当用户按下按钮“加载文件”时，我在 JFrame 中设置了这个方法；但是，当用户第二次按下按钮时。. . 他们在第一个表格下方获得了另一个表格，因此所有信息都被复制，并且超出了我的“不可调整大小”框架。
无论用户按下按钮多少次，我怎样才能让它只加载一张桌子？
JButton btnLoad = new JButton("Load File")
private void GetAction()
{
ActionHandler handler = new ActionHandler();
btnLoad.addActionListener(handler);
}
private class ActionHandler implements ActionListener
{
public void actionPerformed(ActionEvent evt)
{
String incmd = evt.getActionCommand();
if (incmd.equals("Load File")) // If Load File button is pressed
DatabaseLoad();
else if (incmd.equals("Exit")) // If Exit button is pressed
System.exit(0);
}
}
private void DatabaseLoad()
{
try
{
// The driver allows you to query the database with Java
// forName dynamically loads the class for you
Class.forName("com.mysql.jdbc.Driver");
// DriverManager is used to handle a set of JDBC drivers
// getConnection establishes a connection to the database
// You must also pass the userid and password for the database
String url = "jdbc:mysql://localhost:3306/charity";
conn = DriverManager.getConnection (url,"root","password");
// Statement objects executes a SQL query
// createStatement returns a Statement object
Statement sqlState = conn.createStatement();
// This is the query I'm sending to the database
String selectStuff = "SELECT `name`, `charity`, `amount` FROM `charity`.`donations` ";
// A ResultSet contains a table of data representing the
// results of the query. It can not be changed and can
// only be read in one direction
rows = sqlState.executeQuery(selectStuff);
// Temporarily holds the row results
Object[] tempRow;
// next is used to iterate through the results of a query
while(rows.next()){
// Gets the column values based on class type expected
tempRow = new Object[]{rows.getString(1), rows.getString(2), rows.getDouble(3) };
// Adds the row of data to the end of the model
dTableModel.addRow(tempRow);
}
// Successfully loaded, message the user
message1.setText("<html><font color='red'>Database Info Loaded</font>");
message2.setText("");
}
catch (SQLException ex)
{
// String describing the error
System.out.println("SQLException: " + ex.getMessage());
// Vendor specific error code
System.out.println("VendorError: " + ex.getErrorCode());
}
catch (ClassNotFoundException e)
{
// Executes if the driver can't be found
System.out.println("Driver Cannot be found");
e.printStackTrace();
}
// Create a JTable using the custom DefaultTableModel
JTable table = new JTable(dTableModel);
// Increase the font size for the cells in the table
table.setFont(new Font("Serif", Font.PLAIN, 16));
// Increase the size of the cells to allow for bigger fonts
table.setRowHeight(table.getRowHeight()+5);
// Allows the user to sort the data
table.setAutoCreateRowSorter(true);
// right justify amount column
TableColumn tc = table.getColumn("amount");
RightTableCellRenderer rightRenderer = new RightTableCellRenderer();
tc.setCellRenderer(rightRenderer);
// Disable auto resizing
table.setAutoResizeMode(JTable.AUTO_RESIZE_OFF);
// Set the width for the columns
TableColumn col1 = table.getColumnModel().getColumn(0);
col1.setPreferredWidth(200);
TableColumn col2 = table.getColumnModel().getColumn(1);
col2.setPreferredWidth(275);
TableColumn col3 = table.getColumnModel().getColumn(2);
col3.setPreferredWidth(75);
// Put the table in a scrollpane and add scrollpane to the frame
JScrollPane scrollPane = new JScrollPane(table);
scrollPane.setPreferredSize(new Dimension(552, 400));
this.add(scrollPane, BorderLayout.CENTER);
}
// To change justification to the right
class RightTableCellRenderer extends DefaultTableCellRenderer {
public RightTableCellRenderer() {
setHorizontalAlignment(JLabel.RIGHT);
}
}