Unify the usage of cursors

Safer and less error-prone because:

* Always checks for null
* Checks for sizes
* Inits App/Apk lists at known capacity
* Properly closes all cursors

There are still one or two cursors that are not closed correctly and show
things like these:

W/CursorWrapperInner(19973): Cursor finalized without prior close()

src/org/fdroid/fdroid/UpdateService.java

@@ -539,6 +539,7 @@ public class UpdateService extends IntentService implements ProgressListener {
 
         int knownIdCount = cursor != null ? cursor.getCount() : 0;
         List<String> knownIds = new ArrayList<String>(knownIdCount);
+        if (cursor != null) {
             if (knownIdCount > 0) {
                 cursor.moveToFirst();
                 while (!cursor.isAfterLast()) {
@@ -546,6 +547,8 @@ public class UpdateService extends IntentService implements ProgressListener {
                     cursor.moveToNext();
                 }
             }
+            cursor.close();
+        }
 
         return knownIds;
     }

src/org/fdroid/fdroid/data/ApkProvider.java

@@ -32,13 +32,16 @@ public class ApkProvider extends FDroidProvider {
         }
 
         public static List<Apk> cursorToList(Cursor cursor) {
-            List<Apk> apks = new ArrayList<Apk>();
+            int knownApkCount = cursor != null ? cursor.getCount() : 0;
+            List<Apk> apks = new ArrayList<Apk>(knownApkCount);
             if (cursor != null) {
+                if (knownApkCount > 0) {
                     cursor.moveToFirst();
                     while (!cursor.isAfterLast()) {
                         apks.add(new Apk(cursor));
                         cursor.moveToNext();
                     }
+                }
                 cursor.close();
             }
             return apks;
@@ -64,12 +67,15 @@ public class ApkProvider extends FDroidProvider {
             ContentResolver resolver = context.getContentResolver();
             Uri uri = getContentUri(id, versionCode);
             Cursor cursor = resolver.query(uri, projection, null, null, null);
-            if (cursor != null && cursor.getCount() > 0) {
+            Apk apk = null;
+            if (cursor != null) {
+                if (cursor.getCount() > 0) {
                     cursor.moveToFirst();
-                return new Apk(cursor);
+                    apk = new Apk(cursor);
-            } else {
-                return null;
                 }
+                cursor.close();
+            }
+            return apk;
         }
 
         public static List<Apk> findByApp(Context context, String appId) {

src/org/fdroid/fdroid/data/AppProvider.java

@@ -40,13 +40,16 @@ public class AppProvider extends FDroidProvider {
         }
 
         private static List<App> cursorToList(Cursor cursor) {
-            List<App> apps = new ArrayList<App>();
+            int knownAppCount = cursor != null ? cursor.getCount() : 0;
+            List<App> apps = new ArrayList<App>(knownAppCount);
             if (cursor != null) {
+                if (knownAppCount > 0) {
                     cursor.moveToFirst();
                     while (!cursor.isAfterLast()) {
                         apps.add(new App(cursor));
                         cursor.moveToNext();
                     }
+                }
                 cursor.close();
             }
             return apps;
@@ -71,6 +74,7 @@ public class AppProvider extends FDroidProvider {
             Cursor cursor = resolver.query(uri, projection, null, null, null );
             Set<String> categorySet = new HashSet<String>();
             if (cursor != null) {
+                if (cursor.getCount() > 0) {
                     cursor.moveToFirst();
                     while (!cursor.isAfterLast()) {
                         String categoriesString = cursor.getString(0);
@@ -82,6 +86,8 @@ public class AppProvider extends FDroidProvider {
                         cursor.moveToNext();
                     }
                 }
+                cursor.close();
+            }
             List<String> categories = new ArrayList<String>(categorySet);
             Collections.sort(categories);
 
@@ -103,12 +109,15 @@ public class AppProvider extends FDroidProvider {
                                    String[] projection) {
             Uri uri = getContentUri(appId);
             Cursor cursor = resolver.query(uri, projection, null, null, null);
-            if (cursor != null && cursor.getCount() > 0) {
+            App app = null;
+            if (cursor != null) {
+                if (cursor.getCount() > 0) {
                     cursor.moveToFirst();
-                return new App(cursor);
+                    app = new App(cursor);
-            } else {
-                return null;
                 }
+                cursor.close();
+            }
+            return app;
         }
 
         public static void deleteAppsWithNoApks(ContentResolver resolver) {

src/org/fdroid/fdroid/data/DBHelper.java

@@ -102,6 +102,7 @@ public class DBHelper extends SQLiteOpenHelper {
             String[] columns = { "address", "_id" };
             Cursor cursor = db.query(TABLE_REPO, columns,
                     "name IS NULL OR name = ''", null, null, null, null);
+            if (cursor != null) {
                 if (cursor.getCount() > 0) {
                     cursor.moveToFirst();
                     while (!cursor.isAfterLast()) {
@@ -116,6 +117,8 @@ public class DBHelper extends SQLiteOpenHelper {
                         cursor.moveToNext();
                     }
                 }
+                cursor.close();
+            }
         }
     }
 
