爲什麼只有windowGainedFocus（）不起作用？

Question

我有下面的代碼，在那裏我一個的WindowListener添加到我的JFrame，我想覆蓋的方法windowGainedFocus：

final JFrame jd = new JFrame(); 
    jd.setLocationRelativeTo(null); 
    jd.setSize(300, 425); 
    jd.setLayout(null); 
    jd.setResizable(false); 

    jd.addWindowListener(new WindowAdapter() { 
     public void windowGainedFocus(WindowEvent windowEvent){ 
       System.out.println("TEST"); 
     }   
    }); 

但它不工作，當我關注這個框架不打印「測試」。 但是，當我覆蓋的方法windowClosing它的工作原理：

jd.addWindowListener(new WindowAdapter() { 
     public void windowClosing(WindowEvent windowEvent){ 
       System.out.println("TEST"); 
     }   
    }); 

什麼是與windowGainedFocus()問題？

Answer 1

jd.addWindowListener(new WindowAdapter() { 
    public void windowGainedFocus(WindowEvent windowEvent){ 
      System.out.println("TEST"); 
    }   
}); 

應該是：

jd.addWindowFocusListener(new WindowAdapter() { 
    public void windowGainedFocus(WindowEvent windowEvent){ 
      System.out.println("TEST"); 
    }   
}); 

我知道有一個很好的理由我討厭適配器類..我會建議使用監聽器，而不是適配器。