title: how to change key background of any key in Android soft keyboard
body: <p>I want to have some of my keys in the keyboard different from others. </p>
  
  <p>For example,like shift, delete, space key in below photo:</p>
  
  <p><img src="https://i.stack.imgur.com/nMR5i.png" alt="enter image description here"></p>
  
  <p>According to the reference documents from google. We can change key's background by use "<code>android:keybackground=@drawable/xxx</code>" in "<code>input.xml</code>", but it change background of all keys in keyboard. </p>
  
  <p>Although "android:keyicon" in qwerty.xml can have single key changed,but it only replace the label. Meanwhile, use "<code>android:keyicon</code>" , the image can not cover entire key , the image will be a litte bit smaller than the key background.</p>
  
  <p><strong>What's the correct way to change background of some keys?</strong></p>