android - onDraw 在自定义 View 中的 onMeasure 之前被调用

Question

我在自定义 View 中有两个方法，onMeasure 和 onDraw。我有一个函数用于从源设置数据并使用使 View 函数无效来重绘 View 。我使用 onMeasure 来获取计算所需的 View 宽度。但是当我使用无效函数时，首先调用 onDraw，然后调用我的 onMeasure。因此我的 View 宽度始终为 0px。

我试过调用 requestLayout() 然后 invalidate() 重绘 View

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

    val pointY = 15.px.toFloat()
    var pointX = oneCellWidth.toFloat() / 2f

    totalDays.forEach { day ->
        val isWorkedDay = workedDays.filter { it.date == day.date }.size
        if (isWorkedDay > 0) {
            canvas?.drawCircle(pointX, pointY, 8f, circlePaint)
        }
        pointX += oneCellWidth
    }
}

fun submitData(totalDays: List<Day>, workedDays: List<WorkedDateAndTime>, color: Int) {
    this.totalDays = totalDays
    this.workedDays = workedDays
    circlePaint.color = color
    oneCellWidth = viewWidth / totalDays.size
    invalidate()
}

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

    val widthMode = MeasureSpec.getMode(widthMeasureSpec)
    val widthSize = MeasureSpec.getSize(widthMeasureSpec)

    if (widthMode == MeasureSpec.EXACTLY) {
        viewWidth = widthSize

    }
}

需要 viewWidth 不具有 View 宽度值。

Answer 1

我猜问题的发生是因为您在调用 View.invalidate() 之前阅读了 viewWidth。因此，当您读取 viewWidth 时，它仍然具有旧值。

因此，我建议进行以下更改:

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

    oneCellWidth = viewWidth / totalDays.size // Add this
    val pointY = 15.px.toFloat()
    var pointX = oneCellWidth.toFloat() / 2f

    totalDays.forEach { day ->
        val isWorkedDay = workedDays.filter { it.date == day.date }.size
        if (isWorkedDay > 0) {
            canvas?.drawCircle(pointX, pointY, 8f, circlePaint)
        }
        pointX += oneCellWidth
    }
}

fun submitData(totalDays: List<Day>, workedDays: List<WorkedDateAndTime>, color: Int) {
    this.totalDays = totalDays
    this.workedDays = workedDays
    circlePaint.color = color
    // oneCellWidth = viewWidth / totalDays.size --> Remove this
    requestLayout() // Add this. invalidate only request re-draw. requestLayout will request to re-measure
    invalidate()
}

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

    val widthMode = MeasureSpec.getMode(widthMeasureSpec)
    val widthSize = MeasureSpec.getSize(widthMeasureSpec)

    if (widthMode == MeasureSpec.EXACTLY) {
        viewWidth = widthSize
    }
}

这样，您就可以避免在重新执行 onMeasure 之前读取 viewWidth 的问题。在这些更改之后，您在 onDraw 期间读取 viewWidth，它始终在 onMeasure 之后执行(如果您调用 requestLayout()当然。