TextView 竖直显示文字，并做对应的旋转，使他在布局中也是正确的大小

import android.content.Context
import android.graphics.Canvas
import android.util.AttributeSet
import android.view.Gravity
import androidx.appcompat.widget.AppCompatTextView


class VerticalTextView(context: Context, attrs: AttributeSet) :
    AppCompatTextView(context, attrs) {
    private var topDown = false
    init {
        val gravity = gravity
        topDown =
            if (Gravity.isVertical(gravity) && gravity and Gravity.VERTICAL_GRAVITY_MASK == Gravity.BOTTOM) {
                setGravity(gravity and Gravity.HORIZONTAL_GRAVITY_MASK or Gravity.TOP)
                false
            } else true
    }

    override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
        super.onMeasure(heightMeasureSpec, widthMeasureSpec)
        setMeasuredDimension(measuredHeight, measuredWidth)
    }

    override fun onDraw(canvas: Canvas) {
        val textPaint = paint
        textPaint.setColor(currentTextColor)
        textPaint.drawableState = drawableState
        canvas.save()

        //默认为文字朝右，即旋转了90度
        //设置android:gravity="bottom"时，他会文字朝向左，即旋转了270度
        if (topDown) {
            canvas.translate(width.toFloat(), 0f)
            canvas.rotate(90f)
        } else {
            canvas.translate(0f, height.toFloat())
            canvas.rotate(-90f)
        }
        canvas.translate(getCompoundPaddingLeft().toFloat(), getExtendedPaddingTop().toFloat())
        layout.draw(canvas)
        canvas.restore()
    }
}