implemented donwload upload handling with username

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

@@ -2,6 +2,12 @@ package com.dano.test1
 
 import android.content.res.Configuration
 import android.os.Bundle
+import android.view.View
+import android.widget.EditText
+import android.widget.LinearLayout
+import android.widget.ProgressBar
+import android.widget.Toast
+import androidx.appcompat.app.AlertDialog
 import androidx.appcompat.app.AppCompatActivity
 
 class MainActivity : AppCompatActivity() {
@@ -11,27 +17,112 @@ class MainActivity : AppCompatActivity() {
     var isInQuestionnaire: Boolean = false
     var isFirstQuestionnairePage: Boolean = false
 
+    private var progress: ProgressBar? = null
+
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
-        // Opening Screen nur beim echten Start initialisieren.
-        // Durch configChanges wird onCreate bei Drehung NICHT erneut aufgerufen.
-        openingScreenHandler = HandlerOpeningScreen(this)
-        openingScreenHandler.init()
+
+        // Zeige sofort Login-Dialog; erst NACH erfolgreichem Login + Download initialisieren wir den Opening Screen
+        showLoginThenDownload()
     }
 
-    // Wichtig: Bei Konfigurationsänderungen NICHT den Screen neu setzen.
-    // So bleibt man auf der aktuellen Frage/Seite.
+    private fun showLoginThenDownload() {
+        // UI mit Username/Passwort
+        val container = LinearLayout(this).apply {
+            orientation = LinearLayout.VERTICAL
+            setPadding(dp(20), dp(8), dp(20), 0)
+        }
+        val etUser = EditText(this).apply {
+            hint = "Username"
+            setSingleLine()
+        }
+        val etPass = EditText(this).apply {
+            hint = "Passwort"
+            setSingleLine()
+            inputType = android.text.InputType.TYPE_CLASS_TEXT or
+                    android.text.InputType.TYPE_TEXT_VARIATION_PASSWORD
+        }
+        container.addView(etUser)
+        container.addView(etPass)
+
+        val dialog = AlertDialog.Builder(this)
+            .setTitle("Login erforderlich")
+            .setView(container)
+            .setCancelable(false)
+            .setPositiveButton("Login") { _, _ ->
+                val user = etUser.text.toString().trim()
+                val pass = etPass.text.toString()
+                if (user.isEmpty() || pass.isEmpty()) {
+                    Toast.makeText(this, "Bitte Username & Passwort eingeben", Toast.LENGTH_SHORT).show()
+                    showLoginThenDownload()
+                    return@setPositiveButton
+                }
+                showBusy(true)
+                // Login -> Token -> Auto-Download -> OpeningScreen init
+                LoginManager.loginUserWithCredentials(
+                    context = this,
+                    username = user,
+                    password = pass,
+                    onSuccess = { token ->
+                        // optional speichern
+                        TokenStore.save(this, user, token)
+                        DatabaseDownloader.downloadAndReplaceDatabase(
+                            context = this,
+                            token = token
+                        ) { ok ->
+                            showBusy(false)
+                            if (!ok) {
+                                Toast.makeText(this, "Download fehlgeschlagen", Toast.LENGTH_LONG).show()
+                            }
+                            // Jetzt erst die Start-UI hochziehen
+                            openingScreenHandler = HandlerOpeningScreen(this)
+                            openingScreenHandler.init()
+                        }
+                    },
+                    onError = { msg ->
+                        showBusy(false)
+                        Toast.makeText(this, msg, Toast.LENGTH_LONG).show()
+                        // erneut anbieten
+                        showLoginThenDownload()
+                    }
+                )
+            }
+            .setNegativeButton("Beenden") { _, _ ->
+                finishAffinity()
+            }
+            .create()
+
+        dialog.show()
+    }
+
+    private fun showBusy(show: Boolean) {
+        if (show) {
+            if (progress == null) {
+                progress = ProgressBar(this).apply {
+                    isIndeterminate = true
+                    // simpler Vollbild-Overlay
+                    val content = window?.decorView as? android.view.ViewGroup
+                    content?.addView(this, android.view.ViewGroup.LayoutParams(
+                        android.view.ViewGroup.LayoutParams.WRAP_CONTENT,
+                        android.view.ViewGroup.LayoutParams.WRAP_CONTENT
+                    ))
+                    this.x = (resources.displayMetrics.widthPixels / 2f) - width / 2f
+                    this.y = (resources.displayMetrics.heightPixels / 2f) - height / 2f
+                }
+            }
+            progress?.visibility = View.VISIBLE
+        } else {
+            progress?.visibility = View.GONE
+        }
+    }
+
+    private fun dp(v: Int): Int = (v * resources.displayMetrics.density).toInt()
+
+    // Wichtig: Keine Neu-Initialisierung bei Rotation
     override fun onConfigurationChanged(newConfig: Configuration) {
         super.onConfigurationChanged(newConfig)
-        // Kein setContentView(), kein openingScreenHandler.init() hier!
-        // Falls du Layout-Metriken bei Rotation neu berechnen willst, kannst du das gezielt hier tun.
     }
 
-    /**
-     * Starts the given questionnaire and attaches it to this activity.
-     * @param questionnaire The questionnaire instance to start.
-     * @param languageID The language identifier for localization.
-     */
     fun startQuestionnaire(questionnaire: QuestionnaireBase<*>, languageID: String) {
         isInQuestionnaire = true
         isFirstQuestionnairePage = true
@@ -39,23 +130,17 @@ class MainActivity : AppCompatActivity() {
         questionnaire.startQuestionnaire()
     }
 
-    /**
-     * Handle the back button press.
-     * If the openingScreenHandler can handle it, do not call super.
-     * Otherwise, call the default back press behavior.
-     */
     override fun onBackPressed() {
-        if (!openingScreenHandler.onBackPressed()) {
+        if (!::openingScreenHandler.isInitialized || !openingScreenHandler.onBackPressed()) {
             super.onBackPressed()
         }
     }
 
-    /**
-     * Finish the questionnaire and return to the opening screen.
-     */
     fun finishQuestionnaire() {
         isInQuestionnaire = false
         isFirstQuestionnairePage = false
-        openingScreenHandler.init()
+        if (::openingScreenHandler.isInitialized) {
+            openingScreenHandler.init()
+        }
     }
 }