ImageSpan not working on Android 5

By default, in Material buttons are styled to show text in all-caps. However, there is a bug in the AllCapsTransformationMethod used for capitalization that causes it to discard Spannable data.

You can override the default button styling and disable all-caps by specifying android:textAllCaps="false" on your Button.

<Button
    ...
    android:textAllCaps="false" />

have a look here

Your code related to working with Spannables is ok. You can check it by setting text for TextView.

The problem is in material design of button on Android 5.0.

<style name="Widget.Material.Button">
    <item name="background">@drawable/btn_default_material</item>
    <item name="textAppearance">?attr/textAppearanceButton</item>
    <item name="minHeight">48dip</item>
    <item name="minWidth">88dip</item>
    <item name="stateListAnimator">@anim/button_state_list_anim_material</item>
    <item name="focusable">true</item>
    <item name="clickable">true</item>
    <item name="gravity">center_vertical|center_horizontal</item>
</style>

There are two solution.

The first one is just use TextView as your button and setText with image to it.

For another (and may be more correct) you need to extend button style (Widget.Material.Button) in next way:

<style name="BtnStyle" parent="android:Widget.Material.Button">
    <item name="android:textAppearance">@null</item>
</style>

Then in your layout:

<Button
    android:id="@+id/test2"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="Test"
    style="@style/BtnStyle"/>

After you'll do it you should see the images in the button.

Don't forget for Android version that is lower than 5.0 you should create BtnStyle too, but in other resource directory (res/values-v14/style.xml).

One thing to note, drawable vectors won't work, you must either have a drawable which is a png or jpeg or pass to ImageSpan bitmap instead