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Event Handling - Coggle Diagram

- - - - Foreground Event
        
        require direct interaction of the user.
        
        generated as consequences of a person interacting with the GUI components.
        
        Exp: Click on abutton, Moving mouse, Entering characters through keyboard
      - Background Event
        
        events may occur without interactions with a user interface.
        
        Exp: Operation completed, Timer expires
- - - - Event Object
        
        the change in state in the event source class
        
        interacting with the graphical interfaces: Click a button. Entering text
        
        Contains two methods: getSource( ) and toString( ).
      - Event Listener
        (Event Handler)
        
        generating a response to an event
        
        received an event then process and returns the result
        
        Event handling requires:
        
        Event handler class
        
        // Define an inner class to handle the "Count" button-click
        private class BtnCountListener implements ActionListener {
        }
        
        Register Instance
        
        //Register listener
        BtnCountListener listener = new BtnCountListener();
        btnCount.addActionListener(listener);
        
        Implements Method
        
        // Event handler method - Called back upon button-click
        public void actionPerformed(ActionEvent evt) {
        ++count;
        tfCount.setText(count + "");
      - Event Source
        
        An object that generates an event
        
        A source must register listeners in order for the listeners to receive notifications about a specific type of event
  - - - // Constructor to setup GUI components and event handlers public AWTCounter() { setLayout(new FlowLayout()); // sets its layout to FlowLayout to arrange lblCount = new Label("Counter"); // construct the Label component add(lblCount); // Frame container adds Label component tfCount = new TextField(count + "", 10); // construct the TextField component with initial text tfCount.setEditable(false); // set to read-only add(tfCount); // Frame container adds TextField component btnCount = new Button("Count"); // construct the Button component add(btnCount); // Frame container adds Button component }
    - - // Define an inner class to handle the "Count" button-click private class BtnCountListener implements ActionListener { // Event handler method - Called back upon button-click. public void actionPerformed(ActionEvent evt) { ++count; // Increase the counter value tfCount.setText(count + ""); // Convert int to String &Display the counter value on the TextField tfCount }
    - - //Register listener BtnCountListener listener = new BtnCountListener(); btnCount.addActionListener(listener); setTitle("AWT Counter"); // sets its title setSize(300, 100); // sets its initial window size setVisible(true); // Frame shows