MouseEvent.MOUSE_ENTERED has the following syntax.
public static final int MOUSE_ENTERED
In the following code shows how to use MouseEvent.MOUSE_ENTERED field.
// w w w. j a v a2 s . c om /* * Copyright (c) 2000 David Flanagan. All rights reserved. * This code is from the book Java Examples in a Nutshell, 2nd Edition. * It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied. * You may study, use, and modify it for any non-commercial purpose. * You may distribute it non-commercially as long as you retain this notice. * For a commercial use license, or to purchase the book (recommended), * visit http://www.davidflanagan.com/javaexamples2. */ import java.awt.AWTEvent; import java.awt.BorderLayout; import java.awt.Dimension; import java.awt.Graphics; import java.awt.event.ComponentEvent; import java.awt.event.FocusEvent; import java.awt.event.InputEvent; import java.awt.event.KeyEvent; import java.awt.event.MouseEvent; import java.awt.event.WindowAdapter; import java.awt.event.WindowEvent; import java.util.Vector; import javax.swing.JFrame; import javax.swing.JPanel; /** A program that displays all the event that occur in its window */ public class Main extends JPanel { /** The constructor: register the event types we are interested in */ public Main() { // We're interested in all types of events this.enableEvents(AWTEvent.MOUSE_EVENT_MASK | AWTEvent.MOUSE_MOTION_EVENT_MASK | AWTEvent.KEY_EVENT_MASK | AWTEvent.FOCUS_EVENT_MASK | AWTEvent.COMPONENT_EVENT_MASK | AWTEvent.WINDOW_EVENT_MASK); this.setPreferredSize(new Dimension(500, 400)); } /** * Display mouse events that don't involve mouse motion. The mousemods() * method prints modifiers, and is defined below. The other methods return * additional information about the mouse event. showLine() displays a line * of text in the window. It is defined at the end of this class, along with * the paintComponent() method. */ public void processMouseEvent(MouseEvent e) { String type = null; switch (e.getID()) { case MouseEvent.MOUSE_PRESSED: type = "MOUSE_PRESSED"; break; case MouseEvent.MOUSE_RELEASED: type = "MOUSE_RELEASED"; break; case MouseEvent.MOUSE_CLICKED: type = "MOUSE_CLICKED"; break; case MouseEvent.MOUSE_ENTERED: type = "MOUSE_ENTERED"; break; case MouseEvent.MOUSE_EXITED: type = "MOUSE_EXITED"; break; } showLine(mousemods(e) + type + ": [" + e.getX() + "," + e.getY() + "] " + "num clicks = " + e.getClickCount() + (e.isPopupTrigger() ? "; is popup trigger" : "")); // When the mouse enters the component, request keyboard focus so // we can receive and respond to keyboard events if (e.getID() == MouseEvent.MOUSE_ENTERED) requestFocus(); } /** * Display mouse moved and dragged mouse event. Note that MouseEvent is the * only event type that has two methods, two EventListener interfaces and * two adapter classes to handle two distinct categories of events. Also, as * seen in init(), mouse motion events must be requested separately from * other mouse event types. */ public void processMouseMotionEvent(MouseEvent e) { String type = null; switch (e.getID()) { case MouseEvent.MOUSE_MOVED: type = "MOUSE_MOVED"; break; case MouseEvent.MOUSE_DRAGGED: type = "MOUSE_DRAGGED"; break; } showLine(mousemods(e) + type + ": [" + e.getX() + "," + e.getY() + "] " + "num clicks = " + e.getClickCount() + (e.isPopupTrigger() ? "; is popup trigger" : "")); } /** * Return a string representation of the modifiers for a MouseEvent. Note * that the methods called here are inherited from InputEvent. */ protected String mousemods(MouseEvent e) { int mods = e.getModifiers(); String s = ""; if (e.isShiftDown()) s += "Shift "; if (e.isControlDown()) s += "Ctrl "; if ((mods & InputEvent.BUTTON1_MASK) != 0) s += "Button 1 "; if ((mods & InputEvent.BUTTON2_MASK) != 0) s += "Button 2 "; if ((mods & InputEvent.BUTTON3_MASK) != 0) s += "Button 3 "; return s; } /** * Display keyboard events. * * Note that there are three distinct types of key events, and that key * events are reported by key code and/or Unicode character. KEY_PRESSED and * KEY_RELEASED events are generated for all key strokes. KEY_TYPED events * are only generated when a key stroke