

} 

這裏是

package view; 

import javax.swing.*; 
import java.util.List; 
import business.*; 
import java.awt.event.ActionEvent; 
import java.awt.event.ActionListener; 

/** 
* 
* @author rmildenb 
*/ 
public class ResultsView extends JPanel{ 
    private JTextArea results; 
    private Stats stat; 


    public ResultsView(){ 

     createView(); 
    } 

    public ResultsView(Stats state) { 
     this.stat = state; 
     createView(); 
    } 

    public void createView(){ 
     results = new JTextArea(5, 35); 
     JScrollPane pane = new JScrollPane(results); 
     pane.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_NEVER); 
     this.add(pane); 
     showInformation(); 
    } 

    public void showInformation(){ 
     results.setText(""); 
     results.setText(stat.getDescription()); 
     results.setCaretPosition(0); 

    } 



} 

我試圖從容器窗格中刪除的votePanel它其運作重繪JTextArea是創建ResultsView類，但是當我嘗試添加新我剛剛創建並重新繪製窗格沒有出現。

Answer 1

votePanel = new ResultsView(aState); 

創建新組件不會將組件添加到GUI。組件只是坐在內存中。

而不是創建一個新的ResultsView面板，您應該有一個方法，只需用新文本刷新文本區域。然後文本區域將自動重新繪製。

另一種選擇要複雜得多。該代碼是這樣的：

panel.remove(exisiting ResultsView panel); 
panel.add(new ResultsView panel); 
panel.revalidate(); 
panel.repaint(); 

的重新驗證（）是關鍵，因爲這將調用佈局管理器，這樣所有組件的大小和定位正確。