alerttype.java

有关j2me的很好的例子可以研究一下

/*
 * @(#)AlertType.java	1.9 01/07/10
 * Copyright (c) 1999-2001 Sun Microsystems, Inc. All Rights Reserved.
 *
 * This software is the confidential and proprietary information of Sun
 * Microsystems, Inc. ("Confidential Information").  You shall not
 * disclose such Confidential Information and shall use it only in
 * accordance with the terms of the license agreement you entered into
 * with Sun.
 *
 * SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF THE
 * SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
 * PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR ANY DAMAGES
 * SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR DISTRIBUTING
 * THIS SOFTWARE OR ITS DERIVATIVES.
 */
package javax.microedition.lcdui;

/**
 * The AlertType provides an indication of the nature of alerts.
 * Alerts are used by an application to present various kinds of
 * information to the user. 
 * An AlertType may be used to directly signal the user without changing
 * the current Displayable.
 * The <code>playSound</code> method can be used to spontaneously
 * generate a sound to alert the user.  For example, a game using a 
 * Canvas can use <code>playSound</code> to indicate success or progress.
 *
 * The predefined types are <CODE>INFO</CODE>, <CODE>WARNING</CODE>,
 * <CODE>ERROR</CODE>, <CODE>ALARM</CODE>, and <CODE>CONFIRMATION</CODE>.
 * <p>
 * 
 * @see Alert
 */
public class AlertType {
    /**
     * Information Alert identifier
     */
    static final int ALERT_INFO = 1;
    /**
     * Warning Alert identifier
     */
    static final int ALERT_WARN = 2;
    /**
     * Error Alert identifier
     */
    static final int ALERT_ERR  = 3;
    /**
     * Alarm Alert identifier
     */
    static final int ALERT_ALRM = 4;
    /**
     * Confirmation Alert identifier
     */
    static final int ALERT_CFM  = 5;
  
    /**
     * An INFO AlertType typically provides non-threatening information to the
     * user. For example, a simple splash screen might be an INFO AlertType.
     */
    public static final AlertType INFO = new AlertType(ALERT_INFO);

    /**
     * A WARNING AlertType is a hint to warn the user of a potentially
     * dangerous operation.
     * For example, the warning message may contain the message, "Warning:
     * this operation will erase your data."
     */
    public static final AlertType WARNING = new AlertType(ALERT_WARN);

    /**
     * An ERROR AlertType is a hint to alert the user to an erroneous operation.
     * For example, an error alert might show the message,
     * "There is not enough room to install the application."
     */
    public static final AlertType ERROR = new AlertType(ALERT_ERR);
    
    /**
     * An ALARM AlertType is a hint to alert the user to an event for which
     * the user has previously requested to be notified.
     * For example, the message might say, "Staff meeting in five minutes."
     */
    public static final AlertType ALARM = new AlertType(ALERT_ALRM);
    
    /**
     * A CONFIRMATION AlertType is a hint to confirm user actions.
     * For example, "Saved!" might be shown to indicate that a Save 
     * operation has completed.
     */
    public static final AlertType CONFIRMATION = new AlertType(ALERT_CFM);

    /**
     * Protected constructor for subclasses.
     */
    protected AlertType() {
    }


    /**
     * Alert the user by playing the sound for this AlertType.
     * The AlertType instance is used as a hint by the device
     * to generate an appropriate sound.  Instances other than
     * those predefined above may be ignored.
     * The actual sound made by the device,
     * if any, is determined by the device. The device may
     * ignore the request, use the same sound for
     * several AlertTypes or use any other means suitable to alert 
     * the user.
     *
     * @param display to which the AlertType's sound should be played.
     * @return <code>true</code> if the user was alerted,
     *		<code>false</code> otherwise.
     * @throws NullPointerException if <code>display</code> is <code>null</code>
     */
    public boolean playSound(Display display) {
        synchronized (Display.LCDUILock) {
            return display.playAlertSound(this);
        }
    }

    /* we don't need a subclass...this private implementation will do. */

    /**
     * The type of this AlertType
     */
    private int type;

    /**
     * Create a new AlertType given the type identifier
     *
     * @param type  The type of the new AlertType
     */
    AlertType(int type) {
        this.type = type;
    }

    /**
     * Get the type of this AlertType
     *
     * @return int  The typer identifer of this AlertType, one of:
     *              ALERT_INFO, ALERT_WARN, ALERT_ERR, ALERT_ALRM, ALERT_CFM
     */
    int getType() {
        return this.type;
    }

}