i have a question regarding a program i am working on. It`s a database manager for a MqSQL db , written in Java. So i have the following program structure.
So i have a main class that extends JFrame, whichh is the main frame of the interface, like this (removed the unecessary code not relevant to the discussion) :
public class MainInterface extends JFrame {
public MainInterface {
................
MainInterface.setLayout(new FlowLayout());
MainInterface.setVisible(true);
TopToolbar toolbar;
try {
toolbar = new TopToolbar();
MainInterface.add(toolbar);
ResultsPanel Results = new ResultsPanel();
MainInterface.add(Results);
} catch (IOException e) {
e.printStackTrace();
}
}
TopToolbar and ResultsPanel are 2 other classes that extend JPanel, the TopToolbar class having a JToolBar with buttonsadded to it (Move Forward, MoveBack, Add entry)
public class TopToolbar extends JPanel implements ActionListener {
TopToolBar()
{
//constructor in which i was adding button to the toolbar, not relevat
}
}
public void actionPerformed(ActionEvent e) {
String cmd = e.getActionCommand();
if (MoveFirst.equals(cmd)){
try {
DatabaseAccess disp = new DatabaseAccess();
disp.getResults();
int id = disp.return_id();
System.out.println(id);
} catch (//exceptions) {
e1.printStackTrace();
}
}
That is the ActionListener event for the next button, which should trigger reading the next entry in the db
DatabaseAccess is another class with initializes the DB connection , and has these 2 methods :
public void getResults() throws SQLException {
Connection con = (Connection) DriverManager.getConnection(URL, user, "")
sql = (Statement) con.createStatement();
result_set = sql.executeQuery("select * from persons");
while (result_set.next()) {
id = result_set.getInt(1);
name = result_set.getString(2);
}
}
public int return_id(){
return id;
}
The return_ID method returns (and it does work) the ID (first key in the database, will obviously add methods for the rest of the entries in the db). Now i want to show the ID in the final JPanel, the one called ResultsSet (just 3 JLabels and 3 TextFields for the ID , Name etc., in a GridLayout).
Since the dababase class creation (and subsequently the methods forr reading the db and returning the result) is done inside the ActionPerformed method inside the TopToolBar Jpanel, i can`t access it from the MainInterface JFrame and then use something like
ResultsPanel DispResults = new ResultsPanel();
add(DispResults);
DispResults.setID(id_Value)
where setID would be a method in the ResultsPanel that uses the JTextBox setText to set the text .
Hoope i`ve managed to explain my issue as clear as i can.
JFrame, apart from locking your into a single use case, making it impossible to re-use you UI in other ways, you're not adding any new functionality to the frame. Have a look at 5 Reasons to Use Composition over Inheritance in Java and OOP as s starting point for more details