events.js

用来在地图上做操作GIS,在地图上做标记

/* Copyright (c) 2006-2007 MetaCarta, Inc., published under the BSD license.
 * See http://svn.openlayers.org/trunk/openlayers/release-license.txt 
 * for the full text of the license. */


/**
 * @requires OpenLayers/Util.js
 *
 * Namespace: OpenLayers.Event
 * Utility functions for event handling.
 */
OpenLayers.Event = {

    /** 
     * Property: observers 
     * {Object} A hashtable cache of the event observers. Keyed by
     * element._eventCacheID 
     */
    observers: false,
    
    /** 
     * Constant: KEY_BACKSPACE 
     * {int} 
     */
    KEY_BACKSPACE: 8,

    /** 
     * Constant: KEY_TAB 
     * {int} 
     */
    KEY_TAB: 9,

    /** 
     * Constant: KEY_RETURN 
     * {int} 
     */
    KEY_RETURN: 13,

    /** 
     * Constant: KEY_ESC 
     * {int} 
     */
    KEY_ESC: 27,

    /** 
     * Constant: KEY_LEFT 
     * {int} 
     */
    KEY_LEFT: 37,

    /** 
     * Constant: KEY_UP 
     * {int} 
     */
    KEY_UP: 38,

    /** 
     * Constant: KEY_RIGHT 
     * {int} 
     */
    KEY_RIGHT: 39,

    /** 
     * Constant: KEY_DOWN 
     * {int} 
     */
    KEY_DOWN: 40,

    /** 
     * Constant: KEY_DELETE 
     * {int} 
     */
    KEY_DELETE: 46,


    /**
     * Method: element
     * Cross browser event element detection.
     * 
     * Parameters:
     * event - {Event} 
     * 
     * Returns:
     * {DOMElement} The element that caused the event 
     */
    element: function(event) {
        return event.target || event.srcElement;
    },

    /**
     * Method: isLeftClick
     * Determine whether event was caused by a left click. 
     *
     * Parameters:
     * event - {Event} 
     * 
     * Returns:
     * {Boolean}
     */
    isLeftClick: function(event) {
        return (((event.which) && (event.which == 1)) ||
                ((event.button) && (event.button == 1)));
    },

    /**
     * Method: stop
     * Stops an event from propagating. 
     *
     * Parameters: 
     * event - {Event} 
     * allowDefault - {Boolean} If true, we stop the event chain but 
     *                               still allow the default browser 
     *                               behaviour (text selection, radio-button 
     *                               clicking, etc)
     *                               Default false
     */
    stop: function(event, allowDefault) {
        
        if (!allowDefault) { 
            if (event.preventDefault) {
                event.preventDefault();
            } else {
                event.returnValue = false;
            }
        }
                
        if (event.stopPropagation) {
            event.stopPropagation();
        } else {
            event.cancelBubble = true;
        }
    },

    /** 
     * Method: findElement
     * 
     * Parameters:
     * event - {Event} 
     * tagName - {String} 
     * 
     * Returns:
     * {DOMElement} The first node with the given tagName, starting from the
     * node the event was triggered on and traversing the DOM upwards
     */
    findElement: function(event, tagName) {
        var element = OpenLayers.Event.element(event);
        while (element.parentNode && (!element.tagName ||
              (element.tagName.toUpperCase() != tagName.toUpperCase())))
            element = element.parentNode;
        return element;
    },

    /** 
     * Method: observe
     * 
     * Parameters:
     * elementParam - {DOMElement || String} 
     * name - {String} 
     * observer - {function} 
     * useCapture - {Boolean} 
     */
    observe: function(elementParam, name, observer, useCapture) {
        var element = OpenLayers.Util.getElement(elementParam);
        useCapture = useCapture || false;

        if (name == 'keypress' &&
           (navigator.appVersion.match(/Konqueror|Safari|KHTML/)
           || element.attachEvent)) {
            name = 'keydown';
        }

        //if observers cache has not yet been created, create it
        if (!this.observers) {
            this.observers = {};
        }

        //if not already assigned, make a new unique cache ID
        if (!element._eventCacheID) {
            var idPrefix = "eventCacheID_";
            if (element.id) {
                idPrefix = element.id + "_" + idPrefix;
            }
            element._eventCacheID = OpenLayers.Util.createUniqueID(idPrefix);
        }

        var cacheID = element._eventCacheID;

