字符串變量將不顯示是不會在JFrame中

-1

可變String結果不會在JPaneloutpanel顯示，當我運行該程序顯示。有人能告訴我爲什麼嗎？我嘗試過使用Google搜索和static等幾小時試驗，但我相信static不是OO友好的答案，即使它確實解決了它。字符串變量將不顯示是不會在JFrame中

import java.util.*; 
import javax.swing.*; 
import javax.swing.border.EmptyBorder; 
import javax.swing.border.LineBorder; 
import java.awt.*; 
import java.awt.event.*; 

public class AProgram extends JFrame 
      implements WindowListener, ActionListener { 

    public JButton gbt = new JButton("GO"); 
    public JPanel outpanel = new JPanel(); 
    public ArrayList<String> responses; 
    public String result; 

    public AProgram() { 
     super ("Program"); 
    } 

    public void init() { 
     //output 
     outpanel.setOpaque(true); 
     outpanel.setPreferredSize(new Dimension(600, 75)); 
     outpanel.setBorder(new LineBorder(Color.black, 2));  
     JLabel jl = new JLabel();  
     jl.setText(result); 
     outpanel.add(jl); 
     this.add("South", outpanel); 

     //press-button - does NOT sit in a panel. 
     gbt.setBackground(Color.GREEN); 
     gbt.setPreferredSize(new Dimension(75, 75)); 
     gbt.setBorder(new LineBorder(Color.black, 2)); 
     this.add("East", gbt); 

     //all 
     gbt.addActionListener(this); 
     this.addWindowListener(this); 
     this.setLocationRelativeTo(null); 
     this.pack(); 
     this.setVisible(true); 
    } 

    public void actionPerformed (ActionEvent evt) { 
     String input = "A Lion is "; 
     finishSentence(input); 
    } 

    public void windowClosing (WindowEvent e) { 
     this.setVisible(false); 
     this.dispose(); 
    } 

    public void windowOpened(WindowEvent e) {} 
    public void windowClosed(WindowEvent e) {} 
    public void windowIconified(WindowEvent e) {} 
    public void windowDeiconified(WindowEvent e) {} 
    public void windowActivated(WindowEvent e) {} 
    public void windowDeactivated(WindowEvent e) {} 

    public String finishSentence(String inwds) { 
     responses = new ArrayList<String>(); 
     responses.add(0, "a bookish creature"); 
     responses.add(1, "quiet and unassuming"); 
     responses.add(2, "King of the Jungle"); 

     String result = inwds + responses.get(2); 

     return result; 
    } 

    public static void main (String[] args) { 
     AProgram me = new AProgram(); 
     me.init(); 
    } 
}

來源

2014-09-05 user3814983

使用邏輯和一致的代碼格式風格！代碼縮進旨在幫助人們遵循程序流程。 – 2014-09-05 07:56:18

請記住，您可以簡單地使用'frameInstance.setDefaultCloseOperation（JFrame.DISPOSE_ON_CLOSE）'，而不是覆蓋'WindowListener'方法，與'windowClosing（）'方法試圖實現的效果相同。這1行相當於那10行:-) – 2014-09-05 08:12:12

在init()方法設置導致的jl文本是null。

然後在您的actionPerformed()中調用方法finishSentence()，該方法返回String，但您沒有將其分配給任何變量或元素。

再次

呼叫jl.setText()在actionPerformed()

public void actionPerformed (ActionEvent evt) { 

     String input = "A Lion is "; 

     jl.setText(finishSentence(input));           

     }

來源

2014-09-05 05:16:17

：D（以及使我的JLabel classlevel數據）它的工作原理。哦，我的天哪謝謝。我一直堅持這個3小時。！ – user3814983 2014-09-05 05:22:39

如果能幫助解決問題，請[接受]（http://meta.stackexchange.com/a/5235/155831）。我還建議查看您的[早期問題]（http://stackoverflow.com/users/3814983/user3814983?tab=questions）併爲這些問題選擇一個答案。 – 2014-09-05 07:56:49

字符串變量將不顯示是不會在JFrame中

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