Dynamically created button doesn't apply style correctly

Question

I defined a style in themes.xml:

<style name="ButtonStyle" parent="Widget.MaterialComponents.Button">
    <item name="android:layout_width">match_parent</item>
    <item name="android:layout_height">240dp</item>
</style>

I then apply it to some of the buttons, in activity_main.xml:

<Button
    android:id="@+id/btn_folder0"
    style="@style/ButtonStyle"
    android:text="@string/folder0" />

<Button
    android:id="@+id/btn_folder1"
    style="@style/ButtonStyle"
    android:text="@string/folder1" />

Now I want to dynamically create a button and apply the same style, like this (in MainActivity.kt):

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)

    val layout = findViewById<LinearLayout>(R.id.layout_folders)
    val btn = Button(this, null, R.style.ButtonStyle)
    btn.text = "new button"
    layout.addView(btn)
}

However the dynamically created button doesn't have the style. It looks like:

I have also tried val btn = Button(ContextWrapper(this, R.style.ButtonStyle)) which leads to a different result but again not the same style as the upper two buttons.

What am I missing? How can I apply the style to a dynamically created button?

Answer 1

You are creating the button using Button(Context context, AttributeSet attrs, int defStyleAttr)

According to the docs:

This constructor allows a Button subclass to use its own class-specific base style from a theme attribute when inflating.

To apply your style to the button, you should use Button(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) instead.

Answer 2

Width and height can't be set via themes at runtime. You need to set them in layout params, and use that when you add it to the parent view.