Adding CacheRead and CacheWrite controls.
These controls read from and write to the browser's offline storage. Example with a seeding tool included.
This commit is contained in:
ahocevar
@@ -0,0 +1,43 @@
|
||||
<!DOCTYPE html>
|
||||
<html>
|
||||
<head>
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
|
||||
<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0">
|
||||
<meta name="apple-mobile-web-app-capable" content="yes">
|
||||
<title>OpenLayers Offline Storage Example</title>
|
||||
<link rel="stylesheet" href="../theme/default/style.css" type="text/css">
|
||||
<link rel="stylesheet" href="style.css" type="text/css">
|
||||
<style type="text/css">
|
||||
.olControlAttribution {
|
||||
bottom: 0;
|
||||
}
|
||||
</style>
|
||||
<script src="../lib/OpenLayers.js"></script>
|
||||
<script src="offline-storage.js"></script>
|
||||
</head>
|
||||
<body onload="init()">
|
||||
<h1 id="title">Offline Storage Example</h1>
|
||||
|
||||
<div id="tags">
|
||||
local storage, persistence, cache, html5
|
||||
</div>
|
||||
|
||||
<div id="shortdesc">Caching viewed tiles</div>
|
||||
|
||||
<div id="map" class="smallmap"></div>
|
||||
<div>Cache status: <span id="hits"></span> <span id="status"></span></div>
|
||||
<div><input id="read" type="checkbox">Read from cache [<input id="tileloadstart" name="type" type="radio">try cache first] [<input id="tileerror" name="type" type="radio">try online first<sup>1</sup>]</div>
|
||||
<div><input id="write" type="checkbox">Write to cache</div>
|
||||
<div><button id="clear">Clear cached tiles</button><button id="seed">Seed current extent</button>
|
||||
<br>
|
||||
<p><sup>1</sup> <small>Disconnect your device from the network to test - only works for same origin layers.</small></p>
|
||||
<br>
|
||||
<div id="docs">
|
||||
<p>This example shows how to use the CacheWrite control to cache tiles
|
||||
that are being viewed in the browser's local storage, and how to use
|
||||
the CacheRead control to use cached tiles when offline or on a slow
|
||||
connection. See <a href="offline-storage.js">offline-storage.js</a>
|
||||
for the source code.</p>
|
||||
</div>
|
||||
</body>
|
||||
</html>
|
||||
@@ -0,0 +1,183 @@
|
||||
var map, cacheWrite, cacheRead1, cacheRead2;
|
||||
function init(){
|
||||
map = new OpenLayers.Map({
|
||||
div: "map",
|
||||
projection: "EPSG:900913",
|
||||
layers: [new OpenLayers.Layer.OSM("OpenStreetMap (CORS)", null, {
|
||||
eventListeners: {
|
||||
loadend: updateLayerInfo,
|
||||
tileloaded: updateTileInfo,
|
||||
tileerror: updateTileInfo
|
||||
}
|
||||
}),
|
||||
new OpenLayers.Layer.WMS("OSGeo (same origin - proxied)", "http://vmap0.tiles.osgeo.org/wms/vmap0", {
|
||||
layers: "basic"
|
||||
}, {
|
||||
eventListeners: {
|
||||
tileloadstart: function(evt) {
|
||||
// send requests through proxy
|
||||
evt.tile.url = "proxy.cgi?url=" + encodeURIComponent(evt.tile.url);
|
||||
},
|
||||
loadend: updateLayerInfo,
|
||||
tileloaded: updateTileInfo
|
||||
}
|
||||
})
|
||||
],
|
||||
center: [0,0],
|
||||
zoom: 1
|
||||
});
|
||||
cacheWrite = new OpenLayers.Control.CacheWrite({
|
||||
imageFormat: "image/jpeg",
|
||||
eventListeners: {
|
||||
cachefull: function() {
|
||||
status.innerHTML = "Cache full.";
|
||||
cacheFull = true;
|
||||
}
|
||||
}
|
||||
});
|
||||
// try cache before loading from remote resource
|
||||
cacheRead1 = new OpenLayers.Control.CacheRead({
|
||||
eventListeners: {
|
||||
activate: function() {
|
||||
cacheRead2.deactivate();
|
||||
}
|
||||
}
|
||||
});
|
||||
// try loading from remote resource and fall back to cache
|
||||
cacheRead2 = new OpenLayers.Control.CacheRead({
|
||||
autoActivate: false,
|
||||
fetchEvent: "tileerror",
|
||||
eventListeners: {
|
||||
activate: function() {
|
||||
cacheRead1.deactivate();
|
||||
}
|
||||
}
|
||||
});
|
||||
var layerSwitcher = new OpenLayers.Control.LayerSwitcher();
|
||||
map.addControls([cacheWrite, cacheRead1, cacheRead2, layerSwitcher]);
|
||||
layerSwitcher.maximizeControl();
|
||||
|
||||
// add UI and behavior
|
||||
var status = document.getElementById("status"),
|
||||
hits = document.getElementById("hits"),
|
||||