produces a Unicode character; these * events do not report a key code. If isActionKey() returns true, then the * key event reports only a key code, because the key that was pressed or * released (such as a function key) has no corresponding Unicode character. * Key codes can be interpreted by using the many VK_ constants defined by * the KeyEvent class, or they can be converted to strings using the static * getKeyText() method as we do here. */ public void processKeyEvent(KeyEvent e) { String eventtype, modifiers, code, character; switch (e.getID()) { case KeyEvent.KEY_PRESSED: eventtype = "KEY_PRESSED"; break; case KeyEvent.KEY_RELEASED: eventtype = "KEY_RELEASED"; break; case KeyEvent.KEY_TYPED: eventtype = "KEY_TYPED"; break; default: eventtype = "UNKNOWN"; } // Convert the list of modifier keys to a string modifiers = KeyEvent.getKeyModifiersText(e.getModifiers()); // Get string and numeric versions of the key code, if any. if (e.getID() == KeyEvent.KEY_TYPED) code = ""; else code = "Code=" + KeyEvent.getKeyText(e.getKeyCode()) + " (" + e.getKeyCode() + ")"; // Get string and numeric versions of the Unicode character, if any. if (e.isActionKey()) character = ""; else character = "Character=" + e.getKeyChar() + " (Unicode=" + ((int) e.getKeyChar()) + ")"; // Display it all. showLine(eventtype + ": " + modifiers + " " + code + " " + character); } /** * Display keyboard focus events. Focus can be permanently gained or lost, * or temporarily transferred to or from a component. */ public void processFocusEvent(FocusEvent e) { if (e.getID() == FocusEvent.FOCUS_GAINED) showLine("FOCUS_GAINED" + (e.isTemporary() ? " (temporary)" : "")); else showLine("FOCUS_LOST" + (e.isTemporary() ? " (temporary)" : "")); } /** Display Component events. */ public void processComponentEvent(ComponentEvent e) { switch (e.getID()) { case ComponentEvent.COMPONENT_MOVED: showLine("COMPONENT_MOVED"); break; case ComponentEvent.COMPONENT_RESIZED: showLine("COMPONENT_RESIZED"); break; case ComponentEvent.COMPONENT_HIDDEN: showLine("COMPONENT_HIDDEN"); break; case ComponentEvent.COMPONENT_SHOWN: showLine("COMPONENT_SHOWN"); break; } } /** Display Window events. Note the special handling of WINDOW_CLOSING */ public void processWindowEvent(WindowEvent e) { switch (e.getID()) { case WindowEvent.WINDOW_OPENED: showLine("WINDOW_OPENED"); break; case WindowEvent.WINDOW_CLOSED: showLine("WINDOW_CLOSED"); break; case WindowEvent.WINDOW_CLOSING: showLine("WINDOW_CLOSING"); break; case WindowEvent.WINDOW_ICONIFIED: showLine("WINDOW_ICONIFIED"); break; case WindowEvent.WINDOW_DEICONIFIED: showLine("WINDOW_DEICONIFIED"); break; case WindowEvent.WINDOW_ACTIVATED: showLine("WINDOW_ACTIVATED"); break; case WindowEvent.WINDOW_DEACTIVATED: showLine("WINDOW_DEACTIVATED"); break; } // If the user requested a window close, quit the program. // But first display a message, force it to be visible, and make // sure the user has time to read it. if (e.getID() == WindowEvent.WINDOW_CLOSING) { showLine("WINDOW_CLOSING event received."); showLine("Application will exit in 5 seconds"); // Force the updates to appear now. update(this.getGraphics()); // Wait five seconds try { Thread.sleep(5000); } catch (InterruptedException ie) { ; } // Exit now System.exit(0); } } /** The list of lines to display in the window */ protected Vector lines = new Vector(); /** Add a new line to the list of lines, and request redisplay */ protected void showLine(String s) { if (lines.size() == 20) lines.removeElementAt(0); lines.addElement(s); repaint(); } /** This method repaints the text in the window */ public void paintComponent(Graphics g) { for (int i = 0; i < lines.size(); i++) g.drawString((String) lines.elementAt(i), 20, i * 16 + 50); } public boolean isOpaque() { return false; } public static void main(String[] args) { JFrame frame = new JFrame(); frame.addWindowListener(new WindowAdapter() { public void windowClosing(WindowEvent e) { System.exit(0); } }); frame.getContentPane().add(new Main(), BorderLayout.CENTER); // Finally, set the size of the main window, and pop it up. frame.setSize(600, 400); frame.setVisible(true); } }