使用Cordova文件插件

Question

In my Android Cordova app I want to serve frequently used image files from a local cache in order to save bandwidth and/or when no network is available. The Cordova File plugin appears to be well suited to this job. However, I am having some difficulty establishing just how I go about creating cached image files once they have been acquired from an external source. The steps as far as I can see are the following

• Acquire the external file
• Once it is available use window.requestFileSystem to get access to the sandboxed file system. This returns the file system object which has as its filesystem attribute the object `{name:"persistent",rood:DirectoryEntry}
• Pass the directoryentry above along with the acquired image blob to fs.root.getFile('example.png', {create: true, exclusive: true},fileCreated,fileCreationFailed) ...

It is the last step that is not clear to me. From my reading of the plugin documentation the right location to create the cached image file is cache folder. However, if I were to issue the above root.getFile I would surely be attempting to create the image file in the root folder - which would probably fail because that location is not read-write.

I am either misunderstanding something here or there is a bit of documentation that is missing. In either case I hope that someone here will be able to put me on the right track.

Answer 1

As outlined in the cordova-plugin-file documentation you should be able to use the window.TEMPORARY argument when calling window.requestFileSystem get to a reference to the application cache folder which you can then use to read/write files:

window.requestFileSystem(window.TEMPORARY, 5 * 1024 * 1024, function (fs) {
    console.log('file system open: ' + fs.name);
    createFile(fs.root, "newTempFile.txt", false);
}, onErrorLoadFs);