The ActionListener interface is found in java.awt.event package.It has only one method: actionPerformed().
If you implement the ActionListener class, you need to follow 3 steps. It is the shorthand way, so you do not need to follow the 3 steps. For more visit training.javatpoint.com Course Fee: 6000 Only Duration: 6 Week -- Javatpoint Services JavaTpoint offers too many high quality services. Website Designing Website Development Java Development PHP Development WordPress Graphic Designing Logo Digital Marketing On Page and Off Page SEO PPC Content Development Corporate Training Classroom and Online Training Data Entry Training For College Campus JavaTpoint offers college campus training on Core Java, Advance Java,.Net, Android, Hadoop, PHP, Web Technology and Python. What is not clear to me after studying your article is to define who is the Listener and who is sender of the EventObject in this case. The program decides either to ignore or to respond to when such cases happen. Click Listener Java Code That IsFor example, if we want to do something when a user clicks a button, then we need to identify 3 things: (1) the button itself, (2) the event when the button is clicked, and (3) the responding code that is interested in the button-clicked event (called listener). When such the event happens, the listener that is interested in that ActionEvent, which is called ActionListener, contains the method (called handler ) to be invoked. Again, Java pre-defines this handler method as actionPerformed(ActionEvent e). It was possible because the ActionListener had been registered to listen to the ActionEvent by the button. The corresponding listener interface is ActionListener (with the handler method actionPerformed(ActionEvent e) ), and ItemListener (with the handler itemStateChanged(ItemEvent e) ). A Component (JTextArea, or JLabel) can fire MouseEvent or KeyEvent when the user has pressed, clicked, moved, exited mouse, pressed or typed key onfrom that component. Corresponding listener interface is MouseLister (which defines several handlers, such as mousePressed(MouseEvent e), and mouseEntered(MouseEvent e) ), and KeyListener (with pre-defined handlers). But we want to define our own because it is better suited with our application. For example, a bank account can fire a custom event BalanceEvent when the customer widthraws too much from hisher account. For our custom BalanceListener s handler balanceViolated(BalanceEvent e) responds appropriately, it should be able to know how much the current balance is, the minimum amount that the account holder to maintain, and the date and time of that attempted transaction. That means the BalanceEvent contains the data needed for the handler. This is not possible with pre-defined Java event-listener pairs. Click Listener Java Full And CannotWhen a certain condition happends (such as low balance on the bank account, or a biology class is full and cannot take more students), the source object invokes the handler(s) method on its listeners. Since we pass the XEvent object to these handler(s), the handler(s) can respond appropriately. For example, informing the client code the current balance, attempted ammount to widraw on what date. Max speed is temporarily set to 60MPH, min speed 40, and the default 50 when the car starts driving on the highway. It calls each handler of each SpeedListener object in the speedListenerList, to notify and do something about that event. Its up to the client code to implement the concrete handler(s). Thanks for that. There are two questions, which are not clear to me after having studied your article in detail for a couple of days. I do not fully understand, what is the benefit to add additional values into the SpeedEvent class Since the source is a reference to the class, I thought you could reference to those variables maxspeed and minspeed easily via e.getSource(), right I think adding copies of these variables into the SpeedEvent class means data redundancy. I would be really thankful, if you could explain once again its purpose. Suppose using Swing for the GUI. Imagine there is a JPanel for the acquisition of some data from the user. I am trying implementation of design pattern MVC in a simplified form, since Swing itself is combining View and Controller also. Click Listener Java Update The EnteredI thought that once the data is entered by the user a custom event is fired to all listeners, to let them read and update the entered data.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |