diff --git a/README.md b/README.md
index 2e49f65..c134713 100644
--- a/README.md
+++ b/README.md
@@ -9,19 +9,19 @@ The Mqtt Android Service is an MQTT client library for developing applications o
 **Step 1.** Add it in your root **build.gradle** at the end of repositories:
 
 ```groovy
-	allprojects {
-		repositories {
-			...
-			maven { url 'https://jitpack.io' }
-		}
-	}
+allprojects {
+    repositories {
+        ...
+        maven { url 'https://jitpack.io' }
+    }
+}
 ```
 
 **Step 2.** Add the dependency:
 
 ```groovy
 dependencies {
-	        implementation 'com.github.shiyinghan:MqttAndroid:1.0.0'
-	}
+    implementation 'com.github.shiyinghan:MqttAndroid:1.0.0'
+}
 ```
 
diff --git a/app/src/main/AndroidManifest.xml b/app/src/main/AndroidManifest.xml
index 8bc81fb..2ce5515 100644
--- a/app/src/main/AndroidManifest.xml
+++ b/app/src/main/AndroidManifest.xml
@@ -22,7 +22,8 @@
 
         <activity
             android:name=".module.activity.ConnectionListActivity"
-            android:launchMode="singleTask">
+            android:launchMode="singleTask"
+            android:screenOrientation="portrait">
             <intent-filter>
                 <action android:name="android.intent.action.MAIN" />
 
@@ -31,9 +32,11 @@
         </activity>
         <activity
             android:name=".module.activity.ConnectionEditActivity"
+            android:screenOrientation="portrait"
             android:windowSoftInputMode="stateHidden|adjustResize" />
         <activity
             android:name=".module.activity.ConnectionPortalActivity"
+            android:screenOrientation="portrait"
             android:windowSoftInputMode="stateHidden|adjustResize" />
     </application>
 
diff --git a/mqtt/src/main/java/com/shiyinghan/mqtt/android/service/MqttAndroidClient.java b/mqtt/src/main/java/com/shiyinghan/mqtt/android/service/MqttAndroidClient.java
index 2708cd9..9a2b2f4 100644
--- a/mqtt/src/main/java/com/shiyinghan/mqtt/android/service/MqttAndroidClient.java
+++ b/mqtt/src/main/java/com/shiyinghan/mqtt/android/service/MqttAndroidClient.java
@@ -1649,7 +1649,7 @@ public void onFailure(IMqttToken asyncActionToken, Throwable exception) {
     synchronized void notifyOffline() {
         traceDebug(TAG, "Offline with client:" + getClientId() + '/' + getServerURI());
 
-        if (callback != null && !connectOptions.isCleanSession()) {
+        if (isConnected() && callback != null && !connectOptions.isCleanSession()) {
             Exception e = new Exception("Android offline");
             callback.connectionLost(e);
         }