MaskableTextView

MaskableTextView.kt

import android.content.Context
import android.graphics.Canvas
import android.graphics.Paint
import android.graphics.PorterDuff
import android.graphics.PorterDuffXfermode
import android.graphics.drawable.Drawable
import android.support.v7.widget.AppCompatTextView
import android.util.AttributeSet

class MaskableTextView @JvmOverloads constructor(
        context: Context,
        attrs: AttributeSet? = null,
        defStyleAttr: Int = android.R.attr.textViewStyle
) : AppCompatTextView(context, attrs, defStyleAttr) {

    private val maskPaint = Paint().apply {
        xfermode = PorterDuffXfermode(PorterDuff.Mode.MULTIPLY)
    }

    var maskDrawable: Drawable? = null
        set(value) {
            field = value
            value?.state = drawableState
            invalidate()
        }

    override fun drawableStateChanged() {
        super.drawableStateChanged()
        maskDrawable?.let { if (it.isStateful && it.setState(drawableState)) invalidate() }
    }

    override fun onDraw(canvas: Canvas) {
        canvas.saveLayer(null, null, Canvas.ALL_SAVE_FLAG)
        super.onDraw(canvas)
        maskDrawable?.let {
            canvas.saveLayer(null, maskPaint, Canvas.ALL_SAVE_FLAG)
            it.setBounds(0, 0, canvas.width, canvas.height)
            it.draw(canvas)
            canvas.restore()
        }
        canvas.restore()
    }

    init {
        val arr = context.obtainStyledAttributes(attrs, R.styleable.MaskableTextView, defStyleAttr, 0)
        maskDrawable = arr.getDrawable(R.styleable.MaskableTextView_maskDrawable)
        arr.recycle()
    }
}