摇摆：JTable直到在任何地方单击鼠标都不会更新？

Question

Simply I am writing application code that interacts with database (MySQL). I made everything OK in Swing to work with database.

Refresh code:
Finally I wrote some code to refresh the data in the JTable to reflect the actual data from the database.

This is useful in a scenario like this. If I added a new record to JTable, generally this record will be added to the underlying database. But if I added a record that duplicates an existing one, the underlying database will not insert it, but it will be displayed in the JTable (which has no corresponding record in real database).

The code to refresh has the job to get the new data from the database. It work OK but it doesn't affect (update/refresh) the table until I click the mouse anywhere within the JTable.

How to make a swing component update correctly without poking it.

Answer 1

"But if I added a record that duplicates an existing one, the underlying database will not insert it, but it will be displayed in the JTable... How to make a swing component update correctly without poking it?"

• PreparedStatemnt#executeUpdate() - returns an int , the number of rows updated in the database.

With that said, you could check if the result is 0. If it isn't, then add the row to the table only if the insert is successful. Something like this

String text1 = textfield1.getText();
String text2 = textfield2.getText();
String text3 = textfield3.getText();

PreparedStatement ps = conn.prepareStatement("INSERT into table1 values (?, ?, ?)");
ps.setString(1, text1);
ps.setString(2, text2);
ps.setString(3, text3);

int result = ps.executeUpdate();    // check for rows affected

if (result != 0 ) {                 // only if result != 0 do we update the table
    DefaultTableModel model = (DefaultTableModel)jTable.getModel();
    Object[] row = { text1, text2, text3 };
    model.addRow(row);
} else {
    someStatusLabel.setText("That record already exists in the Database");
}

Answer 2

How to make a swing component update correctly without poking it.

1. update the TableModel directly with the changes
2. make sure the updates to the model are done on the Event Dispatch Thread.

Your code to access the database should be done on a non EDT thread so you don't prevent the GUI from responding to events. So you should probably be using a SwingWorker for this code. Then you publish the results so the model can be updated on the EDT.

Read the section from the Swing tutorial on Concurrency for more information.