grid.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/Layer/HTTPRequest.js
 * 
 * Class: OpenLayers.Layer.Grid
 * Base class for layers that use a lattice of tiles.  Create a new grid
 * layer with the <OpenLayers.Layer.Grid> constructor.
 *
 * Inherits from:
 *  - <OpenLayers.Layer.HTTPRequest>
 */
OpenLayers.Layer.Grid = OpenLayers.Class(OpenLayers.Layer.HTTPRequest, {
    
    /**
     * APIProperty: tileSize
     * {<OpenLayers.Size>}
     */
    tileSize: null,
    
    /**
     * Property: grid
     * {Array(Array(<OpenLayers.Tile>))} This is an array of rows, each row is 
     *     an array of tiles.
     */
    grid: null,

    /**
     * APIProperty: singleTile
     * {Boolean} Moves the layer into single-tile mode, meaning that one tile 
     *     will be loaded. The tile's size will be determined by the 'ratio'
     *     property. When the tile is dragged such that it does not cover the 
     *     entire viewport, it is reloaded.
     */
    singleTile: false,

    /** APIProperty: ratio
     *  {Float} Used only when in single-tile mode, this specifies the 
     *          ratio of the size of the single tile to the size of the map.
     */
    ratio: 1.5,

    /**
     * APIProperty: buffer
     * {Integer} Used only when in gridded mode, this specifies the number of 
     *           extra rows and colums of tiles on each side which will
     *           surround the minimum grid tiles to cover the map.
     */
    buffer: 2,

    /**
     * APIProperty: numLoadingTiles
     * {Integer} How many tiles are still loading?
     */
    numLoadingTiles: 0,

    /**
     * Constructor: OpenLayers.Layer.Grid
     * Create a new grid layer
     *
     * Parameters:
     * name - {String}
     * url - {String}
     * params - {Object}
     * options - {Object} Hashtable of extra options to tag onto the layer
     */
    initialize: function(name, url, params, options) {
        OpenLayers.Layer.HTTPRequest.prototype.initialize.apply(this, 
                                                                arguments);
        
        //grid layers will trigger 'tileloaded' when each new tile is 
        // loaded, as a means of progress update to listeners.
        // listeners can access 'numLoadingTiles' if they wish to keep track
        // of the loading progress
        //
        this.events.addEventType("tileloaded");

        this.grid = [];
    },

    /**
     * APIMethod: destroy
     * Deconstruct the layer and clear the grid.
     */
    destroy: function() {
        this.clearGrid();
        this.grid = null;
        this.tileSize = null;
        OpenLayers.Layer.HTTPRequest.prototype.destroy.apply(this, arguments); 
    },

    /**
     * Method: clearGrid
     * Go through and remove all tiles from the grid, calling
     *    destroy() on each of them to kill circular references
     */
    clearGrid:function() {
        if (this.grid) {
            for(var iRow=0; iRow < this.grid.length; iRow++) {
                var row = this.grid[iRow];
                for(var iCol=0; iCol < row.length; iCol++) {
                    var tile = row[iCol];
                    this.removeTileMonitoringHooks(tile);
                    tile.destroy();
                }
            }
            this.grid = [];
        }
    },

    /**
     * APIMethod: clone
     * Create a clone of this layer
     *
     * Parameters:
     * obj - {Object} Is this ever used?
     * 
     * Returns:
     * {<OpenLayers.Layer.Grid>} An exact clone of this OpenLayers.Layer.Grid
     */
    clone: function (obj) {
        
        if (obj == null) {
            obj = new OpenLayers.Layer.Grid(this.name,
                                            this.url,
                                            this.params,
                                            this.options);
        }

        //get all additions from superclasses
        obj = OpenLayers.Layer.HTTPRequest.prototype.clone.apply(this, [obj]);

        // copy/set any non-init, non-simple values here
        if (this.tileSize != null) {
            obj.tileSize = this.tileSize.clone();
        }
        
        // we do not want to copy reference to grid, so we make a new array
        obj.grid = [];

        return obj;
    },    

    /**
     * Method: moveTo
     * This function is called whenever the map is moved. All the moving
     * of actual 'tiles' is done by the map, but moveTo's role is to accept
     * a bounds and make sure the data that that bounds requires is pre-loaded.
     *
     * Parameters:
     * bounds - {<OpenLayers.Bounds>}
     * zoomChanged - {Boolean}
     * dragging - {Boolean}
     */
    moveTo:function(bounds, zoomChanged, dragging) {
        OpenLayers.Layer.HTTPRequest.prototype.moveTo.apply(this, arguments);
        
        bounds = bounds || this.map.getExtent();

        if (bounds != null) {
             
            // if grid is empty or zoom has changed, we *must* re-tile
            var forceReTile = !this.grid.length || zoomChanged;

            // total bounds of the tiles
            var tilesBounds = this.getTilesBounds();            
      
            if (this.singleTile) {
                
                // We want to redraw whenever even the slightest part of the 
                //  current bounds is not contained by our tile.
                //  (thus, we do not specify partial -- its default is false)
                if ( forceReTile || 
                     (!dragging && !tilesBounds.containsBounds(bounds))) {
                    this.initSingleTile(bounds);
                }
            } else {
             
                // if the bounds have changed such that they are not even 
                //  *partially* contained by our tiles (IE user has 
                //  programmatically panned to the other side of the earth) 
                //  then we want to reTile (thus, partial true).  
                //
                if (forceReTile || !tilesBounds.containsBounds(bounds, true)) {
                    this.initGriddedTiles(bounds);
                } else {
                    //we might have to shift our buffer tiles
                    this.moveGriddedTiles(bounds);
                }
            }
        }
    },
    
