Check downloaded apks on F-Droid first start.

This will read downloaded .apk files from the disk cache in the background.
For each apk that corresponds to an app which can be updated, the status
manager is notified.

app/src/main/AndroidManifest.xml

@@ -297,6 +297,9 @@
         <service
             android:name=".data.InstalledAppProviderService"
             android:exported="false" />
+        <service
+            android:name=".AppUpdateStatusService"
+            android:exported="false" />
 
         <activity android:name=".views.main.MainActivity">
             <intent-filter>

app/src/main/java/org/fdroid/fdroid/AppUpdateStatusManager.java

@@ -40,6 +40,7 @@ public final class AppUpdateStatusManager {
      *  * The user clears the list of installed apps from notification manager.
      *  * The user clears the list of apps available to update from the notification manager.
      *  * A repo update is completed and a bunch of new apps are ready to be updated.
+     *  * F-Droid is opened, and it finds a bunch of .apk files downloaded and ready to install.
      */
     public static final String BROADCAST_APPSTATUS_LIST_CHANGED = "org.fdroid.fdroid.installer.appstatus.listchange";
 

app/src/main/java/org/fdroid/fdroid/AppUpdateStatusService.java

@@ -0,0 +1,54 @@
+package org.fdroid.fdroid;
+
+import android.app.IntentService;
+import android.content.Context;
+import android.content.Intent;
+import android.net.Uri;
+import android.support.annotation.Nullable;
+
+import org.fdroid.fdroid.data.Apk;
+import org.fdroid.fdroid.data.ApkProvider;
+import org.fdroid.fdroid.data.App;
+import org.fdroid.fdroid.data.AppProvider;
+import org.fdroid.fdroid.data.Schema;
+import org.fdroid.fdroid.installer.ApkCache;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Scans the list of downloaded .apk files in the cache for each app which can be updated.
+ * If a valid .apk file is found then it will tell the {@link AppUpdateStatusManager} that it is
+ * {@link AppUpdateStatusManager.Status#ReadyToInstall}. This is an {@link IntentService} so as to
+ * run on a background thread, as it hits the disk a bit to figure out the hash of each downloaded
+ * file.
+ */
+public class AppUpdateStatusService extends IntentService {
+
+    /**
+     * Queue up a background scan of all downloaded apk files to see if we should notify the user
+     * that they are ready to install.
+     */
+    public static void scanDownloadedApks(Context context) {
+        context.startService(new Intent(context, AppUpdateStatusService.class));
+    }
+
+    public AppUpdateStatusService() {
+        super("AppUpdateStatusService");
+    }
+
+    @Override
+    protected void onHandleIntent(@Nullable Intent intent) {
+        List<App> apps = AppProvider.Helper.findCanUpdate(this, Schema.AppMetadataTable.Cols.ALL);
+        List<Apk> apksReadyToInstall = new ArrayList<>();
+        for (App app : apps) {
+            Apk apk = ApkProvider.Helper.findApkFromAnyRepo(this, app.packageName, app.suggestedVersionCode);
+            Uri downloadUri = Uri.parse(apk.getUrl());
+            if (ApkCache.apkIsCached(ApkCache.getApkDownloadPath(this, downloadUri), apk)) {
+                apksReadyToInstall.add(apk);
+            }
+        }
+
+        AppUpdateStatusManager.getInstance(this).addApks(apksReadyToInstall, AppUpdateStatusManager.Status.ReadyToInstall);
+    }
+}

app/src/main/java/org/fdroid/fdroid/FDroidApp.java

@@ -234,6 +234,7 @@ public class FDroidApp extends Application {
         Preferences.get().configureProxy();
 
         InstalledAppProviderService.compareToPackageManager(this);
+        AppUpdateStatusService.scanDownloadedApks(this);
 
         // If the user changes the preference to do with filtering rooted apps,
         // it is easier to just notify a change in the app provider,