如何使用JFileChooser保存/打开对象的ArrayList？

Question

好的，我是Java编程的新手，并且我不太了解文件读取/写入的概念。 我尝试查看有关Files的docs.oracle网页，但是考虑到我要尝试的内容有所不同，它们发现它们并没有真正的帮助。

我有以下3个文件：CVolunteer，CDialog和TestDialog。 CVolunteer创建并反对一个可以自愿辅导学生的人。 CDialog管理志愿者的添加/编辑。 TestDialog显示志愿者的JList，并允许用户编辑，添加，删除或清除列表。 我让这3个类正常运行，并将在下面显示它们（很抱歉，它们很长！）。

这是我需要的帮助...我在主窗口中添加了两个按钮：“保存”和“打开”。 用户可以随时保存当前的JList志愿者。 单击“保存”后，将弹出一个JFileChooser窗口，并要求用户提供一个文件名，所有志愿者对象将保存在该文件名中。 当用户单击“打开”时，应弹出另一个JFileChooser窗口，并询问用户要打开的文件。 当前在主窗口中的志愿者将被删除，所选文件中的志愿者将代替他们。 我不确定是否需要使用序列化...。

如果有人可以帮助解释如何完成此操作或帮助我编写代码来处理“保存” /“打开”事件，我将非常感谢！ 提前致谢：）

我相信唯一需要更改的文件是TestDialog，我还包括了其他文件，以防有人想要运行它

***很抱歉，如果有任何缩进错误，我必须在此对话框CVolunteer.java中手动完成所有操作

public class CVolunteer {
    int volNum;
    String name;
    int sub, volDays, trans;

    public CVolunteer(int vNum, String vName, int subj, int days, int needTrans){
        volNum = vNum;
        name = vName;
        sub = subj;
        volDays = days;
        trans = needTrans;
    }

    private String subjectToString()
    {
        switch (sub){
        case 0: 
            return "Math";
        case 1:
            return "Science";
        case 2:
            return "English";
        case 3:
            return "History";
        }

        return " ";
    }

    private String volDaysToString()
    {
        String str = "";
        str +=((volDays&1)!=0)?"M":"-";
        str +=((volDays&2)!=0)?"T":"-";
        str +=((volDays&4)!=0)?"W":"-";
        str +=((volDays&8)!=0)?"R":"-";

        return str;
    }

    private String transToString()
    {
        switch(trans)
        {
        case 0:
            return "Yes";
        case 1:
            return "No";
        }

        return " ";
    }

    public String getVolunteerLine()
    {
        return String.format("%05d                      %-30s%-30s%-30s%s", 
                volNum, name, subjectToString(), volDaysToString(), transToString());
    }

}

CDialog.java

import java.awt.Container;
import java.awt.event.*;
import javax.swing.*; 


public class CDialog extends JDialog implements ActionListener
{
    private JLabel label1;
    private JLabel lNum;
    private JLabel label2;
    private JTextField tfName;

    private JLabel label3;
    private ButtonGroup  subGroup;
    private JRadioButton rbMath;
    private JRadioButton rbScience;
    private JRadioButton rbEnglish;
    private JRadioButton rbHistory;

    private JLabel label4;
    private JCheckBox cbMonday;
    private JCheckBox cbTuesday;
    private JCheckBox cbWednesday;
    private JCheckBox cbThursday;

    private JLabel label5;
    private ButtonGroup transGroup;
    private JRadioButton rbYes;
    private JRadioButton rbNo;

    private JButton okButton = null;
    private JButton cancelButton = null;

    private boolean cancelled = true;
    public boolean isCancelled() {return cancelled;}

    private CVolunteer answer;
    public CVolunteer getAnswer() {return answer;}

    public CDialog(JFrame owner, String title, CVolunteer vol)
    {
        super(owner, title, true);

