Resized text view

NumberView.kt

package com.example.android.basictransition

import android.content.Context
import android.graphics.Canvas
import android.graphics.Color
import android.graphics.Paint
import android.graphics.Rect
import android.support.annotation.ColorInt
import android.util.AttributeSet
import android.util.TypedValue
import android.view.View

class NumberView : View {

    // <editor-fold desc="Properties">
    var letterSpacing
        get() = paint.letterSpacing
        set(value) {
            paint.letterSpacing = value
            requestLayout()
            invalidate()
        }
    var textColor = Color.BLACK
        @ColorInt get
        set(@ColorInt value) {
            field = value
            invalidate()
        }
    var text: String = ""
        set(value) {
            field = value
            requestLayout()
            invalidate()
        }
    // </editor-fold>

    private val paint = Paint()
    private val textRect = Rect()
    private val defaultTextSize = TypedValue.applyDimension(
            TypedValue.COMPLEX_UNIT_SP, 12f, resources.displayMetrics)

    private var measuredTextSize = 0f

    constructor(context: Context) : super(context) {
        init(context)
    }

    constructor(context: Context, attrs: AttributeSet?) : super(context, attrs) {
        init(context, attrs)
    }

    constructor(context: Context, attrs: AttributeSet?, defStyleAttr: Int) :
            super(context, attrs, defStyleAttr) {
        init(context, attrs, defStyleAttr)
    }

    @Suppress("UNUSED_PARAMETER")
    private fun init(
            context: Context,
            attrs: AttributeSet? = null,
            defStyleAttr: Int = 0,
            defStyleRes: Int = 0
    ) {
        context.theme.obtainStyledAttributes(
                attrs,
                R.styleable.NumberView,
                0,
                0
        ).apply {
            try {
                letterSpacing = getFloat(R.styleable.NumberView_android_letterSpacing, 0.1f)
                textColor = getColor(R.styleable.NumberView_android_textColor, textColor)
                text = getString(R.styleable.NumberView_android_text) ?: text
            } finally {
                recycle()
            }
        }

        paint.isAntiAlias = true
        paint.color = textColor
        paint.textSize = defaultTextSize
        paint.textAlign = Paint.Align.CENTER
    }

    override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec)

        paint.textSize = defaultTextSize
        paint.getTextBounds(text, 0, text.length, textRect)

        measuredTextSize = calculateTextSize(measuredWidth, measuredHeight)
        paint.textSize = 0f
    }

    private fun calculateTextSize(width: Int, height: Int): Float {
        if (textRect.width() == 0 || textRect.height() == 0) {
            return 0f
        }

        val ratio = Math.min(
                (width - height / 3f) / textRect.width(),
                (height - height / 3f) / textRect.height())

        return defaultTextSize * ratio
    }

    // Fix text shake during animation
    private fun filteredValue(requested: Float, current: Float, measured: Float): Float {
        return when {
            current == 0f || requested == measured -> requested
            requested < measured -> Math.max(requested, current)
            else -> Math.min(requested, current)
        }
    }

    override fun onDraw(canvas: Canvas) {
        super.onDraw(canvas)

        if (!text.isEmpty()) {
            val textSize = calculateTextSize(width, height)

            paint.color = textColor
            paint.textSize = filteredValue(textSize, paint.textSize, measuredTextSize)

            val descent = paint.fontMetrics.descent
            val ascent = paint.fontMetrics.ascent

            val baseline = height / 2f + (descent - ascent) / 2f - descent
            canvas.drawText(text, 0, text.length, width / 2f, baseline, paint)
        }
    }
}