android - How to access external storage with cordova file / file-system-roots plugins?

Question

Problem description: I can access the internal storage with either the file or the file-system-roots (read and write). But such a file can not be access from an other app. For example if I want to send this file through the emailComposerPlugin, the file can not be accessed by the email client. (Same goes for the "open with" function.) If I change the options {sandboxed: true} to false (to write to the external storage), it does not work and ends up in a FileUtils.UNKNOWN_ERR. I tried the application while the phone disconnected from USB, as some docs mentioned that external storage can not be accessed while mounted on the pc - same result though.

From what I read on the mailing list this should be possible. It seems I miss a crucial point?

Context: I try to enable an hybrid application created for iPhone to run on android devices. To have a little playground, I create a small test project.

Edit: There seems to be a problem between file-system-roots and file plugin. But I have the newest versions of both of them. (File: 1.0.1 File-system-roots: 0.1.0) Debugging the file-system and file classes show that

private String fullPathForLocalURL(Uri URL) {
    if (FILESYSTEM_PROTOCOL.equals(URL.getScheme()) && "localhost".equals(URL.getHost())) {
        String path = URL.getPath();
        if (URL.getQuery() != null) {
            path = path + "?" + URL.getQuery();
        }
        return path.substring(path.indexOf('/', 1));
        // path = "/cache-external" at this point
        // results in index out of bounds exception

What have I tried?

config.xml

<preference name="AndroidExtraFilesystems" value="files,files-external,documents,sdcard,cache,cache-external" />

AndroidManifest.xml

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

javascript code

function createTextDocument(filename, text) {

    cordova.filesystem.getDirectoryForPurpose('cache', {sandboxed: false}, successCallback, failureCallback);

    function successCallback(directoryEntry){
        console.log('directory found (cordova): ' + directoryEntry.toURL());
        console.log('directory found (native) : ' + directoryEntry.toNativeURL());
        directoryEntry.getFile(filename, {create: true, exclusive: false},
            function(fileEntry){
                var filePath = fileEntry.toNativeURL();
                fileEntry.createWriter(
                    function(fileWriter){
                        console.log('start writing to: ' + filePath );
                        fileWriter.write(text);
                        console.log('file written');
                    },failureCallback
                );
            }, failureCallback
        );
    }

    function failureCallback(error){
        console.log('error creating file: ' + error.code);
        // results in code 1000
    }
}

Answer 1

After digging this whole topic quite a bit, i figured out:

• There is no need for the file system roots plugin.
• There is more configuration needed in config.xml.
• You need to use not the standard FileApi way, but the following to access the files.

JavaScript usage:

window.resolveLocalFileSystemURL(path, cbSuccess, cbFail);

@param path: {string} a cordova path with scheme: 
             'cdvfile://localhost/<file-system-name>/<path-to-file>' 
             Examples: 'cdvfile://localhost/sdcard/path/to/global/file'
                       'cdvfile://localhost/cache/onlyVisibleToTheApp.txt'
@param cbSuccess: {function} a callback method that receives a DirectoryEntry object.
@param cbFail: {function} a callback method that receives a FileError object.

config.xml

<preference name="AndroidPersistentFileLocation" value="Compatibility" />
<preference name="AndroidExtraFilesystems" value="sdcard,cache" />

AndroidManifest.xml

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />