title: Error in activity_main.xml after creating a new project
body: <p>I have created a new project and after build is done, when I tried opening activity_main.xml it is giving me following Rendering error:
  <a href="https://i.stack.imgur.com/Puq4U.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Puq4U.jpg" alt="Error in activity_main.xml"></a></p>
  
  <p>Can anyone tell, what's the possible reason behind this and how to solve this problem? I have just started learning android , but in the very beginning I am getting stuck. </p>
  
  <p>As asked, adding my app's build.gradle and layout.xml :</p>
  
  <p>Build.gradle:</p>
  
  <pre><code>apply plugin: 'com.android.application'
  
  android {
      compileSdkVersion 27
      buildToolsVersion "28.0.0"
      defaultConfig {
          applicationId "com.chanfool21.firstapp"
          minSdkVersion 15
          targetSdkVersion 27
          versionCode 1
          versionName "1.0"
          testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
      }
      buildTypes {
          release {
              minifyEnabled false
              proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
          }
      }
  }
  
  dependencies {
      compile fileTree(dir: 'libs', include: ['*.jar'])
      androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
          exclude group: 'com.android.support', module: 'support-annotations'
      })
      compile 'com.android.support:appcompat-v7:27.+'
      testCompile 'junit:junit:4.12'
  }
  </code></pre>
  
  <p>activity_main.xml:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:tools="http://schemas.android.com/tools"
      android:id="@+id/activity_main"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:paddingBottom="@dimen/activity_vertical_margin"
      android:paddingLeft="@dimen/activity_horizontal_margin"
      android:paddingRight="@dimen/activity_horizontal_margin"
      android:paddingTop="@dimen/activity_vertical_margin"
      tools:context="com.chanfool21.firstapp.MainActivity"&gt;
  
      &lt;TextView
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:text="Hello World!" /&gt;
  &lt;/RelativeLayout&gt;
  </code></pre>