title: Updating External Libraries in Android Studio
body: <p>I'm fairly new to Android development, so apologies if this is obvious. I've searched quite a lot but am unable to resolve my issue.</p>
  <p>In my build.gradle file I have the following section:</p>
  <pre><code>dependencies {
      implementation fileTree(dir: 'libs', include: ['*.jar'])
      implementation 'com.android.support:appcompat-v7:26.1.0'
      implementation 'com.android.support.constraint:constraint-layout:1.1.0'
      implementation 'com.android.support:design:26.1.0'
      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'
      implementation 'com.google.firebase:firebase-auth:15.1.0'
      implementation 'com.google.android.gms:play-services-auth:15.0.1'
      implementation 'com.wdullaer:materialdatetimepicker:3.2.2'
  }
  </code></pre>
  <p>However the line <code>implementation 'com.android.support:appcompat-v7:26.1.0'</code> is showing with a red squiggly line underneath and displaying the following message:</p>
  <blockquote>
  <p>All com.android.support libraries must use the exact same version specification (mixing versions can lead to runtime crashes). Found versions 26.1.0, 25.3.1. Examples include com.android.support:animated-vector-drawable:26.1.0 and com.android.support:support-v13:25.3.1 less... (⌘F1)</p>
  <p>There are some combinations of libraries, or tools and libraries, that are incompatible, or can lead to bugs. One such incompatibility is compiling with a version of the Android support libraries that is not the latest version (or in particular, a version lower than your targetSdkVersion).</p>
  </blockquote>
  <p>I am unable to find out how to solve this issue. Building the project works fine and does not report any errors. I've tried doing <code>File &gt; Invalidate Caches / Restart</code> but to no avail.</p>
  <p>After doing a bit of searching I read that I can add <code>implementation 'com.android.support:support-v4:26.1.0'</code> to the build.gradle file and it should fix it, however the same error shows even after syncing.</p>
  <p>This is an old project I made sometime last year and it doesn't have a lot in it, but I thought it would be better to learn how to resolve this issue rather than just creating a new project to get around it.</p>