        //if there is not yet a hash entry for this element, add one
        if (!this.observers[cacheID]) {
            this.observers[cacheID] = [];
        }

        //add a new observer to this element's list
        this.observers[cacheID].push({
            'element': element,
            'name': name,
            'observer': observer,
            'useCapture': useCapture
        });

        //add the actual browser event listener
        if (element.addEventListener) {
            element.addEventListener(name, observer, useCapture);
        } else if (element.attachEvent) {
            element.attachEvent('on' + name, observer);
        }
    },

    /** 
     * Method: stopObservingElement
     * Given the id of an element to stop observing, cycle through the 
     *   element's cached observers, calling stopObserving on each one, 
     *   skipping those entries which can no longer be removed.
     * 
     * parameters:
     * elementParam - {DOMElement || String} 
     */
    stopObservingElement: function(elementParam) {
        var element = OpenLayers.Util.getElement(elementParam);
        var cacheID = element._eventCacheID;

        this._removeElementObservers(OpenLayers.Event.observers[cacheID]);
    },

    /**
     * Method: _removeElementObservers
     *
     * Parameters:
     * elementObservers - {Array(Object)} Array of (element, name, 
     *                                         observer, usecapture) objects, 
     *                                         taken directly from hashtable
     */
    _removeElementObservers: function(elementObservers) {
        if (elementObservers) {
            for(var i = elementObservers.length-1; i >= 0; i--) {
                var entry = elementObservers[i];
                var args = new Array(entry.element,
                                     entry.name,
                                     entry.observer,
                                     entry.useCapture);
                var removed = OpenLayers.Event.stopObserving.apply(this, args);
            }
        }
    },

    /**
     * Method: stopObserving
     * 
     * Parameters:
     * elementParam - {DOMElement || String} 
     * name - {String} 
     * observer - {function} 
     * useCapture - {Boolean} 
     *  
     * Returns:
     * {Boolean} Whether or not the event observer was removed
     */
    stopObserving: function(elementParam, name, observer, useCapture) {
        useCapture = useCapture || false;
    
        var element = OpenLayers.Util.getElement(elementParam);
        var cacheID = element._eventCacheID;

        if (name == 'keypress') {
            if ( navigator.appVersion.match(/Konqueror|Safari|KHTML/) || 
                 element.detachEvent) {
              name = 'keydown';
            }
        }

        // find element's entry in this.observers cache and remove it
        var foundEntry = false;
        var elementObservers = OpenLayers.Event.observers[cacheID];
        if (elementObservers) {
    
            // find the specific event type in the element's list
            var i=0;
            while(!foundEntry && i < elementObservers.length) {
                var cacheEntry = elementObservers[i];
    
                if ((cacheEntry.name == name) &&
                    (cacheEntry.observer == observer) &&
                    (cacheEntry.useCapture == useCapture)) {
    
                    elementObservers.splice(i, 1);
                    if (elementObservers.length == 0) {
                        delete OpenLayers.Event.observers[cacheID];
                    }
                    foundEntry = true;
                    break; 
                }
                i++;           
            }
        }
    
        //actually remove the event listener from browser
        if (element.removeEventListener) {
            element.removeEventListener(name, observer, useCapture);
        } else if (element && element.detachEvent) {
            element.detachEvent('on' + name, observer);
        }
        return foundEntry;
    },
    
    /** 
     * Method: unloadCache
     * Cycle through all the element entries in the events cache and call
     *   stopObservingElement on each. 
     */
    unloadCache: function() {
        if (OpenLayers.Event.observers) {
            for (var cacheID in OpenLayers.Event.observers) {
                var elementObservers = OpenLayers.Event.observers[cacheID];
                OpenLayers.Event._removeElementObservers.apply(this, 
                                                           [elementObservers]);
            }
            OpenLayers.Event.observers = false;
        }
    },

    CLASS_NAME: "OpenLayers.Event"
};

/* prevent memory leaks in IE */
OpenLayers.Event.observe(window, 'unload', OpenLayers.Event.unloadCache, false);

// FIXME: Remove this in 3.0. In 3.0, Event.stop will no longer be provided
// by OpenLayers.
if (window.Event) {
    OpenLayers.Util.applyDefaults(window.Event, OpenLayers.Event);
} else {
    var Event = OpenLayers.Event;
}

/**
 * Class: OpenLayers.Events
 */