use a Drawercontext to be able to have a specific scaffold for each page

lib/db/database.dart

@@ -28,7 +28,7 @@ class Db {
       // Set the path to the database. Note: Using the `join` function from the
       // `path` package is best practice to ensure the path is correctly
       // constructed for each platform.
-      join(await getDatabasesPath(), 'previews.db'),
+      dbpath,
       onCreate: (db, version) {
         // Run the CREATE TABLE statement on the database.
         return db.execute(
@@ -41,6 +41,22 @@ class Db {
     );
   }
 
+  /// delete all data but keep structure
+  Future<void> clear() async {
+    await _db.delete("previews");
+    // shrink the db file size
+    await _db.execute("VACUUM");
+  }
+
+  /// get db size in bytes
+  Future<int> getDbSize() async {
+    final int cnt = (await Db().db().rawQuery("pragma page_count;"))[0]
+    ["page_count"] as int;
+    final int pagesize =
+    (await Db().db().rawQuery("pragma page_size;"))[0]["page_size"] as int;
+    return cnt * pagesize;
+  }
+
   Database db() {
     return _db;
   }