Android自定义颜色渐变的拖动条

<shape    xmlns:android="http://schemas.android.com/apk/res/android"    android:shape="rectangle"    android:useLevel="false">    <solid android:color="#252B39"/>    <corners android:radius="5dp" />    <size android:width="50dp"        android:height="5dp"/>    <gradient        android:startColor="#FFA200"        android:endColor="#ffffff"        android:angle="0"        /></shape>

  <SeekBar            android:id="@+id/seekbar_light"            android:layout_width="fill_parent"            android:layout_height="wrap_content"            android:layout_gravity="center"            android:layout_marginLeft="5dp"            android:layout_marginRight="5dp"            android:max="255"            android:progress="0"            android:progressDrawable="@drawable/shape_seekbar_light"            android:thumb="@drawable/seekbar_thumb"            android:visibility="gone"            android:thumbOffset="2dp" />