處理JFileChooser窗口關閉？

Question

我有一個創建如圖所示一個JFileChooser：

JFileChooser chooser = new JFileChooser(); 
int choosen = chooser.showOpenDialog(fileSelector.this); 

if (choosen == JFileChooser.CANCEL_OPTION) { 
    System.out.println("Closed"); 
} 

如果我關閉了窗口進行選擇我的錯誤：

Exception in thread "main" java.lang.NullPointerException 
    at fileSelector.fileSelector(fileSelector.java:32) 
    at createAndControl.main(createAndControl.java:15) 

我想知道正確的方法處理這個問題，我應該在窗口關閉時採取什麼行動來避免這種情況？

TIA

Answer 1

我們建議這樣做反過來：

public static void main(String[] args) { 
    SwingUtilities.invokeLater(new Runnable() { 

     @Override 
     public void run() { 
      JFileChooser fc = new JFileChooser(); 
      int returnVal = fc.showOpenDialog(null); 

      if (returnVal == JFileChooser.APPROVE_OPTION) { 
       File file = fc.getSelectedFile(); 
       //This is where a real application would open the file. 
       System.out.println("Opening: " + file.getName() + ".\n"); 
      } else { 
       System.out.println("Open command cancelled by user.\n"); 
      } 
     } 
    }); 
}