grid.js

来自「用来在地图上做操作GIS,在地图上做标记」· JavaScript 代码 · 共 710 行 · 第 1/2 页

                var tileBounds = 
                    new OpenLayers.Bounds(tileoffsetlon, 
                                          tileoffsetlat, 
                                          tileoffsetlon + tilelon,
                                          tileoffsetlat + tilelat);

                var x = tileoffsetx;
                x -= parseInt(this.map.layerContainerDiv.style.left);

                var y = tileoffsety;
                y -= parseInt(this.map.layerContainerDiv.style.top);

                var px = new OpenLayers.Pixel(x, y);
                var tile = row[colidx++];
                if (!tile) {
                    tile = this.addTile(tileBounds, px);
                    this.addTileMonitoringHooks(tile);
                    row.push(tile);
                } else {
                    tile.moveTo(tileBounds, px, false);
                }
     
                tileoffsetlon += tilelon;       
                tileoffsetx += this.tileSize.w;
            } while ((tileoffsetlon <= bounds.right + tilelon * this.buffer)
                     || colidx < minCols)  
             
            tileoffsetlat -= tilelat;
            tileoffsety += this.tileSize.h;
        } while((tileoffsetlat >= bounds.bottom - tilelat * this.buffer)
                || rowidx < minRows)
        
        //shave off exceess rows and colums
        this.removeExcessTiles(rowidx, colidx);

        //now actually draw the tiles
        this.spiralTileLoad();
    },
    
    /**
     * Method: spiralTileLoad
     *   Starts at the top right corner of the grid and proceeds in a spiral 
     *    towards the center, adding tiles one at a time to the beginning of a 
     *    queue. 
     * 
     *   Once all the grid's tiles have been added to the queue, we go back 
     *    and iterate through the queue (thus reversing the spiral order from 
     *    outside-in to inside-out), calling draw() on each tile. 
     */
    spiralTileLoad: function() {
        var tileQueue = [];
 
        var directions = ["right", "down", "left", "up"];

        var iRow = 0;
        var iCell = -1;
        var direction = OpenLayers.Util.indexOf(directions, "right");
        var directionsTried = 0;
        
        while( directionsTried < directions.length) {

            var testRow = iRow;
            var testCell = iCell;

            switch (directions[direction]) {
                case "right":
                    testCell++;
                    break;
                case "down":
                    testRow++;
                    break;
                case "left":
                    testCell--;
                    break;
                case "up":
                    testRow--;
                    break;
            } 
    
            // if the test grid coordinates are within the bounds of the 
            //  grid, get a reference to the tile.
            var tile = null;
            if ((testRow < this.grid.length) && (testRow >= 0) &&
                (testCell < this.grid[0].length) && (testCell >= 0)) {
                tile = this.grid[testRow][testCell];
            }
            
            if ((tile != null) && (!tile.queued)) {
                //add tile to beginning of queue, mark it as queued.
                tileQueue.unshift(tile);
                tile.queued = true;
                
                //restart the directions counter and take on the new coords
                directionsTried = 0;
                iRow = testRow;
                iCell = testCell;
            } else {
                //need to try to load a tile in a different direction
                direction = (direction + 1) % 4;
                directionsTried++;
            }
        } 
        
        // now we go through and draw the tiles in forward order
        for(var i=0; i < tileQueue.length; i++) {
            var tile = tileQueue[i]
            tile.draw();
            //mark tile as unqueued for the next time (since tiles are reused)
            tile.queued = false;       
        }
    },

    /**
     * APIMethod: addTile
     * Gives subclasses of Grid the opportunity to create an 
     * OpenLayer.Tile of their choosing. The implementer should initialize 
     * the new tile and take whatever steps necessary to display it.
     *
     * Parameters
     * bounds - {<OpenLayers.Bounds>}
     *
     * Returns:
     * {<OpenLayers.Tile>} The added OpenLayers.Tile
     */
    addTile:function(bounds, position) {
        // Should be implemented by subclasses
    },
    
    /** 
     * Method: addTileMonitoringHooks
     * This function takes a tile as input and adds the appropriate hooks to 
     *     the tile so that the layer can keep track of the loading tiles.
     * 
     * Parameters: 
     * tile - {<OpenLayers.Tile>}
     */
    addTileMonitoringHooks: function(tile) {
        
        tile.onLoadStart = function() {
            //if that was first tile then trigger a 'loadstart' on the layer
            if (this.numLoadingTiles == 0) {
                this.events.triggerEvent("loadstart");
            }
            this.numLoadingTiles++;
        };
        tile.events.register("loadstart", this, tile.onLoadStart);
      
        tile.onLoadEnd = function() {
            this.numLoadingTiles--;
            this.events.triggerEvent("tileloaded");
            //if that was the last tile, then trigger a 'loadend' on the layer
            if (this.numLoadingTiles == 0) {
                this.events.triggerEvent("loadend");
            }
        };
        tile.events.register("loadend", this, tile.onLoadEnd);
    },

    /** 
     * Method: removeTileMonitoringHooks
     * This function takes a tile as input and removes the tile hooks 
     *     that were added in addTileMonitoringHooks()
     * 
     * Parameters: 
     * tile - {<OpenLayers.Tile>}
     */
    removeTileMonitoringHooks: function(tile) {
        tile.events.unregister("loadstart", this, tile.onLoadStart);
        tile.events.unregister("loadend", this, tile.onLoadEnd);
    },
    
    /**
     * Method: moveGriddedTiles
     * 
     * Parameters:
     * bounds - {<OpenLayers.Bounds>}
     */
    moveGriddedTiles: function(bounds) {
        var buffer = this.buffer || 1;
        while (true) {
            var tlLayer = this.grid[0][0].position;
            var tlViewPort = 
                this.map.getViewPortPxFromLayerPx(tlLayer);
            if (tlViewPort.x > -this.tileSize.w * (buffer - 1)) {
                this.shiftColumn(true);
            } else if (tlViewPort.x < -this.tileSize.w * buffer) {
                this.shiftColumn(false);
            } else if (tlViewPort.y > -this.tileSize.h * (buffer - 1)) {
                this.shiftRow(true);
            } else if (tlViewPort.y < -this.tileSize.h * buffer) {
                this.shiftRow(false);
            } else {
                break;
            }
        };
        if (this.buffer == 0) {
            for (var r=0, rl=this.grid.length; r<rl; r++) {
                var row = this.grid[r];
                for (var c=0, cl=row.length; c<cl; c++) {
                    var tile = row[c];
                    if (!tile.drawn && 
                         tile.bounds.intersectsBounds(bounds, false)) {
                        tile.draw();
                    }
                }
            }
        }
    },

    /**
     * Method: shiftRow
     * Shifty grid work
     *
     * Parameters:
     * prepend - {Boolean} if true, prepend to beginning.
     *                          if false, then append to end
     */
    shiftRow:function(prepend) {
        var modelRowIndex = (prepend) ? 0 : (this.grid.length - 1);
        var modelRow = this.grid[modelRowIndex];

        var resolution = this.map.getResolution();
        var deltaY = (prepend) ? -this.tileSize.h : this.tileSize.h;
        var deltaLat = resolution * -deltaY;

        var row = (prepend) ? this.grid.pop() : this.grid.shift();

        for (var i=0; i < modelRow.length; i++) {
            var modelTile = modelRow[i];
            var bounds = modelTile.bounds.clone();
            var position = modelTile.position.clone();
            bounds.bottom = bounds.bottom + deltaLat;
            bounds.top = bounds.top + deltaLat;
            position.y = position.y + deltaY;
            row[i].moveTo(bounds, position);
        }

        if (prepend) {
            this.grid.unshift(row);
        } else {
            this.grid.push(row);
        }
    },

    /**
     * Method: shiftColumn
     * Shift grid work in the other dimension
     *
     * Parameters:
     * prepend - {Boolean} if true, prepend to beginning.
     *                          if false, then append to end
     */
    shiftColumn: function(prepend) {
        var deltaX = (prepend) ? -this.tileSize.w : this.tileSize.w;
        var resolution = this.map.getResolution();
        var deltaLon = resolution * deltaX;

        for (var i=0; i<this.grid.length; i++) {
            var row = this.grid[i];
            var modelTileIndex = (prepend) ? 0 : (row.length - 1);
            var modelTile = row[modelTileIndex];
            
            var bounds = modelTile.bounds.clone();
            var position = modelTile.position.clone();
            bounds.left = bounds.left + deltaLon;
            bounds.right = bounds.right + deltaLon;
            position.x = position.x + deltaX;

            var tile = prepend ? this.grid[i].pop() : this.grid[i].shift()
            tile.moveTo(bounds, position);
            if (prepend) {
                this.grid[i].unshift(tile);
            } else {
                this.grid[i].push(tile);
            }
        }
    },
    
    /**
     * Method: removeExcessTiles
     * When the size of the map or the buffer changes, we may need to
     *     remove some excess rows and columns.
     * 
     * Parameters:
     * rows - {Integer} Maximum number of rows we want our grid to have.
     * colums - {Integer} Maximum number of columns we want our grid to have.
     */
    removeExcessTiles: function(rows, columns) {
        
        // remove extra rows
        while (this.grid.length > rows) {
            var row = this.grid.pop();
            for (var i=0, l=row.length; i<l; i++) {
                var tile = row[i];
                this.removeTileMonitoringHooks(tile)
                tile.destroy();
            }
        }
        
        // remove extra columns
        while (this.grid[0].length > columns) {
            for (var i=0, l=this.grid.length; i<l; i++) {
                var row = this.grid[i];
                var tile = row.pop();
                this.removeTileMonitoringHooks(tile);
                tile.destroy();
            }
        }
    },

    /**
     * Method: onMapResize
     * For singleTile layers, this will replace the tile with the
     * a new one with updated tileSize and extent.
     */
    onMapResize: function() {
      if (this.singleTile) {
        this.clearGrid();
        this.setTileSize();
        this.initSingleTile(this.map.getExtent());
      }
    },
    
    /**
     * APIMethod: getTileBounds
     * Returns The tile bounds for a layer given a pixel location.
     *
     * Parameters:
     * viewPortPx - {<OpenLayers.Pixel>} The location in the viewport.
     *
     * Returns:
     * {<OpenLayers.Bounds>} Bounds of the tile at the given pixel location.
     */
    getTileBounds: function(viewPortPx) {
        var maxExtent = this.map.getMaxExtent();
        var resolution = this.getResolution();
        var tileMapWidth = resolution * this.tileSize.w;
        var tileMapHeight = resolution * this.tileSize.h;
        var mapPoint = this.getLonLatFromViewPortPx(viewPortPx);
        var tileLeft = maxExtent.left + (tileMapWidth *
                                         Math.floor((mapPoint.lon -
                                                     maxExtent.left) /
                                                    tileMapWidth));
        var tileBottom = maxExtent.bottom + (tileMapHeight *
                                             Math.floor((mapPoint.lat -
                                                         maxExtent.bottom) /
                                                        tileMapHeight));
        return new OpenLayers.Bounds(tileLeft, tileBottom,
                                     tileLeft + tileMapWidth,
                                     tileBottom + tileMapHeight);
    },
    
    CLASS_NAME: "OpenLayers.Layer.Grid"
});