added deltaUpload but not working 100% in combination with fullUpload. Changed download, it is now deleting the existing database before downloading.

app/src/main/java/com/dano/test1/DatabaseDownloader.kt

@@ -21,6 +21,16 @@ object DatabaseDownloader {
     fun downloadAndReplaceDatabase(context: Context) {
         CoroutineScope(Dispatchers.IO).launch {
             try {
+                // Alte DB sofort löschen, bevor irgendwas heruntergeladen wird
+                val dbFile = context.getDatabasePath(DB_NAME)
+                if (dbFile.exists()) {
+                    if (dbFile.delete()) {
+                        Log.d("DOWNLOAD", "Bestehende lokale DB gelöscht.")
+                    } else {
+                        Log.e("DOWNLOAD", "Konnte bestehende DB nicht löschen.")
+                    }
+                }
+
                 Log.d("DOWNLOAD", "Download gestartet: $SERVER_DOWNLOAD_URL")
 
                 val request = Request.Builder()
@@ -41,10 +51,7 @@ object DatabaseDownloader {
                 }
                 Log.d("DOWNLOAD", "Datei gespeichert: ${downloadedFile.absolutePath}")
 
-                val dbFile = context.getDatabasePath(DB_NAME)
-                if (dbFile.exists()) dbFile.delete()
                 downloadedFile.copyTo(dbFile, overwrite = true)
-
                 Log.d("DOWNLOAD", "Neue DB erfolgreich eingesetzt")
 
             } catch (e: Exception) {

app/src/main/java/com/dano/test1/DatabaseUploader.kt

@@ -2,13 +2,17 @@ package com.dano.test1
 
 import android.content.Context
 import android.database.sqlite.SQLiteDatabase
+import android.util.Base64
 import android.util.Log
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.launch
+import android.database.Cursor
 import okhttp3.*
 import okhttp3.MediaType.Companion.toMediaTypeOrNull
 import okhttp3.RequestBody.Companion.asRequestBody
+import org.json.JSONArray
+import org.json.JSONObject
 import java.io.File
 import java.io.IOException
 import kotlin.system.exitProcess
@@ -16,7 +20,9 @@ import kotlin.system.exitProcess
 object DatabaseUploader {
 
     private const val DB_NAME = "questionnaire_database"
-    private const val SERVER_UPLOAD_URL = "http://49.13.157.44/uploadFull.php"
+    private const val SERVER_FULL_URL = "http://49.13.157.44/uploadFull.php"
+    private const val SERVER_DELTA_URL = "http://49.13.157.44/uploadDelta.php"
+    private const val SERVER_CHECK_URL = "http://49.13.157.44/checkDatabaseExists.php"
     private const val API_TOKEN = "MEIN_SUPER_GEHEIMES_TOKEN_12345"
 
     private val client = OkHttpClient()
@@ -30,21 +36,34 @@ object DatabaseUploader {
                     return@launch
                 }
 
-                // WAL-Daten in die Hauptdatei schreiben
+                // WAL-Checkpoint
                 try {
                     val db = SQLiteDatabase.openDatabase(
                         dbFile.absolutePath,
                         null,
                         SQLiteDatabase.OPEN_READWRITE
                     )
-                    db.execSQL("PRAGMA wal_checkpoint(FULL);")
+                    db.rawQuery("PRAGMA wal_checkpoint(FULL);", null).use { cursor ->
+                        if (cursor.moveToFirst()) {
+                            try {
+                                Log.d("UPLOAD", "WAL-Checkpoint result: ${cursor.getInt(0)}")
+                            } catch (_: Exception) {}
+                        }
+                    }
                     db.close()
-                    Log.d("UPLOAD", "WAL-Checkpoint erfolgreich durchgeführt.")
+                    Log.d("UPLOAD", "WAL-Checkpoint erfolgreich.")
                 } catch (e: Exception) {
                     Log.e("UPLOAD", "Fehler beim WAL-Checkpoint", e)
                 }
 
-                uploadFile(dbFile)
+                val exists = checkDatabaseExists()
+                if (exists) {
+                    Log.d("UPLOAD", "Server-Datenbank vorhanden → Delta-Upload")
+                    uploadDelta(dbFile)
+                } else {
+                    Log.d("UPLOAD", "Keine Server-Datenbank → Full-Upload")
+                    uploadFull(dbFile)
+                }
 
             } catch (e: Exception) {
                 Log.e("UPLOAD", "Fehler beim Hochladen der DB", e)
@@ -52,7 +71,33 @@ object DatabaseUploader {
         }
     }
 
