我正在用java创建一个没有数据库的库系统程序.(直接用文件).
我在jtable中删除一行(从文件中删除)也有一个奇怪的问题.
有时当我在表格中选择一行并单击删除按钮时,更多的一行已被删除！
也是大多数时候它正常工作!!
我的代码：
public final class UserPage extends JFrame implements ActionListener {
private AllUser userModel;
private JTable uTable;
JButton deleteUser;
int selectedRow;
public UserPage() {
titleUserCount();
userModel = new AllUser();
uTable = new JTable(userModel);
add(new JScrollPane(uTable), BorderLayout.CENTER);
add(buttonPanels(), BorderLayout.PAGE_START);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setSize(800, 600);
this.setLocation(300, 60);
this.setResizable(false);
}
public final JPanel buttonPanels() {
JPanel buttonsPanel = new JPanel(new FlowLayout(FlowLayout.LEFT));
deleteUser = new JButton("Delete User");
deleteUser.addActionListener(this);
buttonsPanel.add(deleteUser);
return buttonsPanel;
}
public void titleUserCount() {
AllUser userCount = new AllUser();
UserPage.this.setTitle("All User Information , Number Of user is : " + userCount.getRowCount());
}
@Override
public void actionPerformed(ActionEvent e) {
if (e.getSource() == deleteUser) {
int selectedrow = uTable.getSelectedRow();
if (selectedrow >= 0) {
userModel.RemoveRow(selectedrow);
titleUserCount();
} else {
JOptionPane.showMessageDialog(null, "No Row Selected");
}
}
}
}
我的模特课：
public class AllUser extends AbstractTableModel {
UserInformation uiS = new UserInformation();
String[] col = {"ID", "Fname", "Lname", "Gender", "Date"};
ArrayList<UserInformation> Udata = new ArrayList<UserInformation>();
public AllUser() {
BufferedReader br = null;
try {
FileReader fr = new FileReader("AllUserRecords.txt");
br = new BufferedReader(fr);
String line;
while ((line = br.readLine()) != null) {
if (line.trim().length() == 0) {
continue;
}
Udata.add(initializeUserInfos(line));
}
} catch (IOException e) {
} finally {
if (br != null) {
try {
br.close();
} catch (IOException ioe) {
}
}
}
}
private UserInformation initializeUserInfos(String str) {
UserInformation Uinit = new UserInformation();
String[] CellArray = str.split(" ");
Uinit.setID(CellArray[0]);
Uinit.setFname(CellArray[1]);
Uinit.setLname(CellArray[2]);
Uinit.setGender(CellArray[3]);
Uinit.setDate(CellArray[4]);
return Uinit;
}
public void RemoveRow(int rowIndex) {
if (RemoveUserFromFile(rowIndex)) {
Udata.remove(rowIndex);
fireTableRowsDeleted(rowIndex, rowIndex);
} else {
JOptionPane.showMessageDialog(null, "Unable to delete");
}
}
public boolean RemoveUserFromFile(int index) {
File Mf = new File("AllUserRecords.txt");
File Tf = new File("Uoutput.txt");
try {
BufferedReader Ubr = new BufferedReader(new FileReader(Mf));
PrintWriter Upw = new PrintWriter(new FileWriter(Tf));
String line;
while ((line = Ubr.readLine()) != null) {
if (line.trim().length() == 0) {
continue;
}
if (!line.startsWith(String.valueOf(getValueAt(index, 0)))) {
Upw.println(line);
}
}
Upw.close();
Ubr.close();
Mf.delete();
Tf.renameTo(Mf);
return true;
} catch (FileNotFoundException e1) {
return false;
} catch (IOException ioe) {
return false;
}
}
@Override
public String getColumnName(int colu) {
return col[colu];
}
@Override
public int getRowCount() {
return Udata.size();
}
@Override
public int getColumnCount() {
return col.length;
}
@Override
public Object getValueAt(int rowIndex, int columnIndex) {
UserInformation uinfoS = Udata.get(rowIndex);
Object value = null;
switch (columnIndex) {
case 0:
value = uinfoS.getID();
break;
case 1:
value = uinfoS.getFname();
break;
case 2:
value = uinfoS.getLname();
break;
case 3:
value = uinfoS.getGender();
break;
case 4:
value = uinfoS.getDate();
break;
default:
value = "...";
}
return value;
}
@Override
public void setValueAt(Object value, int rowIndex, int columnIndex) {
UserInformation userInfo = Udata.get(rowIndex);
switch (columnIndex) {
case 0:
userInfo.setID((String) value);
break;
case 1:
userInfo.setFname((String) value);
break;
case 2:
userInfo.setLname((String) value);
break;
case 3:
userInfo.setGender((String) value);
break;
case 4:
userInfo.setDate((String) value);
break;
}
}
}
用户信息类：
public class UserInformation {
private String Fname;
private String Lname;
