tdf#129833 android: Allow opening files using system file picker

Extend Android Viewer with the possibility to select a file to
open using the "system file picker", which can be opened by
an Intent that has the action 'Intent.ACTION_OPEN_DOCUMENT'
(or 'Intent.ACTION_GET_CONTENT' for API level < 19) set.

This way, all locations supported by currently installed and
set up DocumentsProviders [1] are generally supported.

In a test, opening local files worked just fine, but trying
to open a file located in a NextCloud share failed
(with the corresponding app [2] installed), showing this
in ADB log:

I DownloadFileOperation: Download of /Documents/five_pages.odt to /storage/emulated/0/Android/media/com.nextcloud.client/nextcloud/<USERNAME>@demo2.nextcloud.com/Documents/five_pages.odt: Unexpected exception
E DocumentsStorageProvider: RemoteOperationResult(mSuccess=false, mHttpCode=-1, mHttpPhrase=null, mException=android.os.NetworkOnMainThreadException, mCode=HOST_NOT_AVAILABLE, message=null, getLogMessage=Unexpected exception)

This will be dealt with in a separate commit.

For now, this way to open files (and a corresponding menu
entry) is added in addition to the existing ones, but
since that method should in general be able to cover all of
the other use cases as well, the other options may be
dropped in the future.

[1] https://developer.android.com/reference/android/provider/DocumentsProvider
[2] https://github.com/nextcloud/android

Change-Id: I684a4aa770c0df7cc9fc35ff92445230405885f5
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/112768
Tested-by: Jenkins
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>

0 files changed, 0 insertions, 0 deletions