fade out enabled for set minutes and added volumen bar in ui

app/src/main/java/com/example/hairdryer/MainActivity.kt

@@ -7,7 +7,9 @@ import android.media.SoundPool
 import android.os.Bundle
 import android.os.Handler
 import android.widget.EditText
+import android.widget.ProgressBar
 import android.widget.TextView
+import kotlin.math.pow
 
 class MainActivity : Activity() {
 
@@ -18,6 +20,9 @@ class MainActivity : Activity() {
     private var isPlaying = false
     private var remainingMinutes = 0
     private var countdownRunnable: Runnable? = null
+    private var fadeRunnable: Runnable? = null
+    private var totalMillis: Long = 0
+    private var startTime: Long = 0
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
@@ -25,6 +30,7 @@ class MainActivity : Activity() {
 
         val status = findViewById<TextView>(R.id.statusText)
         val input = findViewById<EditText>(R.id.timerInput)
+        val volumeBar = findViewById<ProgressBar>(R.id.volumeBar)
 
         val attrs = AudioAttributes.Builder()
             .setUsage(AudioAttributes.USAGE_MEDIA)
@@ -38,59 +44,92 @@ class MainActivity : Activity() {
 
         soundId = soundPool.load(this, R.raw.sound, 1)
 
-        // Anfangszustand
-        updateUI(status, "Ready", Color.LTGRAY)
+        updateUI(status, volumeBar, "Ready", Color.LTGRAY, 1f)
 
-        // Das Statusfeld ist jetzt klickbar
         status.setOnClickListener {
             if (isPlaying) {
-                stopSound(status)
+                stopSound(status, volumeBar)
             } else {
                 val min = input.text.toString().toIntOrNull() ?: 0
-                startSound(min, status)
+                startSound(min, status, volumeBar)
             }
         }
     }
 
-    private fun startSound(minutes: Int, status: TextView) {
-        stopSound(status)
+    private fun startSound(minutes: Int, status: TextView, volumeBar: ProgressBar) {
+        stopSound(status, volumeBar)
         streamId = soundPool.play(soundId, 1f, 1f, 1, -1, 1f)
         isPlaying = true
+        startTime = System.currentTimeMillis()
 
         if (minutes > 0) {
             remainingMinutes = minutes
-            updateUI(status, "Runs for: $remainingMinutes min", Color.GREEN)
+            totalMillis = minutes * 60_000L
+            updateUI(status, volumeBar, "Runs for: $remainingMinutes min", Color.GREEN, 1f)
+
+            // Countdown jede Minute
             countdownRunnable = object : Runnable {
                 override fun run() {
                     remainingMinutes--
                     if (remainingMinutes > 0) {
-                        updateUI(status, "Runs for: $remainingMinutes min", Color.GREEN)
+                        updateUI(status, volumeBar, "Runs for: $remainingMinutes min", Color.GREEN, currentVolume())
                         handler.postDelayed(this, 60_000L)
                     } else {
-                        stopSound(status)
+                        stopSound(status, volumeBar)
                     }
                 }
             }
             handler.postDelayed(countdownRunnable!!, 60_000L)
+
+            // Exponentieller Fade-Out alle 200 ms
+            fadeRunnable = object : Runnable {
+                override fun run() {
+                    if (!isPlaying) return
+                    val elapsed = System.currentTimeMillis() - startTime
+                    val progress = (elapsed.toFloat() / totalMillis).coerceIn(0f, 1f)
+                    // exponentielles Absenken: volume = (1 - progress)^2
+                    val volume = (1 - progress).pow(2)
+                    soundPool.setVolume(streamId, volume, volume)
+                    volumeBar.progress = (volume * 100).toInt()
+                    if (progress < 1f) {
+                        handler.postDelayed(this, 200L)
                     } else {
-            updateUI(status, "Runs: ∞", Color.GREEN)
+                        stopSound(status, volumeBar)
+                    }
+                }
+            }
+            handler.postDelayed(fadeRunnable!!, 200L)
+
+        } else {
+            // unendlich
+            updateUI(status, volumeBar, "Runs: ∞", Color.GREEN, 1f)
+            volumeBar.progress = 100
         }
     }
 
-    private fun stopSound(status: TextView) {
+    private fun stopSound(status: TextView, volumeBar: ProgressBar) {
         if (isPlaying) {
             soundPool.stop(streamId)
             isPlaying = false
         }
         remainingMinutes = 0
         handler.removeCallbacks(countdownRunnable ?: Runnable { })
-        updateUI(status, "Stopped", Color.RED)
+        handler.removeCallbacks(fadeRunnable ?: Runnable { })
+        updateUI(status, volumeBar, "Stopped", Color.RED, 0f)
+        volumeBar.progress = 0
     }
 
-    private fun updateUI(view: TextView, text: String, color: Int) {
+    private fun updateUI(view: TextView, bar: ProgressBar, text: String, color: Int, volume: Float) {
         view.text = text
         view.setBackgroundColor(color)
         view.setTextColor(Color.BLACK)
+        bar.progress = (volume * 100).toInt()
+    }
+
+    private fun currentVolume(): Float {
+        val elapsed = System.currentTimeMillis() - startTime
+        val progress = (elapsed.toFloat() / totalMillis).coerceIn(0f, 1f)
+        return (1 - progress).pow(2)
     }
 
     override fun onDestroy() {

app/src/main/res/layout/activity_main.xml

@@ -37,4 +37,13 @@
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:layout_marginTop="20dp"/>
+
+    <ProgressBar
+        android:id="@+id/volumeBar"
+        style="@android:style/Widget.ProgressBar.Horizontal"
+        android:layout_width="match_parent"
+        android:layout_height="24dp"
+        android:layout_marginTop="20dp"
+        android:max="100"
+        android:progress="100"/>
 </LinearLayout>