previousCount = -1,
|
||||
cacheHits = 0,
|
||||
cacheFull = false;
|
||||
updateLayerInfo();
|
||||
var read = document.getElementById("read");
|
||||
read.checked = true;
|
||||
read.onclick = toggleRead;
|
||||
var write = document.getElementById("write");
|
||||
write.checked = false;
|
||||
write.onclick = toggleWrite;
|
||||
document.getElementById("clear").onclick = clearCache;
|
||||
var tileloadstart = document.getElementById("tileloadstart");
|
||||
tileloadstart.checked = "checked";
|
||||
tileloadstart.onclick = setType;
|
||||
document.getElementById("tileerror").onclick = setType;
|
||||
document.getElementById("seed").onclick = seedCache;
|
||||
|
||||
// update the number of cached tiles and detect local storage support
|
||||
function updateLayerInfo(evt) {
|
||||
if (window.localStorage) {
|
||||
if (previousCount !== localStorage.length) {
|
||||
status.innerHTML = localStorage.length + " entries in cache.";
|
||||
}
|
||||
previousCount = localStorage.length;
|
||||
} else {
|
||||
status.innerHTML = "Local storage not supported. Try a different browser.";
|
||||
}
|
||||
}
|
||||
// update the number of cache hits and detect missing CORS support
|
||||
function updateTileInfo(evt) {
|
||||
if (cacheWrite.active) {
|
||||
try {
|
||||
var canvasContext = evt.tile.getCanvasContext();
|
||||
if (canvasContext) {
|
||||
// will throw an exception if CORS image requests are not supported
|
||||
canvasContext.canvas.toDataURL();
|
||||
} else {
|
||||
status.innerHTML = "Canvas not supported. Try a different browser.";
|
||||
}
|
||||
} catch(e) {
|
||||
status.innerHTML = "CORS image requests not supported. Try a different layer.";
|
||||
}
|
||||
}
|
||||
if (evt.tile.url.substr(0, 5) === "data:") {
|
||||
cacheHits++;
|
||||
}
|
||||
hits.innerHTML = cacheHits + " cache hits.";
|
||||
}
|
||||
|
||||
// turn the cacheRead controls on and off
|
||||
function toggleRead() {
|
||||
if (!this.checked) {
|
||||
cacheRead1.deactivate();
|
||||
cacheRead2.deactivate();
|
||||
} else {
|
||||
setType();
|
||||
}
|
||||
}
|
||||
|
||||
// turn the cacheWrite control on and off
|
||||
function toggleWrite() {
|
||||
cacheWrite[cacheWrite.active ? "deactivate" : "activate"]();
|
||||
}
|
||||
|
||||
// clear all tiles from the cache
|
||||
function clearCache() {
|
||||
OpenLayers.Control.CacheWrite.clearCache();
|
||||
cacheFull = false;
|
||||
updateLayerInfo();
|
||||
}
|
||||
|
||||
// activate the cacheRead control that matches the desired fetch strategy
|
||||
function setType() {
|
||||
if (tileloadstart.checked) {
|
||||
cacheRead1.activate();
|
||||
} else {
|
||||
cacheRead2.activate();
|
||||
}
|
||||
}
|
||||
|
||||
// seed the cache
|
||||
function seedCache() {
|
||||
var zoom = map.getZoom();
|
||||
var extent = map.getExtent();
|
||||
var center = map.getCenter();
|
||||
var active = cacheWrite.active;
|
||||
var tileWidth = map.baseLayer.tileSize.w;
|
||||
var layer = map.baseLayer;
|
||||
var buffer = layer.buffer;
|
||||
// make sure the next setCenter triggers a load
|
||||
map.zoomTo(zoom === layer.numZoomLevels-1 ? zoom - 1 : zoom + 1);
|
||||
// turn on cache writing
|
||||
cacheWrite.activate();
|
||||
// turn off cache reading
|
||||
cacheRead1.deactivate();
|
||||
cacheRead2.deactivate();
|
||||
|
||||
layer.events.register("loadend", this, function next() {
|
||||
var nextZoom = map.getZoom() + 1;
|
||||
var extentWidth = extent.getWidth() / map.getResolutionForZoom(nextZoom);
|
||||
// adjust the layer's buffer size so we don't have to pan
|
||||
layer.buffer = Math.ceil((extentWidth / tileWidth - map.getSize().w / tileWidth) / 2);
|
||||
map.zoomIn();
|
||||
if (cacheFull || nextZoom === layer.numZoomLevels-1) {
|
||||
// we're done - restore previous settings
|
||||
layer.events.unregister("loadend", this, next);
|
||||
layer.buffer = buffer;
|
||||
map.setCenter(center, zoom);
|
||||
if (!active) {
|
||||
cacheWrite.deactivate();
|
||||
}
|
||||
if (read.checked) {
|
||||
setType();
|
||||
}
|
||||
}
|
||||
});
|
||||
|
||||
// start seeding
|
||||
map.setCenter(center, zoom);
|
||||
}
|
||||
}
|
||||
Reference in New Issue
Block a user