自定义seekbar拇指在Lollipop API21上不透明

这是我的搜索栏:

<SeekBar
    android:id="@+id/seek1"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_margin="10dp"
    android:progressDrawable="@drawable/style_progressbar"
    android:thumb="@drawable/style_progressbar_circle"
    android:progress="20" />

这是 style_progressbar.xml :

<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:id="@android:id/background">
        <shape android:shape="rectangle" >
            <corners android:radius="5dp" />
            <gradient
                android:angle="270"
                android:endColor="@color/gris_hint"
                android:startColor="@color/gris_hint" />
        </shape>
    </item>
    <item android:id="@android:id/secondaryProgress">
        <clip>
            <shape android:shape="rectangle" >
                <corners android:radius="5dp" />
                <gradient
                    android:angle="270"
                    android:endColor="@color/gris"
                    android:startColor="@color/gris" />
            </shape>
        </clip>
    </item>
    <item android:id="@android:id/progress">
        <clip>
            <shape android:shape="rectangle" >
                <corners android:radius="5dp" />
                <gradient
                    android:angle="270"
                    android:endColor="@color/gris"
                    android:startColor="@color/gris" />
            </shape>
        </clip>
    </item>
</layer-list>

这是style_progressbar_circle.xml

And this is style_progressbar_circle.xml

<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:drawable="@drawable/red_scrubber_control_disabled_holo" android:state_enabled="false"/>
    <item android:drawable="@drawable/red_scrubber_control_pressed_holo" android:state_pressed="true"/>
    <item android:drawable="@drawable/red_scrubber_control_focused_holo" android:state_selected="true"/>
    <item android:drawable="@drawable/red_scrubber_control_normal_holo"/>
</selector>    

这就是我在棒棒糖中看到的方式

This is how I see it in Lollipop

这是它的外观，这是在Kitkat和更低版本上的外观.

This is how it should look, this is how it looks on Kitkat and lower versions.

有什么主意吗?我在Lollipop上的布局存在一些问题，但这是我自己无法解决的唯一问题.

Any idea? I've got some issues with layouts on Lollipop but this is the only one I can't solve for my own.