private String ID;
private String Gender;
private String Date;
public String getFname() {
return Fname;
}
public void setFname(String fname) {
this.Fname = fname;
}
public String getLname() {
return Lname;
}
public void setLname(String lname) {
this.Lname = lname;
}
public String getID() {
return ID;
}
public void setID(String i_d) {
this.ID = i_d;
}
public String getGender() {
return Gender;
}
public void setGender(String gndr) {
this.Gender = gndr;
}
public String getDate() {
return Date;
}
public void setDate(String date) {
this.Date = date;
}
@Override
public String toString() {
return ID + " " + Fname + " "
+ Lname + " " + Gender + " " + Date + "\n";
}
}
我的文字文件：
85 lo ii Female 2013/03/08
86 jkj nmn Female 2013/03/08
52 tyr fgfg Female 2013/03/08
7 dfdf wew Female 2013/03/08
47 zczc asa Female 2013/03/08
16 erw www Male 2013/03/08
83 gfg dsd Male 2013/03/08
解决方法:
好吧,既然我没有你的所有代码,所以我正在进行一个虚拟程序,用于从JTable中删除记录以及相应的文件.观察MyTabeModel类中定义的removeRow方法.它还涵盖了从ArrayList删除记录后无法将数据写入文件(records.temp)的风险.
import javax.swing.table.*;
import java.awt.event.*;
import java.awt.*;
import javax.swing.*;
import java.util.*;
import java.io.*;
public class TableFocus extends JFrame
{
MyTableModel model1;
JTable table1;
public void createAndShowGUI()
{
setTitle("JTables");
Container c = getContentPane();
model1 = new MyTableModel();
table1 = new JTable(model1);
table1.setColumnSelectionAllowed(false);
table1.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
JScrollPane jsTable1 = new JScrollPane(table1);
c.add(jsTable1);
JButton button = new JButton("Delete");
button.addActionListener( new ActionListener()
{
public void actionPerformed(ActionEvent evt)
{
if (model1.getRowCount() > 0 && table1.getSelectedRow() != -1 )
{
model1.deleteRow(table1.getSelectedRow());
}
}
});
add(button,BorderLayout.SOUTH);
setSize(500,300);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setVisible(true);
}
private class MyTableModel extends AbstractTableModel
{
String columns[] ;
ArrayList<ArrayList<String>> data;
public MyTableModel()
{
columns = new String[] {"Roll No.","Name"};
prepareData();
}
private void prepareData()
{
data = new ArrayList<ArrayList<String>>();
data.add(new ArrayList<String>(){{add("1");add("Michael");}});
data.add(new ArrayList<String>(){{add("2");add("Derake");}});
data.add(new ArrayList<String>(){{add("3");add("Archie");}});
}
@Override
public String getColumnName(int columnIndex)
{
return columns[columnIndex];
}
@Override
public int getRowCount()
{
return data.size();
}
@Override
public int getColumnCount()
{
return columns.length;
}
@Override
public Object getValueAt(int row, int col)
{
return data.get(row).get(col);
}
@Override
public void setValueAt(Object aValue, int rowIndex, int colIndex)
{
data.get(rowIndex).set(colIndex,(String)aValue);
fireTableCellUpdated(rowIndex,colIndex);
}
@Override
public boolean isCellEditable(int row, int col)
{
return false;
}
public void deleteRow(int row)
{
ArrayList<String> temp = data.get(row);//backup of value in case of IOException while writing to file
BufferedWriter bfr = null;
try
{
data.remove(row);
//Write here the logic for repopulating file with new records.
bfr = new BufferedWriter(new OutputStreamWriter(new FileOutputStream("records.temp")));
StringBuffer sBuffer = new StringBuffer();
for (ArrayList<String> list : data)
{
StringBuffer buf = new StringBuffer();
for (String val : list )
{
buf.append(val+"\t");
}
buf.replace(buf.length() - 1, buf.length(),"\n");
sBuffer.append(buf.toString());
}
bfr.write(sBuffer.toString());
bfr.flush();
bfr.close();
fireTableRowsDeleted(row,row);
}
catch (Exception ex)
{
data.add(row,temp);//Rollback the delete from ArrayList
ex.printStackTrace();
}
finally
{
if (bfr != null)
{
try
{
bfr.close();
}
catch (Exception ex){}
}
}
}
}
public static void main(String[] args)
{
SwingUtilities.invokeLater( new Runnable()
{
@Override
public void run()
{
TableFocus ths = new TableFocus();
ths.createAndShowGUI();
}
});
}
}
UPDATE
Sometimes when i select a row in my table and click to delete button,
more that one line has been deleted!
