Android自定义有限制区域图例角度自识别涂鸦工具类

class SignatureView constructor(context: Context?, attrs: AttributeSet? = null) :
    View(context, attrs, 0) {
    private lateinit var paint: Paint
    private var mWidth = 0 //父类宽度
    private var mHeight = 0//父类高度
    override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec)
        mWidth = MeasureSpec.getSize(widthMeasureSpec)
        mHeight = MeasureSpec.getSize(heightMeasureSpec)
        paint = Paint()
        //设置抗锯齿
        paint.isAntiAlias = true
        //设置签名笔画样式
        paint.style = Paint.Style.STROKE
        setMeasuredDimension(mWidth, mHeight)
   }
    override fun onDraw(canvas: Canvas) {
        super.onDraw(canvas)
        ......
    }
}

override fun onTouchEvent(event: MotionEvent): Boolean {
    super.onTouchEvent(event)
}

//收集用户绘制的点
private var allPoints: MutableList<Point> = ArrayList()
val p = Point(event.x.toInt(), event.y.toInt())
when (event.action) {
    MotionEvent.ACTION_DOWN -> {
        //用户按下，表示重新开始保存点
        allPoints.clear()
        allPoints.add(p)
    }
    MotionEvent.ACTION_UP -> {
        postInvalidate() //重绘图像
    }
    MotionEvent.ACTION_MOVE -> {
        allPoints.add(p)
        postInvalidate() //子线程可刷新
    }
}

val first = allPoints[0] //第一个点
val last = allPoints[allPoints.size-1] //最后一个点
canvas.drawLine(first.x.toFloat(),first.y.toFloat(),last.x.toFloat(),last.y.toFloat(),paint)

//用于画完图后的显示，在抬起时，添加来自于allPoints的所有点的数据
private var allList: MutableList<List<Point>> = ArrayList()
//用于划线过程中的显示，当集合allList存储后，清空本集合中所有数据
private var allPoints: MutableList<Point> = ArrayList()
override fun onTouchEvent(event: MotionEvent): Boolean {
    super.onTouchEvent(event)
    val p = Point(event.x.toInt(), event.y.toInt())
    when (event.action) {
        MotionEvent.ACTION_DOWN -> {
            //用户按下，表示重新开始保存点
            allPoints = ArrayList()
            allPoints.add(p)
        }
        MotionEvent.ACTION_UP -> {
            //用户松开
            allList.add(allPoints)
            allPoints = ArrayList() //添加集合后，清除子集合
            postInvalidate() //重绘图像
        }
        MotionEvent.ACTION_MOVE -> {
            allPoints.add(p)
            postInvalidate() //子线程可刷新
        }
    }
    return true
}
//上一步（清除本次绘画）
fun clearLatestData() {
    if (allList.size > 0) {
        allList.removeAt(allList.size - 1)
        paints.removeAt(paints.size - 1)
    }
    postInvalidate()
}

//重置（清除所有绘画）
fun clearAllData() {
    allList.clear()
    postInvalidate()
}