implement setUsername and joinDefaultChannels and so on ...

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

@@ -5,6 +5,7 @@ import android.os.Bundle;
 import chat.rocket.android.LaunchUtil;
 import chat.rocket.android.RocketChatCache;
 import chat.rocket.android.model.ServerConfig;
+import chat.rocket.android.model.ddp.RoomSubscription;
 import chat.rocket.android.realm_helper.RealmListObserver;
 import chat.rocket.android.realm_helper.RealmStore;
 import chat.rocket.android.service.RocketChatService;
@@ -36,16 +37,28 @@ abstract class AbstractAuthedActivity extends AbstractFragmentActivity {
   private void updateServerConfigIdIfNeeded(SharedPreferences prefs) {
     String newServerConfigId = prefs.getString(RocketChatCache.KEY_SELECTED_SERVER_CONFIG_ID, null);
     if (serverConfigId == null) {
-      if (newServerConfigId != null) {
+      if (newServerConfigId != null && assertServerConfigExists(newServerConfigId, prefs)) {
         updateServerConfigId(newServerConfigId);
       }
     } else {
-      if (!serverConfigId.equals(newServerConfigId)) {
+      if (!serverConfigId.equals(newServerConfigId)
+          && assertServerConfigExists(newServerConfigId, prefs)) {
         updateServerConfigId(newServerConfigId);
       }
     }
   }
 
+  private boolean assertServerConfigExists(String serverConfigId, SharedPreferences prefs) {
+    if (RealmStore.get(serverConfigId) == null) {
+      prefs.edit()
+          .remove(RocketChatCache.KEY_SELECTED_SERVER_CONFIG_ID)
+          .remove(RocketChatCache.KEY_SELECTED_ROOM_ID)
+          .apply();
+      return false;
+    }
+    return true;
+  }
+
   private void updateServerConfigId(String serverConfigId) {
     this.serverConfigId = serverConfigId;
     onServerConfigIdUpdated();
@@ -54,16 +67,32 @@ abstract class AbstractAuthedActivity extends AbstractFragmentActivity {
   private void updateRoomIdIfNeeded(SharedPreferences prefs) {
     String newRoomId = prefs.getString(RocketChatCache.KEY_SELECTED_ROOM_ID, null);
     if (roomId == null) {
-      if (newRoomId != null) {
+      if (newRoomId != null && assertRoomSubscriptionExists(newRoomId, prefs)) {
         updateRoomId(newRoomId);
       }
     } else {
-      if (!roomId.equals(newRoomId)) {
+      if (!roomId.equals(newRoomId) && assertRoomSubscriptionExists(newRoomId, prefs)) {
         updateRoomId(newRoomId);
       }
     }
   }
 
+  private boolean assertRoomSubscriptionExists(String roomId, SharedPreferences prefs) {
+    if (!assertServerConfigExists(serverConfigId, prefs)) {
+      return false;
+    }
+
+    RoomSubscription room = RealmStore.get(serverConfigId).executeTransactionForRead(realm ->
+        realm.where(RoomSubscription.class).equalTo("rid", roomId).findFirst());
+    if (room == null) {
+      prefs.edit()
+          .remove(RocketChatCache.KEY_SELECTED_ROOM_ID)
+          .apply();
+      return false;
+    }
+    return true;
+  }
+
   private void updateRoomId(String roomId) {
     this.roomId = roomId;
     onRoomIdUpdated();

app/src/main/java/chat/rocket/android/api/MethodCallHelper.java

@@ -119,6 +119,18 @@ public class MethodCallHelper {
         ));
   }
 
+  /**
+   * set current user's name.
+   */
+  public Task<String> setUsername(final String username) {
+    return call("setUsername", TIMEOUT_MS, () -> new JSONArray().put(username));
+  }
+
+  public Task<Void> joinDefaultChannels() {
+    return call("joinDefaultChannels", TIMEOUT_MS)
+        .onSuccessTask(task -> Task.forResult(null));
+  }
+
   /**
    * Login with username/email and password.
    */

app/src/main/java/chat/rocket/android/fragment/server_config/UserRegistrationDialogFragment.java

@@ -112,6 +112,8 @@ public class UserRegistrationDialogFragment extends DialogFragment {
       MethodCallHelper methodCallHelper = new MethodCallHelper(serverConfigId);
       methodCallHelper.registerUser(username, email, password, password)
           .onSuccessTask(task -> methodCallHelper.loginWithEmail(email, password))
+          .onSuccessTask(task -> methodCallHelper.setUsername(username)) //TODO: should prompt!
+          .onSuccessTask(task -> methodCallHelper.joinDefaultChannels())
           .onSuccessTask(task -> {
             dismiss();
             return task;

app/src/main/java/chat/rocket/android/renderer/UserRenderer.java

@@ -5,6 +5,7 @@ import android.widget.ImageView;
 import android.widget.TextView;
 import chat.rocket.android.R;
 import chat.rocket.android.helper.Avatar;
+import chat.rocket.android.helper.TextUtils;
 import chat.rocket.android.model.ddp.User;
 
 /**
@@ -24,7 +25,9 @@ public class UserRenderer extends AbstractRenderer<User> {
       return this;
     }
 
-    new Avatar(hostname, object.getUsername()).into(imageView);
+    if (!TextUtils.isEmpty(object.getUsername())) {
+      new Avatar(hostname, object.getUsername()).into(imageView);
+    }
     return this;
   }