title: Fix android studio warning about `layout_marginHorizontal`
body: <p>I'm getting these warnings in my android build.</p>
  <pre class="lang-none prettyprint-override"><code>Warning:(19, 9) Attribute `layout_marginVertical` is only used in API level 26 and higher (current min is 24)
  Warning:(20, 9) Attribute `layout_marginHorizontal` is only used in API level 26 and higher (current min is 24)
  </code></pre>
  <p>Clearly our app's layouts make use of <code>layout_marginVertical</code> and <code>layout_marginHorizontal</code> attributes, which were introduced in API level 26. The warning makes it sound like these attributes won't work on level 24 devices, but indeed they work perfectly. I would like to understand why I'm getting these warnings, despite there seeming to be nothing wrong.</p>
  <p>One obvious solution is to use the &quot;longhand&quot;: <code>marginTop</code> and <code>marginBottom</code> instead of <code>marginVertical</code>, but I'm hoping to continue to use these &quot;short&quot; parameters if possible, to improve readability and reduce repetition.</p>
  <p>Were these attributes undocumented for level 24? Or is there some kind of backward compatibility at play? If so, why the warning?</p>
  <p>We are using:</p>
  <pre><code>&lt;uses-sdk
      android:minSdkVersion=&quot;24&quot;
      android:targetSdkVersion=&quot;26&quot; /&gt;
  </code></pre>
  <hr />
  <p><strong>Update:</strong> Setting <code>targetSdkVersion=&quot;24&quot;</code> seems to fix the warnings, and the desired margins continue to work. This solves my immediate problem, but I'm left confused about why a level 26 feature works on level 24, and why targeting level 26 causes warnings. What do I do if I want to target level 26?</p>