        Container c = getContentPane();
        c.setLayout(null);

        label1 = new JLabel ("Volunteer Number:");
        label1.setSize(140,20);
        label1.setLocation(40,40);
        c.add(label1);

        lNum = new JLabel(String.format("%05d", vol.volNum));
        lNum.setSize(40,20);
        lNum.setLocation(150,40);
        c.add(lNum);

        label2 = new JLabel ("Volunteer Name: ");
        label2.setSize(100,20);
        label2.setLocation(40,90);
        c.add(label2);

        tfName = new JTextField(vol.name);
        tfName.setSize(120,20);
        tfName.setLocation(140,90);
        c.add(tfName);

        int x,y;
        int w,h;
        x=4;
        y=150;
        w=180;
        h=20;

        label3 = new JLabel("Subject: ");
        label3.setSize(85,13);
        label3.setLocation(x,y);
        c.add(label3);

        rbMath = new JRadioButton("Math", vol.sub==0);
        rbMath.setSize(w,h);
        rbMath.setLocation(x+16,y+30);
        c.add(rbMath);

        rbScience = new JRadioButton("Science", vol.sub==1);
        rbScience.setSize(w,h);
        rbScience.setLocation(x+16,y+66);
        c.add(rbScience);

        rbEnglish = new JRadioButton("English", vol.sub==2);
        rbEnglish.setSize(w,h);
        rbEnglish.setLocation(x+16,y+102);
        c.add(rbEnglish);

        rbHistory = new JRadioButton("History", vol.sub==3);
        rbHistory.setSize(w,h);
        rbHistory.setLocation(x+16,y+138);
        c.add(rbHistory);

        subGroup = new ButtonGroup();
        subGroup.add(rbMath);
        subGroup.add(rbScience);
        subGroup.add(rbEnglish);
        subGroup.add(rbHistory);

        x=220;
        y=150;
        w=120;
        h=20;
        label4 = new JLabel("Days Available: ");
        label4.setSize(w,h);
        label4.setLocation(x,y);
        c.add(label4);

        cbMonday = new JCheckBox("Monday (M)", (vol.volDays&1)!=0);
        cbMonday.setSize(w,h);
        cbMonday.setLocation(x+6,y+30);
        c.add(cbMonday);

        cbTuesday = new JCheckBox("Tuesday (T)", (vol.volDays&2)!=0);
        cbTuesday.setSize(w,h);
        cbTuesday.setLocation(x+6,y+66);
        c.add(cbTuesday);

        cbWednesday = new JCheckBox("Wednesday (W)", (vol.volDays&4)!=0);
        cbWednesday.setSize(w,h);
        cbWednesday.setLocation(x+6,y+102);
        c.add(cbWednesday);

        cbThursday = new JCheckBox("Thursday (R)", (vol.volDays&8)!=0);
        cbThursday.setSize(w,h);
        cbThursday.setLocation(x+6,y+138);
        c.add(cbThursday);

        x=480;
        y=150;
        w=180;
        h=20;
        label5 = new JLabel("Need Transport? :");
        label5.setSize(150,13);
        label5.setLocation(x,y);
        c.add(label5);

        rbYes = new JRadioButton("Yes", vol.trans==0);
        rbYes.setSize(w,h);
        rbYes.setLocation(x+12,y+30);
        c.add(rbYes);

        rbNo = new JRadioButton("No", vol.trans==1);
        rbNo.setSize(w,h);
        rbNo.setLocation(x+12,y+66);
        c.add(rbNo);

        transGroup = new ButtonGroup(); 
        transGroup.add(rbYes);
        transGroup.add(rbNo);

        cancelButton = new JButton("Cancel");
        cancelButton.addActionListener(this);
        cancelButton.setSize(100,50);
        cancelButton.setLocation(116,380);
        c.add(cancelButton);

        okButton = new JButton("OK");
        okButton.addActionListener(this);
        okButton.setSize(100,50);
        okButton.setLocation(400,380);
        c.add(okButton);

        setSize(700,480);
        setLocationRelativeTo(owner);
        setVisible(true);







    }


    public void actionPerformed(ActionEvent e) 
    {
        if (e.getSource()==okButton) {
            int num=Integer.parseInt(lNum.getText());

