introduce Icepick.

app/build.gradle

@@ -72,6 +72,7 @@ repositories {
   maven { url 'https://github.com/lijingle1/stetho-realm/raw/master/maven-repo' }
   maven { url 'https://github.com/RocketChat/Android-DDP/raw/master/repository' }
   maven { url 'http://dl.bintray.com/amulyakhare/maven' }
+  maven {url "https://clojars.org/repo/"} //for icepick.
 }
 
 dependencies {
@@ -97,4 +98,7 @@ dependencies {
   compile 'com.trello:rxlifecycle-components:1.0'
 
   compile 'com.amulyakhare:com.amulyakhare.textdrawable:1.0.1'
+
+  compile 'frankiesardo:icepick:3.2.0'
+  provided 'frankiesardo:icepick-processor:3.2.0'
 }

app/proguard-rules.pro

@@ -15,3 +15,13 @@
 #-keepclassmembers class fqcn.of.javascript.interface.for.webview {
 #   public *;
 #}
+
+
+# Icepick
+-dontwarn icepick.**
+-keep class icepick.** { *; }
+-keep class **$$Icepick { *; }
+-keepclasseswithmembernames class * {
+    @icepick.* <fields>;
+}
+-keepnames class * { @icepick.State *;}
\ No newline at end of file

app/src/main/java/chat/rocket/android/activity/AbstractFragmentActivity.java

 package chat.rocket.android.activity;
 
+import android.os.Bundle;
 import android.support.annotation.IdRes;
+import android.support.annotation.Nullable;
 import android.support.v4.app.Fragment;
 import android.support.v4.app.FragmentManager;
 import chat.rocket.android.helper.OnBackPressListener;
 import com.trello.rxlifecycle.components.support.RxAppCompatActivity;
+import icepick.Icepick;
 
 abstract class AbstractFragmentActivity extends RxAppCompatActivity {
 
+  @Override protected void onCreate(@Nullable Bundle savedInstanceState) {
+    super.onCreate(savedInstanceState);
+    Icepick.restoreInstanceState(this, savedInstanceState);
+  }
+
+  @Override protected void onSaveInstanceState(Bundle outState) {
+    super.onSaveInstanceState(outState);
+    Icepick.saveInstanceState(this, outState);
+  }
+
   protected abstract @IdRes int getLayoutContainerForFragment();
 
   @Override public final void onBackPressed() {