displayaccess.java

有关j2me的很好的例子可以研究一下

/*
 * @(#)DisplayAccess.java	1.12 01/08/12
 *
 * Copyright (c) 2000-2001 Sun Microsystems, Inc., 901 San Antonio Road,
 * Palo Alto, CA 94303, U.S.A.  All Rights Reserved.
 * 
 * Sun Microsystems, Inc. has intellectual property rights relating
 * to the technology embodied in this software.  In particular, and
 * without limitation, these intellectual property rights may include
 * one or more U.S. patents, foreign patents, or pending
 * applications.  Sun, Sun Microsystems, the Sun logo, Java, KJava,
 * and all Sun-based and Java-based marks are trademarks or
 * registered trademarks of Sun Microsystems, Inc.  in the United
 * States and other countries.
 *
 * This software is distributed under licenses restricting its use,
 * copying, distribution, and decompilation.  No part of this
 * software may be reproduced in any form by any means without prior
 * written authorization of Sun and its licensors, if any.
 *
 * FEDERAL ACQUISITIONS:  Commercial Software -- Government Users
 * Subject to Standard License Terms and Conditions
 */
package com.sun.midp.lcdui;

import javax.microedition.lcdui.Display;

/**
 * Public interface for an object that is used to provide internal access
 * to a Display object, across package boundaries.  The object implements
 * this interface, and is created inside the same package as Display,  so
 * that it has access to private instance data of Display as necessary.
 */
public interface DisplayAccess {
    /**
     * Get the Display object that is associated with this DisplayAccess.
     * @return Display The Display object.
     */
    Display getDisplay();

    /**
     * Called by event delivery when an abstract Command is fired.
     * The parameter is an index into the list of Commands that are
     * current, i.e. those associated with the visible Screen.
     * @param id The integer id of the Command that fired (as returned
     *           by Command.getID())
     */
    void commandAction(int id);

    /**
     * Called by event delivery when a pen event is processed.
     * The type is one of EventHandler.PRESSED, EventHandler.RELEASED,
     * or EventHandler.DRAGGED.
     * @param type The type of event (press, release or drag)
     * @param x The x coordinate of the location of the pen     
     * @param y The y coordinate of the location of the pen     
     */
    void pointerEvent(int type, int x, int y);

    /**
     * Called by event delivery when a key event is processed.
     * The type is one of EventHandler.PRESSED, EventHandler.RELEASED,
     * or EventHandler.REPEATED.
     * @param type The type of event (press, release or repeat)
     * @param keyCode The key code for the key that registered the event
     */
    void keyEvent(int type, int keyCode);

    /**
     * Called by event delivery when an internal timer is processed.
     * (This is not the same as the Timer events provided in java.util.Timer).
     * The type is one of EventHandler.REPAINT or EventHandler.SCREEN.
     * @param type The type of event (repaint or screen change).
     */
    void timerEvent(int type);

    /* suspend and resume repaint processing */
    /* this helps prevent animation from clobbering the display */
    /* while native processing (e.g. a menu) is in charge */

    /**
     * Called when the system needs to temporarily prevent the application
     * from painting the screen.  The primary use of this method is to allow
     * a system service to temporarily utilize the screen, e.g. to provide
     * input method or abstract command processing.
     *
     * This method should prevent application-based paints (i.e. those
     * generated by Canvas.repaint(), Canvas.serviceRepaints() or some
     * internal paint method on another kind of Displayable) from changing
     * the contents of the screen in any way.
     */
    void suspendPainting();

    /**
     * Called when the system is ready to give up its control over the
     * screen.  The application should receive a request for a full
     * repaint when this is called, and is subsequently free to process
     * paint events from Canvas.repaint(), Canvas.serviceRepaints() or
     * internal paint methods on Displayable.
     */
    void resumePainting();

    /**
     * This is for the benefit of the MIDLet manager; it is called to tell
     * the Display that its MIDLet has become the "foreground midlet" and
     * is therefore allowed to receive events and to paint, or has lost 
     * the foreground and should relinquish those privileges.
     *
     * @param hasForeground A flag indicating the foreground status.
     */
    void setForeground(boolean hasForeground);

    /**
     * Called by event delivery when an input method event is processed.
     * @param str The string from the input method.
     */
    void inputMethodEvent(String str);

    /**
     * Get the flag indicating that the most recent call to setCurrent
     * was for a non-null Displayable.
     * This allows the implementation of the hint provided
     * to the MIDlet schedule to determine which MIDlet to make foreground.
     *
     * @return <code>true</code> if the MIDlet has a screen to display;
     * otherwise <code>false</code> if MIDlet has indicated that it
     * does not need the display.
     */
    boolean hasCurrent();
}