            String name=tfName.getText();

            int subj=-1;
            if (rbMath.isSelected()) subj = 0;
            if (rbScience.isSelected()) subj = 1;
            if (rbEnglish.isSelected()) subj = 2;
            if (rbHistory.isSelected()) subj = 3;

            int days=0;
            if (cbMonday.isSelected()) days |= 1;
            if (cbTuesday.isSelected()) days |= 2;
            if (cbWednesday.isSelected()) days |= 4;
            if (cbThursday.isSelected()) days |= 8;

            int tran=0;
            if (rbYes.isSelected()) tran = 0;
            if (rbNo.isSelected()) tran = 1;

            answer=new CVolunteer(num, name, subj, days, tran);

            cancelled = false;
            setVisible(false);
        }
        else if(e.getSource()==cancelButton) {
            cancelled = true;
            setVisible(false);
        }

    }


}

TestDialog.java

import java.awt.event.*;

import javax.swing.*;

import java.awt.*;
import java.io.*;
import java.util.ArrayList;


public class TestDialog extends JFrame implements ActionListener
{
    JLabel  myLabel1  = null;
    JLabel  myLabel2  = null;
    JLabel  myLabel3  = null;
    JLabel  myLabel4  = null;
    JLabel  myLabel5  = null;
    JLabel  myLabel6  = null;

    File fileName = new File("Volunteers.txt");

    ArrayList<CVolunteer> volArray;
    private DefaultListModel volunteers;
    JList volList;
    JScrollPane scrollPane = null;

    JButton bAdd = null;
    JButton bEdit = null;
    JButton bRemove = null;
    JButton bClear = null;
    JButton bSave = null;
    JButton bOpen = null;

    int volNumb;

    public TestDialog()
    {
        super("Volunteer Info");

        Container c = getContentPane();
        c.setLayout(null);

        myLabel1 = new JLabel("Vol Number");
        myLabel1.setSize(200,50);
        myLabel1.setLocation(100,10);
        c.add(myLabel1);

        myLabel2 = new JLabel("Vol Name");
        myLabel2.setSize( 200, 50 );
        myLabel2.setLocation( 200, 10 );
        c.add(myLabel2);

        myLabel3 = new JLabel("Subject");
        myLabel3.setSize( 200, 50 );
        myLabel3.setLocation( 310, 10);
        c.add(myLabel3);

        myLabel4 = new JLabel("Vol Days");
        myLabel4.setSize( 200, 50 );
        myLabel4.setLocation( 400, 10 );
        c.add(myLabel4);

        myLabel5 = new JLabel("Transport");
        myLabel5.setSize( 200, 50 );
        myLabel5.setLocation( 500, 10 );
        c.add(myLabel5);

        volArray = new ArrayList<CVolunteer>();
        volunteers = new DefaultListModel();
        volList = new JList(volunteers);
        volList.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);

        scrollPane = new JScrollPane(volList);
        scrollPane.setSize(500,300);
        scrollPane.setLocation(100,50);
        c.add(scrollPane);

        bAdd = new JButton("Add");
        bAdd.setSize( 100, 50 );
        bAdd.setLocation( 20, 400 );
        bAdd.addActionListener(this);
        c.add(bAdd);

        bEdit = new JButton("Edit");
        bEdit.setSize( 100, 50 );
        bEdit.setLocation( 150, 400 );
        bEdit.addActionListener(this);
        c.add(bEdit);

        bRemove = new JButton("Remove");
        bRemove.setSize( 100, 50 );
        bRemove.setLocation( 280, 400 );
        bRemove.addActionListener(this);
        c.add(bRemove);

        bClear = new JButton("Clear");
        bClear.setSize( 100, 50 );
        bClear.setLocation( 410, 400 );
        bClear.addActionListener(this);
        c.add(bClear);

        bSave = new JButton("Save");
        bSave.setSize( 100, 50 );
        bSave.setLocation( 540, 400 );
        bSave.addActionListener(this);
        c.add(bSave);

        bOpen = new JButton("Open");
        bOpen.setSize( 100, 50 );
        bOpen.setLocation( 670, 400 );
        bOpen.addActionListener(this);
        c.add(bOpen);

        setSize( 800, 600 );
        setLocation( 100, 100 );
        setVisible(true);

        volNumb = 0;

