diff --git a/common/src/commonMain/kotlin/net/dankito/utils/multiplatform/ObjectHolder.kt b/common/src/commonMain/kotlin/net/dankito/utils/multiplatform/ObjectHolder.kt
new file mode 100644
index 00000000..093646da
--- /dev/null
+++ b/common/src/commonMain/kotlin/net/dankito/utils/multiplatform/ObjectHolder.kt
@@ -0,0 +1,12 @@
+package net.dankito.utils.multiplatform
+
+
+open class ObjectHolder<T>(
+    var value: T
+) {
+
+    override fun toString(): String {
+        return value?.toString() ?: "Value is null"
+    }
+
+}
\ No newline at end of file
diff --git a/fints4k/src/commonMain/kotlin/net/dankito/banking/fints/tan/FlickerCodeStepsCalculator.kt b/fints4k/src/commonMain/kotlin/net/dankito/banking/fints/tan/FlickerCodeStepsCalculator.kt
index 0aad576f..e174edcf 100644
--- a/fints4k/src/commonMain/kotlin/net/dankito/banking/fints/tan/FlickerCodeStepsCalculator.kt
+++ b/fints4k/src/commonMain/kotlin/net/dankito/banking/fints/tan/FlickerCodeStepsCalculator.kt
@@ -1,42 +1,46 @@
 package net.dankito.banking.fints.tan
 
-
-open class FlickerCodeStepsCalculator(var code: String) {
-
-    var halfbyteid = 0
-    var clock = Bit.High
-    var bitarray = mutableListOf<MutableList<Bit>>()
-
-    val steps: List<Array<Bit>>
+import net.dankito.utils.multiplatform.ObjectHolder
 
 
-    fun reset() {
-        halfbyteid = 0
-        clock = Bit.High
+open class FlickerCodeStepsCalculator {
+
+    companion object {
+
+        val bits = mutableMapOf<Char, List<Bit>>()
+
+        init {
+            /* bitfield: clock, bits 2^1, 2^2, 2^3, 2^4 */
+            bits['0'] = listOf(Bit.Low, Bit.Low, Bit.Low, Bit.Low, Bit.Low)
+            bits['1'] = listOf(Bit.Low, Bit.High, Bit.Low, Bit.Low, Bit.Low)
+            bits['2'] = listOf(Bit.Low, Bit.Low, Bit.High, Bit.Low, Bit.Low)
+            bits['3'] = listOf(Bit.Low, Bit.High, Bit.High, Bit.Low, Bit.Low)
+            bits['4'] = listOf(Bit.Low, Bit.Low, Bit.Low, Bit.High, Bit.Low)
+            bits['5'] = listOf(Bit.Low, Bit.High, Bit.Low, Bit.High, Bit.Low)
+            bits['6'] = listOf(Bit.Low, Bit.Low, Bit.High, Bit.High, Bit.Low)
+            bits['7'] = listOf(Bit.Low, Bit.High, Bit.High, Bit.High, Bit.Low)
+            bits['8'] = listOf(Bit.Low, Bit.Low, Bit.Low, Bit.Low, Bit.High)
+            bits['9'] = listOf(Bit.Low, Bit.High, Bit.Low, Bit.Low, Bit.High)
+            bits['A'] = listOf(Bit.Low, Bit.Low, Bit.High, Bit.Low, Bit.High)
+            bits['B'] = listOf(Bit.Low, Bit.High, Bit.High, Bit.Low, Bit.High)
+            bits['C'] = listOf(Bit.Low, Bit.Low, Bit.Low, Bit.High, Bit.High)
+            bits['D'] = listOf(Bit.Low, Bit.High, Bit.Low, Bit.High, Bit.High)
+            bits['E'] = listOf(Bit.Low, Bit.Low, Bit.High, Bit.High, Bit.High)
+            bits['F'] = listOf(Bit.Low, Bit.High, Bit.High, Bit.High, Bit.High)
+        }
+
     }
 