    /**
     * APIMethod: setTileSize
     * Check if we are in singleTile mode and if so, set the size as a ratio
     *     of the map size (as specified by the layer's 'ratio' property).
     * 
     * Parameters:
     * size - {<OpenLayers.Size>}
     */
    setTileSize: function(size) { 
        if (this.singleTile) {
            var size = this.map.getSize().clone();
            size.h = parseInt(size.h * this.ratio);
            size.w = parseInt(size.w * this.ratio);
        } 
        OpenLayers.Layer.HTTPRequest.prototype.setTileSize.apply(this, [size]);
    },
        
    /**
     * Method: getGridBounds
     * Deprecated. This function will be removed in 3.0. Please use 
     *     getTilesBounds() instead.
     * 
     * Returns:
     * {<OpenLayers.Bounds>} A Bounds object representing the bounds of all the
     * currently loaded tiles (including those partially or not at all seen 
     * onscreen)
     */
    getGridBounds: function() {
        var msg = "The getGridBounds() function is deprecated. It will be " +
                  "removed in 3.0. Please use getTilesBounds() instead.";
        OpenLayers.Console.warn(msg);
        return this.getTilesBounds();
    },

    /**
     * APIMethod: getTilesBounds
     * Return the bounds of the tile grid.
     *
     * Returns:
     * {<OpenLayers.Bounds>} A Bounds object representing the bounds of all the
     *     currently loaded tiles (including those partially or not at all seen 
     *     onscreen).
     */
    getTilesBounds: function() {    
        var bounds = null; 
        
        if (this.grid.length) {
            var bottom = this.grid.length - 1;
            var bottomLeftTile = this.grid[bottom][0];
    
            var right = this.grid[0].length - 1; 
            var topRightTile = this.grid[0][right];
    
            bounds = new OpenLayers.Bounds(bottomLeftTile.bounds.left, 
                                           bottomLeftTile.bounds.bottom,
                                           topRightTile.bounds.right, 
                                           topRightTile.bounds.top);
            
        }   
        return bounds;
    },

    /**
     * Method: initSingleTile
     * 
     * Parameters: 
     * bounds - {<OpenLayers.Bounds>}
     */
    initSingleTile: function(bounds) {

        //determine new tile bounds
        var center = bounds.getCenterLonLat();
        var tileWidth = bounds.getWidth() * this.ratio;
        var tileHeight = bounds.getHeight() * this.ratio;
                                       
        var tileBounds = 
            new OpenLayers.Bounds(center.lon - (tileWidth/2),
                                  center.lat - (tileHeight/2),
                                  center.lon + (tileWidth/2),
                                  center.lat + (tileHeight/2));
  
        var ul = new OpenLayers.LonLat(tileBounds.left, tileBounds.top);
        var px = this.map.getLayerPxFromLonLat(ul);

        if (!this.grid.length) {
            this.grid[0] = [];
        }

        var tile = this.grid[0][0];
        if (!tile) {
            tile = this.addTile(tileBounds, px);
            
            this.addTileMonitoringHooks(tile);
            tile.draw();
            this.grid[0][0] = tile;
        } else {
            tile.moveTo(tileBounds, px);
        }           
        
        //remove all but our single tile
        this.removeExcessTiles(1,1);
    },

    /**
     * Method: initGriddedTiles
     * 
     * Parameters:
     * bounds - {<OpenLayers.Bounds>}
     */
    initGriddedTiles:function(bounds) {
        
        // work out mininum number of rows and columns; this is the number of
        // tiles required to cover the viewport plus at least one for panning

        var viewSize = this.map.getSize();
        var minRows = Math.ceil(viewSize.h/this.tileSize.h) + 
                      Math.max(1, 2 * this.buffer);
        var minCols = Math.ceil(viewSize.w/this.tileSize.w) +
                      Math.max(1, 2 * this.buffer);
        
        var extent = this.map.getMaxExtent();
        var resolution = this.map.getResolution();
        var tilelon = resolution * this.tileSize.w;
        var tilelat = resolution * this.tileSize.h;
        
        var offsetlon = bounds.left - extent.left;
        var tilecol = Math.floor(offsetlon/tilelon) - this.buffer;
        var tilecolremain = offsetlon/tilelon - tilecol;
        var tileoffsetx = -tilecolremain * this.tileSize.w;
        var tileoffsetlon = extent.left + tilecol * tilelon;
        
        var offsetlat = bounds.top - (extent.bottom + tilelat);  
        var tilerow = Math.ceil(offsetlat/tilelat) + this.buffer;
        var tilerowremain = tilerow - offsetlat/tilelat;
        var tileoffsety = -tilerowremain * this.tileSize.h;
        var tileoffsetlat = extent.bottom + tilerow * tilelat;
        
        tileoffsetx = Math.round(tileoffsetx); // heaven help us
        tileoffsety = Math.round(tileoffsety);

        this.origin = new OpenLayers.Pixel(tileoffsetx, tileoffsety);

        var startX = tileoffsetx; 
        var startLon = tileoffsetlon;

        var rowidx = 0;
    
        do {
            var row = this.grid[rowidx++];
            if (!row) {
                row = [];
                this.grid.push(row);
            }

            tileoffsetlon = startLon;
            tileoffsetx = startX;
            var colidx = 0;
 
            do {