Android Marshmallow - Custom seekbar progress bar not showing

Question

I'm trying to customize my seekbar like this:

On API level < 23, progress line is visible even if progress of seekbar equals to 0. But on API level = 23, I have strange issue: progress line not showing in the same conditions =/ I want to see this line, because it is clarifying borders of usage my seekbar.

My seek_bar_progress_bar.xml:

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:id="@android:id/background" android:drawable="@drawable/seek_bar_track" />
    <item android:id="@android:id/secondaryProgress">
        <scale
            android:drawable="@drawable/seek_bar_track"
            android:scaleWidth="100%" />
    </item>
    <item android:id="@android:id/progress">
        <scale
            android:drawable="@drawable/seek_bar_track"
            android:scaleWidth="100%" />
    </item>
</layer-list>

My style.xml:

<style name="seek_bar_style" parent="android:Widget.Holo.Light.SeekBar">
    <item name="android:progressDrawable">@drawable/seek_bar_progress_bar</item>
    <item name="android:indeterminateDrawable">@drawable/seek_bar_progress_bar</item>
    <item name="android:thumb">@drawable/seek_bar_thumb_selector</item>
</style>

Thanks in advance!

Answer 1

Well, I really don't know, why my progress bar line not shows on Android 6 devices, if my drawables for seek_bar_track was simple .png images. But when I changed this format into .9.png (with SDK tool draw9patch) - it works.

Summary - I transformed my .png images for seek_bar_track to .9.png format, and it helped me into solve my problem.