title: What is the difference between android:contentDescription="@null" and tools:ignore="ContentDescription"? Use android:importantForAccessibility="no"?
body: <p>Take this android layout XML snippet for example:</p>
  
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  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;ImageView
          android:layout_width="0dp"
          android:layout_height="match_parent"
          android:layout_gravity="center"
          android:layout_weight="1"
          android:padding="10dp"
          app:srcCompat="@drawable/bitcoin"
          android:contentDescription="@null"
          android:importantForAccessibility="no"
          tools:ignore="ContentDescription" /&gt;</code></pre>
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  <p>What is the difference between <code>android:contentDescription="@null"</code> and <code>tools:ignore="ContentDescription"?</code></p>
  
  <p>I know both of them are used to indicate that a certain non-textual element carries no meaning and is only meant for decoration. Is there an advantage of using one over the other, should I use both, is it preference, or is one considered better and newer than the other?</p>
  
  <p>Also, should I use <code>android:importantForAccessibility="no"</code> or is using all three attributes/properties simply overkill?</p>