Use ?.let instead if-null-test, avoid runnable

app/src/main/kotlin/de/rochefort/childmonitor/DiscoverActivity.kt

@@ -91,10 +91,10 @@ class DiscoverActivity : Activity() {
 
     override fun onDestroy() {
         Log.i(TAG, "ChildMonitoring stop")
-        if (this.discoveryListener != null) {
+        this.discoveryListener?.let {
-            Log.i(TAG, "Unregistering monitoring service")
-            this.nsdManager!!.stopServiceDiscovery(discoveryListener)
             this.discoveryListener = null
+            Log.i(TAG, "Unregistering monitoring service")
+            this.nsdManager!!.stopServiceDiscovery(it)
         }
         super.onDestroy()
     }
@@ -102,17 +102,14 @@ class DiscoverActivity : Activity() {
     private fun startServiceDiscovery(serviceType: String) {
         val nsdManager = this.getSystemService(NSD_SERVICE) as NsdManager
         val wifi = this.applicationContext.getSystemService(WIFI_SERVICE) as WifiManager
-        val multicastReleaser: Runnable
+        val multicastLock = wifi.createMulticastLock("multicastLock")
-        multicastReleaser = run {
+        multicastLock.setReferenceCounted(true)
-            val multicastLock = wifi.createMulticastLock("multicastLock")
+        multicastLock.acquire()
-            multicastLock.setReferenceCounted(true)
+        val multicastReleaser = {
-            multicastLock.acquire()
+            try {
-            Runnable {
+                multicastLock.release()
-                try {
+            } catch (ignored: Exception) {
-                    multicastLock.release()
+                // don't really care
-                } catch (ignored: Exception) {
-                    //dont really care
-                }
             }
         }
         val serviceTable = findViewById<ListView>(R.id.ServiceTable)
@@ -121,9 +118,8 @@ class DiscoverActivity : Activity() {
         serviceTable.adapter = availableServicesAdapter
         serviceTable.onItemClickListener = OnItemClickListener { parent: AdapterView<*>, _: View?, position: Int, _: Long ->
             val info = parent.getItemAtPosition(position) as ServiceInfoWrapper
-            val address = info.address
+            info.address?.let {
-            if (address != null) {
+                connectToChild(it, info.port, info.name)
-                connectToChild(address, info.port, info.name)
             }
         }
 
@@ -172,24 +168,24 @@ class DiscoverActivity : Activity() {
                 // When the network service is no longer available.
                 // Internal bookkeeping code goes here.
                 Log.e(TAG, "Service lost: $service")
-                multicastReleaser.run()
+                multicastReleaser()
             }
 
             override fun onDiscoveryStopped(serviceType: String) {
                 Log.i(TAG, "Discovery stopped: $serviceType")
-                multicastReleaser.run()
+                multicastReleaser()
             }
 
             override fun onStartDiscoveryFailed(serviceType: String, errorCode: Int) {
                 Log.e(TAG, "Discovery failed: Error code: $errorCode")
                 nsdManager.stopServiceDiscovery(this)
-                multicastReleaser.run()
+                multicastReleaser()
             }
 
             override fun onStopDiscoveryFailed(serviceType: String, errorCode: Int) {
                 Log.e(TAG, "Discovery failed: Error code: $errorCode")
                 nsdManager.stopServiceDiscovery(this)
-                multicastReleaser.run()
+                multicastReleaser()
             }
         }
         nsdManager.discoverServices(

app/src/main/kotlin/de/rochefort/childmonitor/ListenActivity.kt

@@ -65,10 +65,10 @@ class ListenActivity : Activity() {
     private fun ensureServiceRunningAndBind(bundle: Bundle?) {
         val context: Context = this
         val intent = Intent(context, ListenService::class.java)
-        if (bundle != null) {
+        bundle?.let {
-            intent.putExtra("name", bundle.getString("name"))
+            intent.putExtra("name", it.getString("name"))
-            intent.putExtra("address", bundle.getString("address"))
+            intent.putExtra("address", it.getString("address"))
-            intent.putExtra("port", bundle.getInt("port"))
+            intent.putExtra("port", it.getInt("port"))
             ContextCompat.startForegroundService(context, intent)
         }
         // Attempts to establish a connection with the service.  We use an

