RatioImageView.kt

/**
 * Makes the height match the width, using the set ratio
 */
class RatioImageView : ImageView {
    private var ratio = 1f

    constructor(context: Context) : this(context, null, 0)
    constructor(context: Context, attrs: AttributeSet?) : this(context, attrs, 0)
    constructor(context: Context, attrs: AttributeSet?, defStyleAttr: Int) : super(context, attrs, defStyleAttr)

    /**
     * w:h
     */
    fun setRatio(r: Float) {
        ratio = r
        requestLayout()
    }

    override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
        // Return height as width to force square
        val width = MeasureSpec.getSize(widthMeasureSpec)
        val height = (width.toFloat() / ratio).toInt()
        val wSpec = MeasureSpec.makeMeasureSpec(width, MeasureSpec.EXACTLY)
        val hSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY)
        super.onMeasure(wSpec, hSpec)
    }

}