@@ -254,19 +257,23 @@ public class DBHelper extends SQLiteOpenHelper {
     private void migrateRepoTable(SQLiteDatabase db, int oldVersion) {
         if (oldVersion < 20) {
             List<Repo> oldrepos = new ArrayList<Repo>();
-            Cursor c = db.query(TABLE_REPO,
+            Cursor cursor = db.query(TABLE_REPO,
                     new String[] { "address", "inuse", "pubkey" },
                     null, null, null, null, null);
-            c.moveToFirst();
+            if (cursor != null) {
-            while (!c.isAfterLast()) {
+                if (cursor.getCount() > 0) {
+                    cursor.moveToFirst();
+                    while (!cursor.isAfterLast()) {
                         Repo repo = new Repo();
-                repo.address = c.getString(0);
+                        repo.address = cursor.getString(0);
-                repo.inuse = (c.getInt(1) == 1);
+                        repo.inuse = (cursor.getInt(1) == 1);
-                repo.pubkey = c.getString(2);
+                        repo.pubkey = cursor.getString(2);
                         oldrepos.add(repo);
-                c.moveToNext();
+                        cursor.moveToNext();
+                    }
+                }
+                cursor.close();
             }
-            c.close();
             db.execSQL("drop table " + TABLE_REPO);
             db.execSQL(CREATE_TABLE_REPO);
             for (Repo repo : oldrepos) {
@@ -316,18 +323,22 @@ public class DBHelper extends SQLiteOpenHelper {
             if (!columnExists(db, TABLE_REPO, "fingerprint"))
                 db.execSQL("alter table " + TABLE_REPO + " add column fingerprint text");
             List<Repo> oldrepos = new ArrayList<Repo>();
-            Cursor c = db.query(TABLE_REPO,
+            Cursor cursor = db.query(TABLE_REPO,
                     new String[] { "address", "pubkey" },
                     null, null, null, null, null);
-            c.moveToFirst();
+            if (cursor != null) {
-            while (!c.isAfterLast()) {
+                if (cursor.getCount() > 0) {
+                    cursor.moveToFirst();
+                    while (!cursor.isAfterLast()) {
                         Repo repo = new Repo();
-                repo.address = c.getString(0);
+                        repo.address = cursor.getString(0);
-                repo.pubkey = c.getString(1);
+                        repo.pubkey = cursor.getString(1);
                         oldrepos.add(repo);
-                c.moveToNext();
+                        cursor.moveToNext();
+                    }
+                }
+                cursor.close();
             }
-            c.close();
             for (Repo repo : oldrepos) {
                 ContentValues values = new ContentValues();
                 values.put("fingerprint", Utils.calcFingerprint(repo.pubkey));

src/org/fdroid/fdroid/data/RepoProvider.java

@@ -33,6 +33,7 @@ public class RepoProvider extends FDroidProvider {
             if (cursor != null) {
                 cursor.moveToFirst();
                 repo = new Repo(cursor);
+                cursor.close();
             }
             return repo;
         }
@@ -176,13 +177,16 @@ public class RepoProvider extends FDroidProvider {
             ContentResolver resolver = context.getContentResolver();
             String[] projection = { ApkProvider.DataColumns._COUNT_DISTINCT_ID };
             Uri apkUri = ApkProvider.getRepoUri(repoId);
-            Cursor result = resolver.query(apkUri, projection, null, null, null);
+            Cursor cursor = resolver.query(apkUri, projection, null, null, null);
-            if (result != null && result.getCount() > 0) {
+            int count = 0;
-                result.moveToFirst();
+            if (cursor != null) {
-                return result.getInt(0);
+                if (cursor.getCount() > 0) {
-            } else {
+                    cursor.moveToFirst();
-                return 0;
+                    count = cursor.getInt(0);
                 }
+                cursor.close();
+            }
+            return count;
         }
     }