Fix problem with loss of result listener.

Issue #130

library/src/main/kotlin/com/github/terrakok/cicerone/BaseRouter.kt

@@ -10,12 +10,16 @@ abstract class BaseRouter {
     private val resultWire = ResultWire()
 
     /**
-     * Sets data listener with given key.
+     * Sets data listener with given key
+     * and returns [ResultListenerHandler] for availability to dispose subscription.
      *
      * After first call listener will be removed.
      */
-    fun setResultListener(key: String, listener: ResultListener) {
-        resultWire.setResultListener(key, listener)
+    fun setResultListener(
+        key: String,
+        listener: ResultListener
+    ): ResultListenerHandler {
+        return resultWire.setResultListener(key, listener)
     }
 
     /**
@@ -32,6 +36,5 @@ abstract class BaseRouter {
      */
     protected fun executeCommands(vararg commands: Command) {
         commandBuffer.executeCommands(commands)
-        resultWire.flush()
     }
 }

library/src/main/kotlin/com/github/terrakok/cicerone/ResultWire.kt

@@ -1,30 +1,30 @@
 package com.github.terrakok.cicerone
 
-import java.lang.ref.WeakReference
-
 /**
  * Interface definition for a result callback.
  */
 fun interface ResultListener {
     fun onResult(data: Any)
 }
 
-internal class ResultWire {
-    private val listeners = mutableMapOf<String, WeakReference<ResultListener>>()
+/**
+ * Handler for manual delete subscription and avoid leak
+ */
+fun interface ResultListenerHandler {
+    fun dispose()
+}
 
-    fun setResultListener(key: String, listener: ResultListener) {
-        listeners[key] = WeakReference(listener)
-    }
+internal class ResultWire {
+    private val listeners = mutableMapOf<String, ResultListener>()
 
-    fun sendResult(key: String, data: Any) {
-        listeners.remove(key)?.get()?.let { listener ->
-            listener.onResult(data)
+    fun setResultListener(key: String, listener: ResultListener): ResultListenerHandler {
+        listeners[key] = listener
+        return ResultListenerHandler {
+            listeners.remove(key)
         }
     }
 
-    fun flush() {
-        listeners.entries
-            .filter { it.value.get() == null }
-            .forEach { listeners.remove(it.key) }
+    fun sendResult(key: String, data: Any) {
+        listeners.remove(key)?.onResult(data)
     }
 }

sample/src/main/java/com/github/terrakok/cicerone/sample/mvp/animation/profile/ProfilePresenter.kt

@@ -1,5 +1,6 @@
 package com.github.terrakok.cicerone.sample.mvp.animation.profile
 
+import com.github.terrakok.cicerone.ResultListenerHandler
 import com.github.terrakok.cicerone.Router
 import com.github.terrakok.cicerone.sample.R
 import com.github.terrakok.cicerone.sample.Screens.SelectPhoto
@@ -13,6 +14,7 @@ import moxy.MvpPresenter
 class ProfilePresenter(
         private val router: Router
 ) : MvpPresenter<ProfileView>() {
+    private var resultListenerHandler: ResultListenerHandler? = null
 
     companion object {
         private const val RESULT_KEY = "photo_result"
@@ -25,12 +27,17 @@ class ProfilePresenter(
     }
 
     fun onPhotoClicked() {
-        router.setResultListener(RESULT_KEY) { data ->
+        resultListenerHandler = router.setResultListener(RESULT_KEY) { data ->
             viewState!!.showPhoto(data as Int)
         }
         router.navigateTo(SelectPhoto(RESULT_KEY))
     }
 
+    override fun onDestroy() {
+        resultListenerHandler?.dispose()
+        super.onDestroy()
+    }
+
     fun onBackPressed() {
         router.exit()
     }