title: Unresolved Class .MainActivity in Activity.xml file
body: <p>I have been following some Course and suddenly I have got this error.Don't know what happened, searched on google but couldn't find the valuable answer. I have also tried invalid cached and restart but nothing happen.</p>
  
  <p>Here is my Android Manifest file</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;manifest xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:tools="http://schemas.android.com/tools"
  package="com.example.shoaib.miwokapp"&gt;
  
  &lt;application
      android:allowBackup="true"
      android:icon="@mipmap/ic_launcher"
      android:label="@string/app_name"
      android:roundIcon="@mipmap/ic_launcher_round"
      android:supportsRtl="true"
      android:theme="@style/AppTheme"
      tools:ignore="GoogleAppIndexingWarning"&gt;
      &lt;activity android:name=".MainActivity"&gt;
          &lt;intent-filter&gt;
              &lt;action android:name="android.intent.action.MAIN" /&gt;
  
              &lt;category android:name="android.intent.category.LAUNCHER" /&gt;
          &lt;/intent-filter&gt;
      &lt;/activity&gt;
      &lt;activity
          android:name=".NmbersActivity"
          android:label="Numbers Activity" /&gt;
      &lt;activity
          android:name=".MembersActivity"
          android:label="Members Activity" /&gt;
      &lt;activity
          android:name=".PhrasesActivity"
          android:label="Phrases Activity" /&gt;
      &lt;activity
          android:name=".ColorActivity"
          android:label="Color Activity" /&gt;
  
  
   &lt;/application&gt;
  
  &lt;/manifest&gt;
  </code></pre>
  
  <p>Here is the activity_main.xml file with the error</p>
  
  <pre><code> &lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;LinearLayout
   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:layout_width="match_parent"
   android:background="#FFF7DA"
   android:orientation="vertical"
   android:layout_height="match_parent"
   tools:context="com.example.shoaib.miwokapp.MainActivity"&gt;
  
  &lt;TextView
      style="@style/CategoryStyle"
      android:id="@+id/clickNumber"
      android:layout_width="match_parent"
      android:layout_height="88dp"
      android:padding="12dp"
      android:background="#FD8E09"
      android:textColor="#FFFFFF"
      android:paddingLeft="16dp"
      android:paddingStart="16dp"
      android:textStyle="bold"
      android:text="@string/numbers"
      android:textSize="18sp" /&gt;
  
  
  &lt;TextView
      style="@style/CategoryStyle"
      android:id="@+id/clickMembers"
      android:layout_width="match_parent"
      android:layout_height="88dp"
      android:text="@string/family_members"
      android:textSize="18sp"
      android:background="#379237"
      android:padding="12dp"
      android:textColor="#FFFFFF"
      android:textStyle="bold"
      android:paddingLeft="16dp"
      android:paddingStart="16dp" /&gt;
  
  
  &lt;TextView
      style="@style/CategoryStyle"
      android:id="@+id/clickColor"
      android:layout_width="match_parent"
      android:layout_height="88dp"
      android:text="@string/colors"
      android:textSize="18sp"
      android:textColor="#FFFFFF"
      android:background="#8800A0"
      android:padding="12dp"
      android:textStyle="bold"
      android:paddingLeft="16dp"
      android:paddingStart="16dp" /&gt;
  
  &lt;TextView
      style="@style/CategoryStyle"
      android:id="@+id/clickPhrases"
      android:layout_width="match_parent"
      android:layout_height="88dp"
      android:text="@string/phrases"
      android:background="#16AFCA"
      android:textSize="18sp"
      android:textColor="#FFFFFF"
      android:textStyle="bold"
      android:padding="12dp"
      android:paddingLeft="16dp"
      android:paddingStart="16dp" /&gt;
  
  &lt;/LinearLayout&gt;
  </code></pre>
  
  <p>My build.gradle file</p>
  
  <pre><code>android {
     compileSdkVersion 28
     defaultConfig {
          applicationId "com.example.shoaib.miwokapp"
          minSdkVersion 16
          targetSdkVersion 28
          versionCode 1
          versionName "1.0"
          testInstrumentationRunner 
  "android.support.test.runner.AndroidJUnitRunner"
  }
  buildTypes {
      release {
          minifyEnabled false
          proguardFiles getDefaultProguardFile('proguard-android.txt'), 
  'proguard-rules.pro'
      }
  }
  sourceSets { main { assets.srcDirs = ['src/main/asserts', 
  'src/main/assets/'] } }
  }
  
  dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:28.0.0'
    implementation 'com.android.support.constraint:constraint-layout:1.1.3'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso- 
   core:3.0.2'
   }
  </code></pre>
  
  <p>Thank you</p>