I removed all lines mentioned below from /res/values-v21/styles.xml and now it is working fine.
<item name="android:windowDrawsSystemBarBackgrounds">true</item>
<item name="android:statusBarColor">@android:color/transparent</item>
<item name="windowActionBar">false</item>
<item name="android:windowDisablePreview">true</item>
<item name="windowNoTitle">true</item>
<item name="android:fitsSystemWindows">true</item>