-    init {
-        val bits = mutableMapOf<Char, List<Bit>>()
-        /* bitfield: clock, bits 2^1, 2^2, 2^3, 2^4 */
-        bits['0'] = listOf(Bit.Low, Bit.Low, Bit.Low, Bit.Low, Bit.Low)
-        bits['1'] = listOf(Bit.Low, Bit.High, Bit.Low, Bit.Low, Bit.Low)
-        bits['2'] = listOf(Bit.Low, Bit.Low, Bit.High, Bit.Low, Bit.Low)
-        bits['3'] = listOf(Bit.Low, Bit.High, Bit.High, Bit.Low, Bit.Low)
-        bits['4'] = listOf(Bit.Low, Bit.Low, Bit.Low, Bit.High, Bit.Low)
-        bits['5'] = listOf(Bit.Low, Bit.High, Bit.Low, Bit.High, Bit.Low)
-        bits['6'] = listOf(Bit.Low, Bit.Low, Bit.High, Bit.High, Bit.Low)
-        bits['7'] = listOf(Bit.Low, Bit.High, Bit.High, Bit.High, Bit.Low)
-        bits['8'] = listOf(Bit.Low, Bit.Low, Bit.Low, Bit.Low, Bit.High)
-        bits['9'] = listOf(Bit.Low, Bit.High, Bit.Low, Bit.Low, Bit.High)
-        bits['A'] = listOf(Bit.Low, Bit.Low, Bit.High, Bit.Low, Bit.High)
-        bits['B'] = listOf(Bit.Low, Bit.High, Bit.High, Bit.Low, Bit.High)
-        bits['C'] = listOf(Bit.Low, Bit.Low, Bit.Low, Bit.High, Bit.High)
-        bits['D'] = listOf(Bit.Low, Bit.High, Bit.Low, Bit.High, Bit.High)
-        bits['E'] = listOf(Bit.Low, Bit.Low, Bit.High, Bit.High, Bit.High)
-        bits['F'] = listOf(Bit.Low, Bit.High, Bit.High, Bit.High, Bit.High)
+
+    open fun calculateSteps(flickerCode: String): List<Array<Bit>> {
+
+        val halfbyteid = ObjectHolder(0)
+        val clock = ObjectHolder(Bit.High)
+        val bitarray = mutableListOf<MutableList<Bit>>()
+
 
         /* prepend synchronization identifier */
-        code = "0FFF" + code
+        var code = "0FFF" + flickerCode
         if (code.length % 2 != 0) {
             code += "F"
         }
@@ -49,24 +53,24 @@ open class FlickerCodeStepsCalculator(var code: String) {
         val steps = mutableListOf<Array<Bit>>()
 
         do {
-            steps.add(step())
-        } while (halfbyteid > 0 || clock == Bit.Low)
+            steps.add(calculateStep(halfbyteid, clock, bitarray))
+        } while (halfbyteid.value > 0 || clock.value == Bit.Low)
 
-        this.steps = steps
+        return steps
     }
 
-    fun step(): Array<Bit> {
-        bitarray[halfbyteid][0] = clock
+    protected open fun calculateStep(halfbyteid: ObjectHolder<Int>, clock: ObjectHolder<Bit>, bitarray: MutableList<MutableList<Bit>>): Array<Bit> {
+        bitarray[halfbyteid.value][0] = clock.value
 
-        val stepBits = Array(5) { index -> bitarray[halfbyteid][index] }
+        val stepBits = Array(5) { index -> bitarray[halfbyteid.value][index] }
 
-        clock = clock.invert()
+        clock.value = clock.value.invert()
 
-        if (clock == Bit.High) {
-            halfbyteid++
+        if (clock.value == Bit.High) {
+            halfbyteid.value++
 
-            if (halfbyteid >= bitarray.size) {
-                halfbyteid = 0
+            if (halfbyteid.value >= bitarray.size) {
+                halfbyteid.value = 0
             }
 
         }
diff --git a/ui/BankingUiCommon/src/commonMain/kotlin/net/dankito/banking/ui/util/FlickerCodeAnimator.kt b/ui/BankingUiCommon/src/commonMain/kotlin/net/dankito/banking/ui/util/FlickerCodeAnimator.kt
index 987d7c81..9a3fceb5 100644
--- a/ui/BankingUiCommon/src/commonMain/kotlin/net/dankito/banking/ui/util/FlickerCodeAnimator.kt
+++ b/ui/BankingUiCommon/src/commonMain/kotlin/net/dankito/banking/ui/util/FlickerCodeAnimator.kt
@@ -39,7 +39,7 @@ open class FlickerCodeAnimator {
         currentFrequency = frequency
 
         animationJob = GlobalScope.launch(Dispatchers.Default) {
-            val steps = FlickerCodeStepsCalculator(flickerCode.parsedDataSet).steps
+            val steps = FlickerCodeStepsCalculator().calculateSteps(flickerCode.parsedDataSet)
 
             calculateAnimation(steps, showStep)
         }