Navigation : add simple fragment backstack management.

app/src/main/java/im/vector/riotredesign/core/platform/OnBackPressed.kt

@@ -0,0 +1,10 @@
+package im.vector.riotredesign.core.platform
+
+interface OnBackPressed {
+
+    /**
+     * Returns true, if the on back pressed event has been handled by this Fragment.
+     * Otherwise return false
+     */
+    fun onBackPressed(): Boolean
+}

app/src/main/java/im/vector/riotredesign/core/platform/RiotFragment.kt

@@ -2,12 +2,15 @@ package im.vector.riotredesign.core.platform
 
 import com.airbnb.mvrx.BaseMvRxFragment
 
-abstract class RiotFragment : BaseMvRxFragment() {
+abstract class RiotFragment : BaseMvRxFragment(), OnBackPressed {
 
     val riotActivity: RiotActivity by lazy {
         activity as RiotActivity
     }
 
+    override fun onBackPressed(): Boolean {
+        return false
+    }
 
     override fun invalidate() {
         //no-ops by default

app/src/main/java/im/vector/riotredesign/features/MainActivity.kt

@@ -5,14 +5,12 @@ import im.vector.matrix.android.api.Matrix
 import im.vector.riotredesign.core.platform.RiotActivity
 import im.vector.riotredesign.features.home.HomeActivity
 import im.vector.riotredesign.features.login.LoginActivity
-import org.koin.android.ext.android.inject
 
 
 class MainActivity : RiotActivity() {
 
     private val authenticator = Matrix.getInstance().authenticator()
 
-
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         val intent = if (authenticator.hasActiveSessions()) {

app/src/main/java/im/vector/riotredesign/features/RootFlowCoordinator.kt

@@ -1,4 +0,0 @@
-package im.vector.riotredesign.features
-
-class RootFlowCoordinator {
-}

app/src/main/java/im/vector/riotredesign/features/home/HomeActivity.kt

@@ -3,6 +3,7 @@ package im.vector.riotredesign.features.home
 import android.content.Context
 import android.content.Intent
 import android.os.Bundle
+import android.support.v4.app.FragmentManager
 import android.support.v4.view.GravityCompat
 import android.support.v4.widget.DrawerLayout
 import android.support.v7.app.ActionBarDrawerToggle
@@ -12,6 +13,7 @@ import android.view.MenuItem
 import android.view.View
 import im.vector.riotredesign.R
 import im.vector.riotredesign.core.extensions.replaceFragment
+import im.vector.riotredesign.core.platform.OnBackPressed
 import im.vector.riotredesign.core.platform.RiotActivity
 import im.vector.riotredesign.core.platform.ToolbarConfigurable
 import im.vector.riotredesign.features.home.room.detail.LoadingRoomDetailFragment
@@ -46,7 +48,6 @@ class HomeActivity : RiotActivity(), HomeNavigator, ToolbarConfigurable {
 
     override fun onOptionsItemSelected(item: MenuItem): Boolean {
         when (item.itemId) {
-            // Android home
             android.R.id.home -> {
                 drawerLayout.openDrawer(GravityCompat.START)
                 return true
@@ -60,10 +61,30 @@ class HomeActivity : RiotActivity(), HomeNavigator, ToolbarConfigurable {
         if (drawerLayout.isDrawerOpen(Gravity.LEFT)) {
             drawerLayout.closeDrawer(Gravity.LEFT)
         } else {
-            super.onBackPressed()
+            val handled = recursivelyDispatchOnBackPressed(supportFragmentManager)
+            if (!handled) {
+                super.onBackPressed()
+            }
         }
     }
 
+    private fun recursivelyDispatchOnBackPressed(fm: FragmentManager): Boolean {
+        if (fm.backStackEntryCount == 0)
+            return false
+        val reverseOrder = fm.fragments.filter { it is OnBackPressed }.reversed()
+        for (f in reverseOrder) {
+            val handledByChildFragments = recursivelyDispatchOnBackPressed(f.childFragmentManager)
+            if (handledByChildFragments) {
+                return true
+            }
+            val backPressable = f as OnBackPressed
+            if (backPressable.onBackPressed()) {
+                return true
+            }
+        }
+        return false
+    }
+
     // HomeNavigator *******************************************************************************
 
     override fun openRoomDetail(roomId: String, eventId: String?) {

app/src/main/java/im/vector/riotredesign/features/home/HomeFlowCoordinator.kt

@@ -1,4 +0,0 @@
-package im.vector.riotredesign.features.home
-
-class HomeFlowCoordinator {
-}

app/src/main/java/im/vector/riotredesign/features/login/LoginFlowCoordinator.kt

@@ -1,2 +0,0 @@
-package im.vector.riotredesign.features.login
-