在swing中聲明的運行方法.Jframe類

Question

我創建了兩個swing.JFrame s。 登錄GUI和用戶GUI。我要的是當它切換到登錄GUI用戶圖形界面，存在一種需要改變爲("you're logged in as" + username);

我user JFrame的源代碼嘗試這種代碼的用戶界面一Jlabel。

`loggedInAsLable.setText("you're logged in as" + username);` 

的方法

，這就是所謂的用戶jframe主要方法。但由於某些原因 它不起作用。

當Jframe變得可見時，我該如何運行一些方法？

public class CustomerServiceOfficerUI extends javax.swing.JFrame { 

private static Statement st; 
ResultSet rs; 
Connection con = null; 
Login loginUI = new Login(); // gets current user Id 
Employee cso = new CustomerServiceOfficer(); //creates new customer service officer object 

/** 
* Creates new form CustomerServiceOfficer 
*/ 
public CustomerServiceOfficerUI() { 
    initComponents(); 
} 

public void getCSOdetails() { 

    try { 
     Class.forName("com.mysql.jdbc.Driver"); 

     con = DriverManager.getConnection("jdbc:mysql://localhost:3306/flyingcarsdb", "root", ""); 
     System.out.println("database connected"); 

    } catch (ClassNotFoundException | SQLException ex) { 
     System.out.println("Error: " + ex); 
    } 

    try { 
     // Retrieve customer service officer details 
     st = con.createStatement(); 
     String query = "select * FROM customerserviceofficer WHERE Id = '" + loginUI.getCurrentUserId() + "'"; 

     rs = st.executeQuery(query); 

     while (rs.next()) { 
      //Assign the details with setters 
      cso.setFname(rs.getString("Fname")); 
      cso.setEmail(rs.getString("Email")); 
     } 

    } catch (Exception ex) { 
     System.out.println("Error : " + ex); 
    } 
loggedInAsLable.setText("you're logged in as : " + cso.getId()); 
//this is where LABLE is changed, 'cso.getId()' returns the user ID 
    } 

Answer 1

如果你真的需要變爲可見時更新您的JFrame（如你的最後一句話建議），則可以使用的WindowListener的打電話給你getCSODetails（）方法。我已經包含了三個激活事件 - 打開，激活和去鈍化;您可以刪除其中的任何一項，以便將更新限制爲適合您需求的特定事件。如果您只需在窗口打開後更新標籤，請刪除方法windowDeiconified()和windowActivated()。 但是，請注意，getCSODetails（）方法設計得相當糟糕，每當窗口變得可見/重點時調用它都會導致性能損失，並且GUI的響應性將受到數據庫性能的嚴重影響。我猜你所顯示的客戶信息在登錄會話期間沒有改變，所以最好執行一次查詢，緩存詳細信息，然後從緩存中顯示出來。

Answer 2

試試這個：

public class CustomerServiceOfficerUI extends javax.swing.JFrame { 

    private static Statement st; 
    ResultSet rs; 
    Connection con = null; 
    Login loginUI = new Login(); // gets current user Id 
    Employee cso = new CustomerServiceOfficer(); //creates new customer service officer object 

    /** 
    * Creates new form CustomerServiceOfficer 
    */ 
    public CustomerServiceOfficerUI() { 
     initComponents(); 
    } 

    public void getCSOdetails() { 

     try { 
      Class.forName("com.mysql.jdbc.Driver"); 

      con = DriverManager.getConnection("jdbc:mysql://localhost:3306/flyingcarsdb", "root", ""); 
      System.out.println("database connected"); 




      // Retrieve customer service officer details 
      st = con.createStatement(); 
      String query = "select * FROM customerserviceofficer WHERE Id = '" + loginUI.getCurrentUserId() + "'"; 

      rs = st.executeQuery(query); 

      while (rs.next()) { 
       //Assign the details with setters 
       cso.setFname(rs.getString("Fname")); 
       cso.setEmail(rs.getString("Email")); 
      } 

SwingUtilities.invokeLater(new Runnable() 
     { 

      public void run() 
      { 
       loggedInAsLable.setText("you're logged in as : " + cso.getId()); 
       loggedInAsLable.repaint(); 

      } 
     }); 

     } catch (Throwable ex) { 
      System.out.println("Error : " + ex); 
SwingUtilities.invokeLater(new Runnable() 
     { 

      public void run() 
      { 
       loggedInAsLable.setText("There is a problem with your code : " + ex); 
       loggedInAsLable.repaint(); 

      } 
     }); 

     } finally { 

     } 
    //this is where LABLE is changed, 'cso.getId()' returns the user ID 
     }