title: How to make canvas transparent in Android?
body: <p>I want to make the drawing surface of my app transparent so that the my app can look like the user can draw on top of my background image, I have the following XML:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
      android:orientation="vertical"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:background="@drawable/bg2"
  &gt;
  
      &lt;com.almondmendoza.drawings.DrawingSurface
          android:layout_width="fill_parent"
          android:layout_height="200dip"
          android:id="@+id/drawingSurface"
      /&gt;
  
      &lt;LinearLayout
          android:orientation="horizontal"
          android:layout_width="wrap_content" 
          android:layout_height="wrap_content" 
          android:layout_alignParentBottom="true" &gt;
  
          &lt;Button
                  android:layout_height="wrap_content"
                  android:layout_width="wrap_content"
                  android:text="OK"
                  android:onClick="onClick"
                  android:id="@+id/colorGreenBtn" /&gt;
          &lt;Button
                  android:layout_height="wrap_content"
                  android:layout_width="wrap_content"
                  android:text="Scratch"
                  android:onClick="onClick"
                  android:id="@+id/colorRedBtn" /&gt;
          &lt;Button
                  android:layout_height="wrap_content"
                  android:layout_width="wrap_content"
                  android:text="Minor Scratch"
                  android:onClick="onClick"
                  android:id="@+id/colorBlueBtn" /&gt;
          &lt;Button
                  android:layout_height="wrap_content"
                  android:layout_width="wrap_content"
                  android:text="Dent"
                  android:onClick="onClick"
                  android:id="@+id/dentBtn" /&gt;
          &lt;Button
                  android:layout_height="wrap_content"
                  android:layout_width="wrap_content"
                  android:text="Minor Dent"
                  android:onClick="onClick"
                  android:id="@+id/minorDentBtn" /&gt;
          &lt;Button
                  android:layout_height="wrap_content"
                  android:layout_width="wrap_content"
                  android:text="Damaged"
                  android:onClick="onClick"
                  android:id="@+id/damagedBtn" /&gt;
          &lt;Button
                  android:layout_height="wrap_content"
                  android:layout_width="wrap_content"
                  android:text="Undo"
                  android:onClick="onClick"
                  android:id="@+id/undoBtn" /&gt;
          &lt;Button
                  android:layout_height="wrap_content"
                  android:layout_width="wrap_content"
                  android:text="Redo"
                  android:onClick="onClick"
                  android:id="@+id/redoBtn" /&gt;
          &lt;Button
                  android:layout_height="wrap_content"
                  android:layout_width="wrap_content"
                  android:text="Save"
                  android:onClick="onClick"
                  android:id="@+id/saveBtn" /&gt;
  
      &lt;/LinearLayout&gt;
  
  &lt;/RelativeLayout&gt;
  </code></pre>
  
  <p>The ouput of the XML code above is like this:</p>
  
  <p><img src="https://i.stack.imgur.com/eMDl0.png" alt="enter image description here"></p>
  
  <p>As you can see the drawing surface is the black part of the screen. I want this to be transparent, is that possible?</p>
  
  <p>Thanks a lot for any help! :)</p>