title: Dialog displaying white background when using a png with transparency as a background
body: <p>I created a background for a Dialog with Gimp, and it's a PNG with transparency and transparent background. If I display it on a ImageView it's fine and the background is transparent.</p>
  <pre><code>&lt;ImageView
      android:src=&quot;@drawable/test&quot;
  </code></pre>
  <p>But if I display it as a background of the LinearLayout of my Dialog, then, a white background is displayed instead of the transparency (alpha channel) of the image.</p>
  <pre><code>&lt;LinearLayout xmlns:android=&quot;http://schemas.android.com/apk/res/android&quot;
      android:background=&quot;@drawable/test&quot;
  
  final Dialog dialog = new Dialog(context);
          dialog.setContentView(R.layout.xmldialog);
  </code></pre>
  <p>This is the PNG:</p>
  <p><a href="https://i.stack.imgur.com/7LYGQ.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/7LYGQ.png" alt="enter image description here" /></a></p>
  <p>What should be done to get the alpha channel and not a white background below the image I created when I use as a background of a the LinearLayout of a Dialog? I'm sure it's a problem with the dialog. Something must be setted to true.</p>