jquckbox上的actionListener

Question

我想添加一個匿名actionListener到JCheckBox，但有一些困難訪問我想更新值的對象。我不斷收到關於非最終的錯誤，然後當我將它們改爲最終時，它會抱怨其他事情。
什麼即時試圖做的是下面（我已經刪除了一些GUI代碼，使其更易於閱讀）：

for (FunctionDataObject fdo : wdo.getFunctionDataList()) 
{ 
    JLabel inputTypesLabel = new JLabel("Input Types: "); 
    inputsBox.add(inputTypesLabel); 
    for (int i = 0; i < fdo.getNumberOfInputs(); i++) 
    { 
     JLabel inputLabel = new JLabel(fdo.getInputNames().get(i)); 
     JComboBox inputTypeComboBox = new JComboBox(getTypes()); 
     inputTypeComboBox.addActionListener(new ActionListener() { 
      public void actionPerformed(ActionEvent e) 
      { 
       fdo.getInputTypes().set(i, (String) inputTypeComboBox.getSelectedItem()); 
      } 
     }); 
    } 
}  

Answer 1

您無法訪問匿名類中的非最終變量。可以略微修改代碼來解決這個限制（我已經fdo和inputTypeComboBox決賽，我也做的i終稿）：

for (final FunctionDataObject fdo : wdo.getFunctionDataList()) { 
     JLabel inputTypesLabel = new JLabel("Input Types: "); 
     inputsBox.add(inputTypesLabel); 
     for (int i = 0; i < fdo.getNumberOfInputs(); i++) { 
      final int final_i = i; 
      JLabel inputLabel = new JLabel(fdo.getInputNames().get(i)); 
      final JComboBox inputTypeComboBox = new JComboBox(getTypes()); 
      inputTypeComboBox.addActionListener(new ActionListener() { 
       public void actionPerformed(ActionEvent e) { 
        fdo.getInputTypes().set(final_i, (String) inputTypeComboBox.getSelectedItem()); 
       } 
      }); 
     } 
    } 

Answer 2

更新您的代碼

inputTypeComboBox.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent e) 
     { 
      fdo.getInputTypes().set(i, (String) inputTypeComboBox.getSelectedItem()); 
     } 
    }); 

到

final counter = i; 
final JComboBox inputTypeComboBox = new JComboBox(getTypes()); 
final FunctionDataObject finalFDO = fdo; 
inputTypeComboBox.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent e) 
     { 
      finalFDO.getInputTypes().set(counter, (String) inputTypeComboBox.getSelectedItem()); 
     } 
    }); 

This鏈接解釋了爲什麼您只能訪問內部類中的最終變量

Answer 3

這將工作：

for (final FunctionDataObject fdo : wdo.getFunctionDataList()) { 
     JLabel inputTypesLabel = new JLabel("Input Types: "); 
     inputsBox.add(inputTypesLabel); 
     for (int i = 0; i < fdo.getNumberOfInputs(); i++) { 
      JLabel inputLabel = new JLabel(fdo.getInputNames().get(i)); 
      final JComboBox inputTypeComboBox = new JComboBox(getTypes()); 
      final int index = i; 
      inputTypeComboBox.addActionListener(new ActionListener() { 
       public void actionPerformed(ActionEvent e) { 
        fdo.getInputTypes().set(index, (String) inputTypeComboBox.getSelectedItem()); 
       } 
      }); 
     } 
    }