diff --git a/app/src/main/java/cc/niushuai/project/devcontrol/MainActivity.java b/app/src/main/java/cc/niushuai/project/devcontrol/MainActivity.java
index 24af5fb..96f0e93 100644
--- a/app/src/main/java/cc/niushuai/project/devcontrol/MainActivity.java
+++ b/app/src/main/java/cc/niushuai/project/devcontrol/MainActivity.java
@@ -54,6 +54,7 @@ public class MainActivity extends AppCompatActivity {
 //                // 设置页签
 //                R.id.id_bottom_nav_menu_set
 //        ).build();
+        // 返回键 左上角以及右上角
 //        NavigationUI.setupActionBarWithNavController(this, navController, appBarConfiguration);
 
         // 底部导航栏
diff --git a/app/src/main/res/layout/activity_main.xml b/app/src/main/res/layout/activity_main.xml
index 6b6968d..354b7cc 100644
--- a/app/src/main/res/layout/activity_main.xml
+++ b/app/src/main/res/layout/activity_main.xml
@@ -1,6 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
     android:id="@+id/id_am_container"
     android:layout_width="match_parent"
     android:layout_height="match_parent"