title: zIndex doesot work on Card of native-base - react native
body: <p>I'm using <code>native-base</code>.
  this is my code:</p>
  
  <pre><code>                     &lt;View style={{width:'100%',height:45}}&gt;
                        &lt;Card style={{position:'absolute',zIndex:90,paddingTop: 0, marginRight:10,width: '100%', alignSelf: 'center',borderRadius:10,padding:10,height:45 }}&gt;
                          &lt;CardItem style={{ position:'absolute', zIndex:1,backgroundColor: '#fff', height: 45, width: '100%', paddingTop: 0, paddingBottom: 0, justifyContent: 'flex-end' }}&gt;
                            &lt;TouchableOpacity onPress={() =&gt; this.onClickSubs(sub)} style={{height:'100%',width:'100%'}}&gt;
                              &lt;Text onPress={() =&gt; this.onClickSubs(sub)} style={{ textAlign: 'center', fontSize: 16, color: colorConstants.GRAY_LIGHT_COLOR }}&gt;{sub.title}&lt;/Text&gt;
                            &lt;/TouchableOpacity&gt;
                          &lt;/CardItem&gt;
                        &lt;/Card&gt;
                        &lt;View style={{position:'absolute',zIndex:999,right:0,width:20,height:20,borderRadius:10,borderWidth:2,borderColor:'#fff',backgroundColor:colorConstants.PRIMARY_COLOR,alignSelf:'center',justifyContent:'center',alignItems:'center'}}&gt;
                        &lt;/View&gt; //circle view
  
                        &lt;/View&gt;
  </code></pre>
  
  <p>but my circle view is background of <code>Card</code>:</p>