app/src/main/kotlin/de/rochefort/childmonitor/ListenService.kt

@@ -58,25 +58,23 @@ class ListenService : Service() {
         Log.i(TAG, "Received start id $startId: $intent")
         // Display a notification about us starting.  We put an icon in the status bar.
         createNotificationChannel()
-        val extras = intent.extras
+        intent.extras?.let {
-        if (extras != null) {
+            val name = it.getString("name")
-            val name = extras.getString("name")
             childDeviceName = name
             val n = buildNotification(name)
             val foregroundServiceType = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) ServiceInfo.FOREGROUND_SERVICE_TYPE_MEDIA_PLAYBACK else 0 // Keep the linter happy
             ServiceCompat.startForeground(this, ID, n, foregroundServiceType)
-            val address = extras.getString("address")
+            val address = it.getString("address")
-            val port = extras.getInt("port")
+            val port = it.getInt("port")
             doListen(address, port)
         }
         return START_REDELIVER_INTENT
     }
 
     override fun onDestroy() {
-        val lt = this.listenThread
+        this.listenThread?.let {
-        if (lt != null) {
-            lt.interrupt()
             this.listenThread = null
+            it.interrupt()
         }
 
         // Cancel the persistent notification.
@@ -121,12 +119,12 @@ class ListenService : Service() {
         }
     }
 
-    fun setErrorCallback(errorCallback: Runnable?) {
+    fun setErrorCallback(errorCallback: (() -> Unit)) {
-        mErrorCallback = errorCallback
+        this.errorCallback = errorCallback
     }
 
-    fun setUpdateCallback(updateCallback: Runnable?) {
+    fun setUpdateCallback(updateCallback: (() -> Unit)) {
-        mUpdateCallback = updateCallback
+        this.updateCallback = updateCallback
     }
 
     inner class ListenBinder : Binder() {
@@ -134,8 +132,8 @@ class ListenService : Service() {
             get() = this@ListenService
     }
 
-    private var mErrorCallback: Runnable? = null
+    private var errorCallback: (() -> Unit)? = null
-    private var mUpdateCallback: Runnable? = null
+    private var updateCallback: (() -> Unit)? = null
     private fun doListen(address: String?, port: Int) {
         val lt = Thread {
             try {
@@ -150,8 +148,7 @@ class ListenService : Service() {
                 // an alert to notify the user that the connection has been
                 // interrupted.
                 playAlert()
-                val errorCallback = mErrorCallback
+                errorCallback?.invoke()
-                errorCallback?.run()
             }
         }
         this.listenThread = lt
@@ -181,8 +178,7 @@ class ListenService : Service() {
                     val decodedBytes = ShortArray(decoded)
                     System.arraycopy(decodedBuffer, 0, decodedBytes, 0, decoded)
                     volumeHistory.onAudioData(decodedBytes)
-                    val updateCallback = mUpdateCallback
+                    updateCallback?.invoke()
-                    updateCallback?.run()
                 }
             }
         } catch (e: Exception) {

app/src/main/kotlin/de/rochefort/childmonitor/MonitorActivity.kt

@@ -120,9 +120,9 @@ class MonitorActivity : Activity() {
 
     private fun doUnbindAndStopService() {
         if (this.shouldUnbind) {
+            this.shouldUnbind = false
             // Release information about the service's state.
             unbindService(connection)
-            this.shouldUnbind = false
         }
         val context: Context = this
         val intent = Intent(context, MonitorService::class.java)

app/src/main/kotlin/de/rochefort/childmonitor/MonitorService.kt

@@ -200,11 +200,10 @@ class MonitorService : Service() {
     }
 
     private fun unregisterService() {
-        val currentListener = this.registrationListener
+        this.registrationListener?.let {
-        if (currentListener != null) {
-            Log.i(TAG, "Unregistering monitoring service")
-            this.nsdManager!!.unregisterService(currentListener)
             this.registrationListener = null
+            Log.i(TAG, "Unregistering monitoring service")
+            this.nsdManager!!.unregisterService(it)
         }
     }
 
@@ -231,18 +230,16 @@ class MonitorService : Service() {
     }
 
     override fun onDestroy() {
-        val mt = this.monitorThread
+        this.monitorThread?.let {
-        if (mt != null) {
-            mt.interrupt()
             this.monitorThread = null
+            it.interrupt()
         }
         unregisterService()
         this.connectionToken = null
-        val sock = this.currentSocket
+        this.currentSocket?.let {
-        if (sock != null) {
+            this.currentSocket = null
             try {
-                sock.close()
+                it.close()
-                this.currentSocket = null
             } catch (e: IOException) {
                 Log.e(TAG, "Failed to close active socket on port $currentPort")
             }