JLabel沒有更新與計時器

Question

我已經在互聯網上搜索試圖找到如何使一個自動更新時鐘gui程序沒有運氣。我嘗試了許多不同的方法，並以相同的結果結束。我正在使用swing Timer，因爲我已經讀過這是處理gui的最好方法。我嘗試過驗證（），重新驗證（），repaint（）。 下面是部分代碼：

import javax.swing.*; 
//import java.awt.event.*; 
import java.util.*; 
import javax.swing.Timer; 
import java.awt.event.ActionEvent; 
import java.awt.event.ActionListener; 

public class ClockPanel extends JPanel { 
    Calendar now = Calendar.getInstance(); 
    int hour = now.get(Calendar.HOUR_OF_DAY); 
    int minute = now.get(Calendar.MINUTE); 
    int second = now.get(Calendar.SECOND); 
    int month = now.get(Calendar.MONTH) + 1; 
    int day = now.get(Calendar.DAY_OF_MONTH); 
    int year = now.get(Calendar.YEAR); 

    private String currentTime; 
    private JLabel current; 

    public ClockPanel() { 
     super(); 
     currentTime = getTime(); 
     current = new JLabel(currentTime); 
     add(current); 

     ActionListener updater = new ActionListener() { 
      @Override 
      public void actionPerformed(ActionEvent event) { 
       getTime(); 
       if(second == 60){ 
        current.setText(currentTime); 
        revalidate(); 

       } 
       getTime(); 
      } 
     }; 
     Timer timer = new Timer(1000, updater); 
     timer.start(); 
    } 

這是我結束了最後的代碼;我知道這是錯誤的，但我已經改變了這麼多好幾個小時，我放棄了。由於

編輯：這裏是你調用getTime()代碼

public String getTime() { 
     String time; 
     String period = "AM"; 
     String monthName = ""; 
     switch(month) { 
      case (1): 
       monthName = "January"; 
       break; 
      case (2): 
       monthName = "February"; 
       break; 
      case (3): 
       monthName = "March"; 
       break; 
      case (4): 
       monthName = "April"; 
       break; 
      case (5): 
       monthName = "May"; 
       break; 
      case (6): 
       monthName = "June"; 
       break; 
      case (7): 
       monthName = "July"; 
       break; 
      case (8): 
       monthName = "August"; 
       break; 
      case (9): 
       monthName = "September"; 
       break; 
      case (10): 
       monthName = "October"; 
       break; 
      case (11): 
       monthName = "November"; 
       break; 
      case (12): 
       monthName = "December"; 
       break; 
     } 
     if(hour >= 12){ 
      period = "PM"; 
     } 
     time = monthName + " " + day + ", " + year + " " 
       + hourCheck(hour) + ":" + minuteCheck(minute) + period; 
     return time; 
    } 

    private int hourCheck(int hour) { 
     if(hour > 12){ 
      hour -= 12; 
      return hour; 
     } 
     if(hour == 0) { 
      hour += 12; 
      return hour; 
     } 
     return hour; 
    } 

    private StringBuilder minuteCheck(int minute) { 
     StringBuilder time = new StringBuilder(); 

     if(minute < 10) { 
      return time.append("0").append(minute); 
     } 
     else { 
      time.append("").append(minute); 
     } 
     return time; 
    } 

} 

Answer 1

的休息，但忽略了它所返回。當前時間保持原來的狀態。替換爲您的代碼：

ActionListener updater = new ActionListener() { 
     @Override 
     public void actionPerformed(ActionEvent event) { 
      String newTime = getTime(); 
      current.setText(newTime); 
     } 
    }; 

編輯：

你不僅忽略getTime()返回的值，但也getTime()總是返回同樣的事情，因爲你總是重用月，分，秒等已經被初始化了一次，當面板被構建時。你不使用標準的DateFormat類也會讓你的生活變得非常困難。

從面板除了一個JLabel這樣刪除的所有字段，並更改getTime()方法的東西：

private String getTime() { 
    // get the CURRENT date: 
    Date currentDate = new Date(); 

    // format it and return it: 
    return new SimpleDateFormat("MMMM dd, yyyy hh:mm a").format(currentDate); 
} 

Answer 2

你可以調整你的代碼，這和它的工作：

public class ClockPanel extends JPanel { 
    private final JLabel current; 

    public ClockPanel() { 
     current = new JLabel(now()); 
     add(current); 

     new Timer (1000, new ActionListener() { 
      @Override 
      public void actionPerformed(ActionEvent event) { 
       current.setText(now()); 
      } 
     }).start(); 
    } 

    private static String now() { 
     // implement your own 
     return new Date().toString(); 
    } 

    public static void main(String[] args) { 
     JFrame main = new JFrame("Simple Clock"); 
     main.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     main.setSize(200, 200); 
     main.setContentPane(new ClockPanel()); 
     main.setVisible(true); 
    } 
}