Updater: No need to install every update

* Apparently users are not aware that they don't have to install every
  update we ever released (weeklies) after they have skipped some due
  to various reasons
* Since we are providing full installation packages, remind the user that
  it's ok to only ever choose the newest one

Change-Id: I70f9acd70344f36aaae7e45b848f6bcb7a8b3c0f

res/values/strings.xml

@@ -152,4 +152,8 @@
     <string name="new_updates_channel_title">New updates</string>
     <string name="ongoing_channel_title">Ongoing downloads</string>
     <string name="update_failed_channel_title">Update failed</string>
+
+    <string name="info_dialog_title">Did you know?</string>
+    <string name="info_dialog_message">LineageOS updates are full installation packages. That means you can always install only the latest update, even if you skipped some in between!</string>
+    <string name="info_dialog_ok">Thanks for the info!</string>
 </resources>

src/org/lineageos/updater/UpdatesListAdapter.java

@@ -477,7 +477,10 @@ public class UpdatesListAdapter extends RecyclerView.Adapter<UpdatesListAdapter.
                 .setMessage(mActivity.getString(resId, buildInfoText,
                         mActivity.getString(android.R.string.ok)))
                 .setPositiveButton(android.R.string.ok,
-                        (dialog, which) -> Utils.triggerUpdate(mActivity, downloadId))
+                        (dialog, which) -> {
+                            Utils.triggerUpdate(mActivity, downloadId);
+                            maybeShowInfoDialog();
+                        })
                 .setNegativeButton(android.R.string.cancel, null);
     }
 
@@ -493,6 +496,21 @@ public class UpdatesListAdapter extends RecyclerView.Adapter<UpdatesListAdapter.
                 .setNegativeButton(android.R.string.cancel, null);
     }
 
+    private void maybeShowInfoDialog() {
+        SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(mActivity);
+        boolean alreadySeen = preferences.getBoolean(Constants.HAS_SEEN_INFO_DIALOG, false);
+        if (alreadySeen) {
+            return;
+        }
+        new AlertDialog.Builder(mActivity)
+                .setTitle(R.string.info_dialog_title)
+                .setMessage(R.string.info_dialog_message)
+                .setPositiveButton(R.string.info_dialog_ok, (dialog, which) -> preferences.edit()
+                        .putBoolean(Constants.HAS_SEEN_INFO_DIALOG, true)
+                        .apply())
+                .show();
+    }
+
     private void startActionMode(final UpdateInfo update, final boolean canDelete, View anchor) {
         mSelectedDownload = update.getDownloadId();
         notifyItemChanged(update.getDownloadId());

src/org/lineageos/updater/misc/Constants.java

@@ -55,4 +55,6 @@ public final class Constants {
 
     public static final String UPDATE_RECOVERY_EXEC = "/vendor/bin/install-recovery.sh";
     public static final String UPDATE_RECOVERY_PROPERTY = "persist.vendor.recovery_update";
+
+    public static final String HAS_SEEN_INFO_DIALOG = "has_seen_info_dialog";
 }