Question

我想要的是，当用户点击按钮时，在Textbox或JList中输入的数据或从任何地方删除的数据都会进入数组列表。

我不想建立数据库！我只想在用户使用应用程序时存储数据。我已经尝试了一切，但似乎事件按钮需要一定的难度，代码不应该被认真对待，它只是用于分析。

重要的是只需按一下按钮就可以将数据写入数组。例如：

btnSaveToArray.addActionListener (new ActionListener () {

    public void actionPerformed (ActionEvent e) {

        ArrayList recordArray=new ArrayList(); 

        // This variable receiveList, receives value a given selected from a JList, is far from good.
        String receiveList = userList.getSelectedValue().toString();
        // The variable recordArray capture this value, the goal is that this variable store it.
        recordArray.add(receiveList); 

        // these two lines to see if I recorded the same roof but're angry, it just returns me one record element.
        System.out.println(recordArray.toString()); 
        // these two lines to see if I recorded the same roof but're angry, it just returns me one record element.
        System.out.println(recordArray.size());   
    }

我尝试打印出数组的内容，看是否记录了用户输入，但是没有打印出来。

Answer 1

代码的问题是，只要用户单击“确定”按钮，就会执行actionPerformed（ActionEvent）方法。每次调用该方法时，您都要创建一个ArrayList，它不包含以前的选择。因此，ArrayList必须是一个实例变量。每次用户单击“确定”按钮时，只需将选择添加到列表中即可。

Answer 2

您需要在ActionListener

之外保留List

  ArrayList recordArray=new ArrayList(); 

  btnSaveToArray.addActionListener (new ActionListener () {

        public void actionPerformed (ActionEvent e) {

        String receiveList = userList.getSelectedValue().toString();  

        recordArray.add(receiveList); 

        System.out.println(recordArray.toString()); 
        System.out.println(recordArray.size());  
  }

Answer 3

您应该在动作侦听器之外建立arraylist，并且只在侦听器内执行add函数，如下所示：

public class Recorder {

    public ArrayList recordArray;

    public Recorder() {
        recordArray = new ArrayList();
        JButton btnSaveToArray = new JButton.... //whatever you are doing here
        btnSaveToArray.addActionListener (new ActionListener () {
            public void actionPerformed (ActionEvent e) {
                String receiveList = userList.getSelectedValue().toString();
                recordArray.add(receiveList);
                showTheRecords();
        });
    }

    public void showTheRecords() {
        for (int i = 0; i < recordArray.size(); i++ ) {
            System.out.println(recordArray.get(i).toString()); //get 
        }
        System.out.println("Record count: " + recordArray.size());
    }

}

使用JButton JAVA将数据写入ArrayList

3 个答案: