OLZ Vz.1.1 到 Vz.8.2 打破了 Pouchdb 的 w=10=sh

Question

我最近将我的 Cordova 移动地图应用程序从 OL3 V3.1.1 更新到 V3.7.0 再到 V3.8.2。

我正在使用 PouchDB 存储离线图块，并且在 V3.1.1 中图块是可见的。这是代码片段：

    OSM_bc_offline_pouchdb = new ol.layer.Tile({
        //maxResolution: 5000,
        //extent: BC,
        //projection: spherical_mercator,
        //crossOrigin: 'anonymous',
        source: new ol.source.XYZ({
            //adapted from: http://jsfiddle.net/gussy/LCNWC/
            tileLoadFunction: function (imageTile, src) {
                pouchTilesDB_osm_bc_baselayer.getAttachment(src, 'tile', function (err, res) {
                    if (err && err.error == 'not_found')
                        return;
                    //if(!res) return;  // ?issue -> causes map refresh on movement to stop 
                    imageTile.getImage().src = window.URL.createObjectURL(res);
                });
            },
            tileUrlFunction: function (coordinate, projection) {
                if (coordinate == null)
                    return undefined;
                // OSM NW origin style URL
                var z = coordinate[0];
                var x = coordinate[1];
                var y = coordinate[2];
                var imgURL = ["tile", z, x, y].join('_');
                return imgURL;
            }
        })
    });
    trails_mobileMap.addLayer(OSM_bc_offline_pouchdb);
    OSM_bc_offline_pouchdb.setVisible(true);

移动到 V3.7.0 和 V3.8.2 会导致磁贴不显示。阅读 API，我不知道为什么会发生这种情况。

我的代码中的哪些内容需要更新才能与 OL-V3.8.2 一起使用？

谢谢，彼得

Answer 1

您的问题可能与 OpenLayers 3.7.0 中 ol.TileCoord 的更改有关。来自发行说明：

Until now, the API exposed two different types of ol.TileCoord tile coordinates: internal ones that increase left to right and upward, and transformed ones that may increase downward, as defined by a transform function on the tile grid. With this change, the API now only exposes tile coordinates that increase left to right and upward.

Previously, tile grids created by OpenLayers either had their origin at the top-left or at the bottom-left corner of the extent. To make it easier for application developers to transform tile coordinates to the common XYZ tiling scheme, all tile grids that OpenLayers creates internally have their origin now at the top-left corner of the extent.

This change affects applications that configure a custom tileUrlFunction for an ol.source.Tile. Previously, the tileUrlFunction was called with rather unpredictable tile coordinates, depending on whether a tile coordinate transform took place before calling the tileUrlFunction. Now it is always called with OpenLayers tile coordinates. To transform these into the common XYZ tiling scheme, a custom tileUrlFunction has to change the y value (tile row) of the ol.TileCoord:

function tileUrlFunction = function(tileCoord, pixelRatio, projection){
  var urlTemplate = '{z}/{x}/{y}';
  return urlTemplate
      .replace('{z}', tileCoord[0].toString())
      .replace('{x}', tileCoord[1].toString())
      .replace('{y}', (-tileCoord[2] - 1).toString());
}

如果这是您的问题，请尝试将您的 tileUrlFunction 更改为

function (coordinate, projection) {
    if (coordinate == null)
        return undefined;
    // OSM NW origin style URL
    var z = coordinate[0];
    var x = coordinate[1];
    var y = (-coordinate[2] - 1);
    var imgURL = ["tile", z, x, y].join('_');
    return imgURL;
}

OLZ Vz.1.1 到 Vz.8.2 打破了 Pouchdb 的 w=10=sh

OL3 V3.1.1 to V3.8.2 broke ol.source.xyz from PouchDB

openlayers-3

pouchdb