ArrayList的JComboBoxes

Question

的我創建的JComboBox

private static ArrayList<JComboBox> comboList = new ArrayList<>(); 

的ArrayList，然後加入JComboBox每個實例的ArrayList

private void courseUnit() { 
     String[] units = {"6", "5", "4", "3", "2", "1"}; 
     int x = 520, y = 30; 
     for (int i = 0; i < 10; i++) { 
      comboUnits = new JComboBox<>(units); 
      comboUnits.setBounds(x, y, 100, 25); 
      y += 30; 
      comboUnits.setToolTipText("Select course unit"); 
      comboUnits.setVisible(true); 
      comboUnits.addActionListener(new PaneAction()); 
      add(comboUnits); 
      comboList.add(comboUnits); //comboUnits added to ArrayList 
     } 
    } 

我的問題是，我如何得到每個組合框的selectedItem屬性因爲我試過這個ArrayList

//this is supposed to get the selected item of the first ComboBox and assign to courseGrade[0] 
    public void actionPerformed(ActionEvent evt) { 
      String[] courseGrade = new String[10]; 
      courseGrade[0] = (String)comboList.get(0).getSelectedItem(); 

and the pr圖沒有編譯。

Answer 1

可以應重視ActionListner，而你所添加的JComboBox到ArrayList

private void courseUnit() { 
      String[] units = {"6", "5", "4", "3", "2", "1"}; 
      int x = 520, y = 30; 
      for (int i = 0; i < 10; i++) { 
       comboUnits = new JComboBox<>(units); 
       comboUnits.setBounds(x, y, 100, 25); 
       y += 30; 
       comboUnits.setToolTipText("Select course unit"); 
       comboUnits.setVisible(true); 
       //comboUnits.addActionListener(new PaneAction()); 
       add(comboUnits); 

//////////////// Here are the changes 

       comboUnits.addActionListener (new ActionListener() { 
        public void actionPerformed(ActionEvent e) { 
         String selectedItem = (String)e.getSelectedItem(); 
        } 
       }); 
       comboList.add(comboUnits); //comboUnits added to ArrayList 
      } 
     } 

Answer 2

我終於得到它。我不得不創建ArrayList的一個靜態實例變量

private static ArrayList<JComboBox> comboList; 

，然後實例化，它在構造函數中

comboList = new ArrayList<>(); 

新courseUnit（）方法現在看起來是這樣

private void courseUnit() { 
     String[] units = {"6", "5", "4", "3", "2", "1"}; 
     int x = 520, y = 30; 
     for (int i = 0; i < 10; i++) { 
      comboUnits = new JComboBox<>(units); 
      comboUnits.setBounds(x, y, 100, 25); 
      comboUnits.setToolTipText("Select course unit"); 
      y += 30; 
      comboUnits.setVisible(true); 
      add(comboUnits); 
      //I added ActionListener to each comboBox in the ArrayList, 
      //thanks to Junaid for this 
      comboUnits.addActionListener(new ActionListener(){ 
       public void actionPerformed(ActionEvent evt){  
        ArrayList<String> courseGrade = new ArrayList<>(); 
        JComboBox comboBox = (JComboBox) evt.getSource(); 
        courseGrade.add((String) comboBox.getSelectedItem()); 
       } 
      }); 
      comboList.add(comboUnits); 
     }//end of loop 
    } //end of method