A easy way to set onMeasure function. Of course if you wanna customize more, you can do more things.

README.kt

override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
    // Measure all of children's width & height.
    this.measureChildren(widthMeasureSpec, heightMeasureSpec)
    // Measure width & height of this view_group's layout(layout_width or layout_height will be `match_parent`
    // no matter what we set `wrap_content` or `match_patent` when we're using getDefaultSize).
    // We'll reset this method by another way for achieving `wrap_content`.
    val mini = minOf(getDefaultSize(suggestedMinimumWidth, widthMeasureSpec), getDefaultSize(suggestedMinimumHeight, heightMeasureSpec))
    this.setMeasuredDimension(mini, mini)
}