title: buttons background images stretched (wrap_content or dp usage)
body: <p>i'm setting background images to my custom buttons. I made a screenshot for my app and mentioned that when i'm using "wrap_content" for the width and height of the button, the button is stretched. When i'm fixing a size in dp, it will appear nice ( ex: in my mdpi folder i have 48x48px icons, so i put 48dp in width and height). Can you please explain me why?</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:id="@+id/definition_layout"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"
  android:orientation="vertical"
  android:padding="5dp"
  android:layout_alignParentTop="true" &gt;
  
  &lt;LinearLayout
      xmlns:android="http://schemas.android.com/apk/res/android"
      android:id="@+id/buttons"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:orientation="horizontal"
      android:padding="5dp" &gt;
  
      &lt;Button
          android:id="@+id/addToFavorites"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_margin="5dp"
          android:background="@drawable/favorites_button" /&gt;
  
      &lt;Button
          android:id="@+id/fontup"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_margin="5dp"
          android:background="@drawable/fontup_button" /&gt;
  
      &lt;Button
          android:id="@+id/fontdown"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_margin="5dp"
          android:background="@drawable/fontdown_button" /&gt;
  
      &lt;Button
          android:id="@+id/comment"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_margin="5dp"
          android:background="@drawable/comment_button" /&gt;
  
      &lt;Button
          android:id="@+id/speak"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_margin="5dp"
          android:background="@drawable/speak_button" /&gt;
      &lt;/LinearLayout&gt;
  
      &lt;ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
          android:layout_width="fill_parent" 
          android:layout_height="fill_parent"
          android:layout_below="@id/buttons"&gt;
  
      &lt;LinearLayout
          android:layout_width="fill_parent"
          android:layout_height="wrap_content"&gt;
  
      &lt;ImageView
          android:id="@+id/image_frame"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content" /&gt;
      &lt;WebView
          android:id="@+id/webView1"
          android:layout_below="@id/image_frame"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content" /&gt;
      &lt;/LinearLayout&gt;
      &lt;/ScrollView&gt;
  
      &lt;/RelativeLayout&gt;
  </code></pre>
  
  <p>The code above shows my XML file. You can check this link to view a screenshot for my problem: 
  <a href="https://www.dropbox.com/s/phnxt5p335ltqef/buttons_icon_altered.png" rel="noreferrer">https://www.dropbox.com/s/phnxt5p335ltqef/buttons_icon_altered.png</a></p>