title: How to set background to black
body: <p>Whie I set activity theme to light.  </p>
  
  <pre><code>android:theme="@android:style/Theme.Light.NoTitleBar"
  </code></pre>
  
  <p>And I set layout background to 0x000000.<br>
  It will display gray.<br>
  How to make it to　black?　</p>
  
  <p>I set below line to color.xml.<br>
    #000000
  And set as below:  </p>
  
  <pre><code>ll.setBackgroundColor(R.color.black);
  </code></pre>
  
  <p>ll is LinearLayout.  </p>