-    private fun uploadFile(file: File) {
+    private fun checkDatabaseExists(): Boolean {
+        return try {
+            val request = Request.Builder()
+                .url(SERVER_CHECK_URL)
+                .get()
+                .build()
+
+            client.newCall(request).execute().use { response ->
+                if (!response.isSuccessful) {
+                    Log.e("UPLOAD", "checkDatabaseExists HTTP error: ${response.code}")
+                    return false
+                }
+                val body = response.body?.string() ?: return false
+                try {
+                    val j = JSONObject(body)
+                    j.optBoolean("exists", false)
+                } catch (e: Exception) {
+                    body.contains("exists", ignoreCase = true)
+                }
+            }
+        } catch (e: Exception) {
+            Log.e("UPLOAD", "Fehler bei Server-Prüfung", e)
+            false
+        }
+    }
+
+    private fun uploadFull(file: File) {
         val requestBody = MultipartBody.Builder()
             .setType(MultipartBody.FORM)
             .addFormDataPart(
@@ -63,28 +108,94 @@ object DatabaseUploader {
             .build()
 
         val request = Request.Builder()
-            .url(SERVER_UPLOAD_URL)
+            .url(SERVER_FULL_URL)
             .post(requestBody)
             .build()
 
-        client.newCall(request).enqueue(object : Callback {
+        client.newCall(request).enqueue(serverCallback(file))
-            override fun onFailure(call: Call, e: IOException) {
+    }
-                Log.e("UPLOAD", "Upload fehlgeschlagen: ${e.message}")
+
+    private fun uploadDelta(file: File) {
+        try {
+            val db = SQLiteDatabase.openDatabase(file.absolutePath, null, SQLiteDatabase.OPEN_READONLY)
+
+            val data = JSONObject().apply {
+                put("clients", queryToJsonArray(db, "SELECT clientCode FROM clients"))
+                put("questionnaires", queryToJsonArray(db, "SELECT id FROM questionnaires"))
+                put("questions", queryToJsonArray(db, "SELECT questionId, questionnaireId, question FROM questions"))
+                put("answers", queryToJsonArray(db, "SELECT clientCode, questionId, answerValue FROM answers"))
+                put("completed_questionnaires",
+                    queryToJsonArray(db, "SELECT clientCode, questionnaireId, timestamp, isDone, sumPoints FROM completed_questionnaires")
+                )
             }
 
-            override fun onResponse(call: Call, response: Response) {
+            db.close()
-                if (response.isSuccessful) {
+
-                    Log.d("UPLOAD", "Upload erfolgreich: ${response.message}")
+            val requestBody = MultipartBody.Builder()
-                    if (file.delete()) {
+                .setType(MultipartBody.FORM)
-                        Log.d("UPLOAD", "Lokale DB gelöscht.")
+                .addFormDataPart("token", API_TOKEN)
-                        exitProcess(0)
+                .addFormDataPart("data", data.toString())
-                    } else {
+                .build()
-                        Log.e("UPLOAD", "Löschen der lokalen DB fehlgeschlagen.")
+
+            val request = Request.Builder()
+                .url(SERVER_DELTA_URL)
+                .post(requestBody)
+                .build()
+
+            client.newCall(request).enqueue(serverCallback(file))
+
+        } catch (e: Exception) {
+            Log.e("UPLOAD", "Fehler beim Delta-Upload", e)
+        }
+    }
+
+    private fun queryToJsonArray(db: SQLiteDatabase, query: String): JSONArray {
+        val cursor = db.rawQuery(query, null)
+        val jsonArray = JSONArray()
+        cursor.use {
+            val columnNames = it.columnNames
+            while (it.moveToNext()) {
+                val obj = JSONObject()
+                for (col in columnNames) {
+                    val idx = it.getColumnIndex(col)
+                    if (idx >= 0) {
+                        when (it.getType(idx)) {
+                            Cursor.FIELD_TYPE_INTEGER -> obj.put(col, it.getLong(idx))
+                            Cursor.FIELD_TYPE_FLOAT -> obj.put(col, it.getDouble(idx))
+                            Cursor.FIELD_TYPE_STRING -> obj.put(col, it.getString(idx))
+                            Cursor.FIELD_TYPE_NULL -> obj.put(col, JSONObject.NULL)
+                            Cursor.FIELD_TYPE_BLOB -> {
+                                val blob = it.getBlob(idx)
+                                obj.put(col, Base64.encodeToString(blob, Base64.NO_WRAP))
+                            }
+                            else -> obj.put(col, it.getString(idx))
+                        }
                     }
-                } else {
-                    Log.e("UPLOAD", "Upload fehlgeschlagen: ${response.code} ${response.message}")
                 }
+                jsonArray.put(obj)
             }
-        })
+        }
+        return jsonArray
+    }
+
+    private fun serverCallback(file: File) = object : Callback {
+        override fun onFailure(call: Call, e: IOException) {
+            Log.e("UPLOAD", "Upload fehlgeschlagen: ${e.message}")
+        }
+
+        override fun onResponse(call: Call, response: Response) {
+            val body = try { response.body?.string() ?: "Keine Response" } catch (e: Exception) { "Fehler beim Lesen der Response: ${e.message}" }
+            if (response.isSuccessful) {
+                Log.d("UPLOAD", "Upload erfolgreich: $body")
+                if (file.delete()) {
+                    Log.d("UPLOAD", "Lokale DB gelöscht.")
+                    exitProcess(0)
+                } else {
+                    Log.e("UPLOAD", "Löschen der lokalen DB fehlgeschlagen.")
+                }
+            } else {
+                Log.e("UPLOAD", "Upload fehlgeschlagen: ${response.code} $body")
+            }
+        }
     }
 }