适用于 iPad 的 Openlayers 离线缓存
我正在为 iPad 构建一个 HTML5 应用程序，它将包含一个用于基本上下文信息的地图。我需要某种方法来有选择地离线缓存地图（即我要去一个我知道没有连接的区域，所以让我预先缓存地图的该部分）。
或者，我可以从它们的 WebSQL 存储库渲染矢量图层，在这种情况下，我如何将地图转换为矢量并在平移地图中显示这些矢量（即在矢量图层之间交换或添加矢量层）
提前致谢
I am building an HTML5 app for an iPad and it will contain a map for basic contextual information. I need some way to cache the map offline selectively (i.e. I am going to an area that I know is without connectivity so let me cache that part of the map beforehand).
Alternatively I can render vector layers from a WebSQL repository of them and in that case how would I convert maps to vector and display these vectors in a panning map (i.e. Swap between or add too vector layers)
Thanks in advance
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我知道一些人在二月份的 OpenLayers Mobile Codesprint 期间正在尝试本地存储支持。 这是他们的示例完成了。我建议您查看 jgrocha 的沙箱，看看他们所做的是否适合您需要。
I know that some guys were experimenting on local storage support during OpenLayers Mobile Codesprint back in February. Here is an example of what they've accomplished. I recommend that you checkout jgrocha's sandbox and take a look if what they did suits your needs.
看起来 touchMapLite 有一些离线缓存功能。我还没有深入研究它来看看它的工作效果如何（或是否），但您可以在代码中看到有填充和检索缓存地图图块的示例
http://sourceforge.net/projects/touchmaplite/
Looks like touchMapLite has some offline caching features. I have not dug too far into it to see how well (or if) it works, but you can see in the code that there are examples of populating and retrieving cached map tiles
http://sourceforge.net/projects/touchmaplite/
我使用 cloudmade tms 层并结合 openlayers 沙箱的一些灵感来完成此操作。
简而言之，您必须将图层的 async 属性设置为 true 并为该图层提供 getURLasync 方法。在此方法中，您可以检查图层是否位于本地存储/网络数据库中，否则从网络加载图块。
getURLasync 方法将图像作为属性，用户可以将其转换为 dataurl 字符串，如果脱机缓存中不存在图块，则需要使用该字符串来存储图块。
您可以在这里找到一些示例代码：
http://allartk.nl/content/html5-offline-mapping
I've done this using a cloudmade tms layer togeteher with some inspiration from the openlayers sandboxes.
In short, you've to set the async property of an layer to true and provide a getURLasync method for that layer. In this method you can check if the layer is in a local storage / webdatabase and else load the tile from the web.
The getURLasync method has the image as property wich can be user to convert it to a dataurl string, which is needed to store the tile if not present in the offline cache.
You can find some example code here:
http://allartk.nl/content/html5-offline-mapping
我使用过一款名为 OffMaps 的 iPod touch 应用程序。它会缓存您直接在 iPod 上看到的所有内容，然后您可以稍后在没有 Wi-Fi 时使用地图程序，并且这些图块仍然存在。不知道他们是如何做到的，但事实证明这是可能的。
I have used an ipod touch app called OffMaps. It caches everything you look at directly on the ipod, then you can use the map program later when not on wifi and those tiles are still there. No idea how they did it, but it proves its possible.