Instead of including the etag in the HTTP GET request and letting the
server set the Response Code depending on whether the etag machines, this
makes the client first issue a HEAD request, which is uses to get the etag
and the file size. We need to do the HEAD beforehand anyway to get the
file size for resumable downloads, and this approach prevents the server
from using the etag as a form of tracking cookie:
http://lucb1e.com/rp/cookielesscookies/closes#562
This caused problems when users then tried to action the pending
install, where it would no longer have enough information to install the
app. Although it may be technically possible to keep enough information
around in memory to make the app installable, but it is not worth the
effort. If a user intentionally disables a repo, we should no longer be
responsible for keeping information about its apps around.
Fixes#995.
There are some ACRA reports with this IllegalStateException getting hit.
It used to be that it was only ever because we forgot to request the
correct fields from the database. However now I'm not sure that this is
the only source. Perhaps it is also possible in response to parcelling
apk instances, or maybe something else? Either way, this should provide
further info about whether the apk doesn't belong to a repo for some
reason.
There are two methods which allow callers to choose which fields to
return. These were originally added for performance, so you only ask for
what you need. However empirically the performance gain doesn't mean
anything, because it is dwarfed by the query that was just executed.
However, it does open the code up to bugs because we forget to ask for
the right fields. So now it just returns all fields when querying for
apks.
While investigating #1086 which was about swap being busted, I
discovered that we recently introduced a worse bug when working with
multi sig stuff. The swap process, when installing an app (or even when
listening for if a user started installing - before they even did
anything), would ask for an apk from any repo. This is wrong, because we
should only ask for the apks from the swap repo when presented with a
swap dialog.
By fixing this so that it asks for a specific apk, this may also
fix the issue in #1086, because that was about us not asking for enough
info from the database for each Apk which was returned. Now we just
return all columns, because the performance overhead should be minimal,
but it prevents this class of bugs, where we didn't fully populate
our value object. However, I'm not confident that it is fixed, because I
was unable to reproduce it due to the other crash fixed in this change.
Relevant crash:
```
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String org.fdroid.fdroid.data.Apk.getUrl()' on a null object reference
at org.fdroid.fdroid.views.swap.SwapAppsView$AppListAdapter$ViewHolder.setApp(SwapAppsView.java:311)
at org.fdroid.fdroid.views.swap.SwapAppsView$AppListAdapter.bindView(SwapAppsView.java:422)
at org.fdroid.fdroid.views.swap.SwapAppsView$AppListAdapter.newView(SwapAppsView.java:414)
at android.support.v4.widget.CursorAdapter.getView(CursorAdapter.java:269)
at android.widget.AbsListView.obtainView(AbsListView.java:2349)
at android.widget.ListView.makeAndAddView(ListView.java:1864)
at android.widget.ListView.fillDown(ListView.java:698)
...
```