在完成您的代码之后,我了解了删除多行的情况.情况是：如果文件中有多行,则从您要删除的记录的相同用户ID开始.
例如,假设您的文件中有这样的条目：
85 lo ii Female 2013/03/08
86 jkj nmn Female 2013/03/08
52 tyr fgfg Female 2013/03/08
86 jkj pqr Male 2013/03/08
7 dfdf wew Female 2013/03/08
47 zczc asa Female 2013/03/08
16 erw www Male 2013/03/08
83 gfg dsd Male 2013/03/08
这里userID 86包含在两行中(第2行和第4行).当您在JTable中选择第4行以删除该特定记录时,它会从您的文件中删除第2行和第4行.但在JTable中,第二行将继续显示,因为直到现在它都没有使用新文件刷新.只要用新文件刷新JTable,它就会显示从那里删除的行.
要知道它为什么会发生,请看看你的RemoveUserFromFile(int index)方法while循环,如下所示：
while ((line = Ubr.readLine()) != null) //Reads the file till the end.
{
if (line.trim().length() == 0) {
continue;
}
if (!line.startsWith(String.valueOf(getValueAt(index, 0)))) //If line starts with 86 don't write it to new `Uoutput.txt`. so all lines starting with 86 will be ignored.
{
Upw.println(line);//Lines starting with 86 is not written.
}
}
我希望你现在有充分的理由知道为什么有时从JTable中删除一条记录会从你的文件中删除两行或两行以上.
解决此问题的方法是以下列方式更改方法(RemoveRow和RemoveUserFromFile):(使用此修改后的代码)
public void RemoveRow(int rowIndex) {
UserInformation temp = Udata.get(rowIndex);//Keep it as back up so that you could reconsolidate it to ArrayList in case RemoveUserFromFile return false
Udata.remove(rowIndex);//remove the element from Udata on temporary basis.
if (RemoveUserFromFile(rowIndex))
{
fireTableRowsDeleted(rowIndex, rowIndex);
}
else
{
Udata.add(rowIndex,temp);//re-insert temp in ArrayList as the file updation is failed.
JOptionPane.showMessageDialog(null, "Unable to delete");
}
}
public boolean RemoveUserFromFile(int index)
{
File Mf = new File("AllUserRecords.txt");
File Tf = new File("Uoutput.txt");
PrintWriter Upw = null;
try
{
Upw = new PrintWriter(new FileWriter(Tf));
for (UserInformation uino : Udata )
{
Upw.print(uino.toString());//Don't use Upw.println because the toString() method of UserInformation class is already using \n in last.
}
Upw.close();
Mf.delete();
Tf.renameTo(Mf);
return true;
} catch (FileNotFoundException e1) {
return false;
} catch (IOException ioe) {
return false;
}
finally
{
if (Upw != null)
{
try
{
Upw.close();
}
catch (Exception ex){}
}
}
}
我希望现在能解决你的问题……
注意：作为旁注.我想建议你在编写代码时坚持使用java命名约定.例如：类名始终以大写字母开头.变量名称始终以小写字母开头.常数(即最终变量)的所有字母都是大写的.还有很多其他的.看看oracle的official site.
标签：java,swing,jtable 来源： https://codeday.me/bug/20190715/1468681.html
本站声明： 1. iCode9 技术分享网（下文简称本站）提供的所有内容，仅供技术学习、探讨和分享； 2. 关于本站的所有留言、评论、转载及引用，纯属内容发起人的个人观点，与本站观点和立场无关； 3. 关于本站的所有言论和文字，纯属内容发起人的个人观点，与本站观点和立场无关； 4. 本站文章均是网友提供，不完全保证技术分享内容的完整性、准确性、时效性、风险性和版权归属；如您发现该文章侵犯了您的权益，可联系我们第一时间进行删除； 5. 本站为非盈利性的个人网站，所有内容不会用来进行牟利，也不会利用任何形式的广告来间接获益，纯粹是为了广大技术爱好者提供技术内容和技术思想的分享性交流网站。