Android: TextView transparent png as background resource not working

Question

I have a simple TextView inside a CardView (which acts as a button):

<androidx.cardview.widget.CardView
    android:id="@+id/cvTestType"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_margin="20dp"
    app:cardCornerRadius="5dp"
    app:cardElevation="10dp">

    <TextView
        android:id="@+id/tvTestType"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:textStyle="bold"
        android:textSize="15sp" />

</androidx.cardview.widget.CardView>

I'm trying to set a transparent png background to the button as follows:

private fun TextView.setTestTypeTextView(testType: TestTypeDTO) {
    val buttonFontSize = this.context.prefsByScreenDensity()[3]
    this.height = buttonsHeight
    this.text = testType.testTypeName.uppercase(Locale.getDefault())
    this.setTextSize(TypedValue.COMPLEX_UNIT_SP, buttonFontSize.toFloat())
    this.setTextColor(Color.parseColor(props.appearance.colors.appColor))
    
    this.setBackgroundResource(R.drawable.button_act_background)
}

And the problem is, as it can be seen in the screenshot, that using a transparent png as a background is not working, it just displays the button in white with no background at all, it only works when using a non-transparent background.

The PNG is created (and exported) with Gimp and it can be perfectly seen using the Android Studio preview.

Any help?

Edit 1:

Tried different transparent PNGs and noticed that with another PNG I can see the drawing, but the background is still white.

Answer 1

The root cause is that you are seeing the background of your CardView which seems to be white with your Theme. You can change it using app:cardBackgroundColor="@color/yourColor".