    }

    public void actionPerformed(ActionEvent e) {
        if(e.getSource()==bAdd) {
            volNumb++;
            CVolunteer defaultVol = new CVolunteer(volNumb, "", 1, 0, 0); 
            CDialog dialogWnd = new CDialog(this, "Add a Volunteer", defaultVol);
            if (!dialogWnd.isCancelled()) {
                volArray.add(dialogWnd.getAnswer());
                volunteers.addElement(dialogWnd.getAnswer().getVolunteerLine());
                volList.setSelectedIndex(volunteers.size()-1);
                volList.ensureIndexIsVisible(volunteers.size()-1);
            }
        }
        else if(e.getSource()==bEdit) {
            int index=volList.getSelectedIndex();
            if (index>=0) {
                CDialog dialogWnd = new CDialog (this, "Edit a Volunteer", volArray.get(index));
                if (!dialogWnd.isCancelled()) {
                    volArray.set(index, dialogWnd.getAnswer());
                    volunteers.set(index, dialogWnd.getAnswer().getVolunteerLine());
                }
            }
        }
        else if(e.getSource()==bRemove) {
            int index=volList.getSelectedIndex();
            if (index>=0) {
                volArray.remove(index);
                volunteers.remove(index);
                if (volunteers.size()>0) {
                    if (index==volunteers.size()) {
                        index--;
                        }
                    volList.setSelectedIndex(index);
                    volList.ensureIndexIsVisible(index);
                }
            }
        }
        else if(e.getSource()==bClear) {
            volArray.clear();
            volunteers.clear();
        }

        else if (e.getSource()==bSave)
        {

            //my sorry attempt at writing a file.. ignore this!
            try {
                FileWriter fw = new FileWriter(fileName);
                Writer output = new BufferedWriter(fw);
                int size = volArray.size();
                for (int i = 0; i<size; i++)
                {
                    output.write(volArray.get(i).getVolunteerLine() + "\n");
                }
                output.close();
            } 
            catch (Exception e1) {
                // TODO Auto-generated catch block

            }
            final JFileChooser fc = new JFileChooser();

        }

        else if (e.getSource()==bOpen)
        {

        }
    }

    public static void main(String[] args) {
        TestDialog mainWnd = new TestDialog();
    }


}

编辑：

这是我的“保存”按钮的一些尝试代码。...我仍然不知道它是否在正确的轨道上！ 它似乎什么也没做

else if (e.getSource()==bSave)
    {

        try 
        {
            FileOutputStream fileOut = new FileOutputStream("???");
            ObjectOutputStream out = new ObjectOutputStream(fileOut);
            for(int i=0; i<volArray.size(); i++)
            {
                out.writeObject(volArray.get(i).getVolunteerLine());

            }
            out.close();
            fileOut.close();

        } catch (Exception e1) {
            // TODO Auto-generated catch block

        }
        final JFileChooser fc = new JFileChooser();

    }

Answer 1

您必须使用定义的特定格式来写入文件：在志愿者类中添加序列化方法，然后可以遍历它们并序列化它们中的每一个。 字符串serialize（）会将所有成员编码为字符串，然后可以在读取时（在Open上）进行重构。

一个示例可以是用逗号分隔的列表：member1 = xxx，member2 = xxx，...或xml或json更加方便:)

在阅读时，情况恰恰相反，解析文件的内容并重新建立志愿者！

编辑：

Saving:
Open a file in write mode
write all your n volunteers
at this point you should have n lines in your file
close the file

Reading:
Open your file in reading mode
Read it line by line
For each line
 split over ','
 build your volunteer
 add it to volArray
close your file

这对您有意义吗？ 通过简单的Google搜索，这些步骤都很简单

编辑：最终JFileChooser fc =新的JFileChooser（）;

if (returnVal == JFileChooser.APPROVE_OPTION) {
  File file = fc.getSelectedFile();
  //This is where a real application would open the file.
  log.append("Opening: " + file.getName() + "." + newline);
  // Here you can open the file and write to it

  //



} else {
  log.append("Open command cancelled by user." + newline);
}

打开时可以执行相同的操作，选择文件然后从中读取