此应用程序从文本文件中提取数据并将其插入JTable
。如果文件发生更改并重新加载数据,则附加Observer
以检查每300毫秒。我的setChanged()
课程中有notifyObservers()
和Observer
。
当数据添加到表格中时,getRowCount()
报告已添加该行,通知程序正在运行。事实上,除了repaint()
之外,一切正常。我试过revalidate()
和fireTableDataChanged()
都无济于事。我将不胜感激。整个过程中都没有报告编译错误。
表格型号
package HardwareDbFile;
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.InputStreamReader;
import java.util.StringTokenizer;
import java.util.Vector;
import javax.swing.table.AbstractTableModel;
public class HardwareFileTableModel extends AbstractTableModel{
protected Vector data;
protected Vector columnNames ;
protected String datafile;
public HardwareFileTableModel(String file){
datafile = file;
initVectors();
}
public void initVectors() {
String aLine ;
data = new Vector();
columnNames = new Vector();
try {
FileInputStream fin = new FileInputStream(datafile);
try (BufferedReader br = new BufferedReader(new InputStreamReader(fin))) {
StringTokenizer st1 = new StringTokenizer(br.readLine(), "|");
while(st1.hasMoreTokens()) {
columnNames.addElement(st1.nextToken());
}
// extract data
while ((aLine = br.readLine()) != null) {
StringTokenizer st2 = new StringTokenizer(aLine, "|");
while(st2.hasMoreTokens()) {
data.addElement(st2.nextToken());
}
}
}
}
catch (Exception e) {
e.printStackTrace();
}
}
@Override
public int getRowCount() {
return data.size() / getColumnCount();
}
@Override
public int getColumnCount(){
return columnNames.size();
}
@Override
public String getColumnName(int columnIndex) {
String colName = "";
if (columnIndex <= getColumnCount()) {
colName = (String)columnNames.elementAt(columnIndex);
}
return colName;
}
@Override
public Class getColumnClass(int columnIndex){
return String.class;
}
@Override
public boolean isCellEditable(int rowIndex, int columnIndex) {
return false;
}
public Object getValueAt(int rowIndex, int columnIndex) {
return (String)data.elementAt( (rowIndex * getColumnCount()) + columnIndex);
}
public void setValueAt(Object aValue, int rowIndex, int columnIndex) {
}
}
观察员类
package HardwareDbFile;
import java.awt.event.*;
import java.io.*;
import java.util.*;
import javax.swing.Timer;
public class HardwareFileObserver extends Observable implements ActionListener {
Timer time = new Timer(300,this); // check every 300ms
long lastModified;
String file ;
HardwareFileObserver (String string) {
file = string;
File f = new File(file);
lastModified = f.lastModified(); // original timestamp
time.start();
}
@Override
public void actionPerformed(ActionEvent e) {
File f = new File(file);
long actualLastModified = f.lastModified();
if (lastModified != actualLastModified) {
// the file have changed
lastModified = actualLastModified;
setChanged();
notifyObservers();
}
}
}
主类
public class HardwareInventoryUI extends javax.swing.JFrame implements Observer {
private String datafile = "hardware.dat";
private String dataFilePath = "C:\\Windows\\Temp\\hardware.dat";
protected HardwareFileTableModel model;
/**
* Creates new form HardwareInventoryUI
*/
public HardwareInventoryUI() {
initComponents();
model = new HardwareFileTableModel(dataFilePath);
HardwareFileObserver fileWD;
// this Observable object is monitoring any file change
fileWD = new HardwareFileObserver(dataFilePath);
fileWD.addObserver(this);
}
@Override
public void update(Observable o, Object arg) {
// reload data because data file have changed
model.initVectors();
jTable.repaint();
}
添加记录按钮
private void jAddRecordActionPerformed(java.awt.event.ActionEvent evt) {
String toolID = jToolID.getText();
String toolName = jToolName.getText();
String quantity = jQuantity.getText();
String itemPrice = jItemPrice.getText();
try {
model = new HardwareFileTableModel(dataFilePath);
FileWriter fstream = new FileWriter(dataFilePath, true);
try (BufferedWriter newRecord = new BufferedWriter(fstream)) {
newRecord.newLine();
newRecord.write(toolID + "|"+ toolName + "|" + quantity + "|" + itemPrice );
}
} catch (IOException ex) {
Logger.getLogger(HardwareInventoryUI.class.getName()).log(Level.SEVERE, null, ex);
}
}
答案 0 :(得分:2)
您的TableModel
应该实施Observer
,而不是您的观点。在update()
方法中,更新data
和fireTableDataChanged()
。 JTable
会收听TableModel
并自动更新。
还要考虑提到here的观察者模式的替代实现。
如图所示here,您setValueAt()
的实施不正确。您需要触发将通知监听表的事件:
@Override
public void setValueAt(Object value, int row, int column) {
// update data
fireTableCellUpdated(row, column);
}
如果您datafile
的内容可以作为命令的标准输出获取,则可以使用概述here的方法消除该文件。
附录:正如@kleopatra所评论的那样,“请注意,对于一个表现良好的模型,你永远不需要对视图更新进行任何思考,它们只是自动神奇地发生:-)或者反过来:如果手动重新绘制一个视图(例如表,树,列表)似乎是一个解决方案,模型实现是不正确的。“