自定義視圖未在 BottomSheetDialogFragment 中繪制，有時在無效后調用 onSizeChanged

Question

我正在開發一個自定義圖形視圖，顯示在底部工作表對話框片段中並且它沒有繪制，當我添加數據並在調用onSizeChanged() invalidate()時。 這種情況有時會發生，我不知道如何解決。

我將數據添加到我的 BottomSheetDialogFragment 的onViewCreated(...)中，即 LiveData，因此觀察者調用 ChartView 的setDataPoints()肯定需要一些時間。

我還在兩個正常片段中使用圖表，它在那里工作正常。

我的自定義視圖：

class MonthlyTrendChart @JvmOverloads constructor(context: Context, attrs: AttributeSet? = null, defStyleAttr: Int = 0) : View(context, attrs, defStyleAttr) {

    //region Variables

    private val data = mutableListOf<DateDataPoint>()
    private val points = mutableListOf<PointF>()

    private val path = Path()

    private val pathPaint: Paint

    //endregion

    //region Constructor

    init {
        pathPaint = Paint().apply {
            isAntiAlias = true
            color = Color.WHITE
            strokeWidth = 5.0f
            style = Paint.Style.STROKE
        }

        setWillNotDraw(false)
    }

    //endregion

    //region View

    override fun onSizeChanged(w: Int, h: Int, oldw: Int, oldh: Int) {
        super.onSizeChanged(w, h, oldw, oldh)

        println("MB: onSizeChanged: ${data.size}")
    }

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

        computePath()

        canvas?.drawPath(path, pathPaint)
    }

    //endregion

    //region Methods

    fun setDataPoints(dataPoints: List<DateDataPoint>) = GlobalScope.launch(Dispatchers.Main) {
        val min = dataPoints.minByOrNull { it.value }?.value ?: 0.0f

        val positiveDataPoints: List<DateDataPoint> = List(dataPoints.size) { i -> DateDataPoint(dataPoints[i].date, dataPoints[i].value - min) }

        data.clear()
        data.addAll(positiveDataPoints)

        computePoints()

        postInvalidate()
        println("MB: invalidate: ${data.size}")
    }

    private fun computePoints() {
        points.clear()

        val graphHeight = height.toFloat()

        val maxValue: Float = data.maxByOrNull { it.value }!!.value

        val xStep: Float = width.toFloat() / (data.size - 1)

        for (i in 0 until data.size) {
            val xVal = xStep * i
            val yVal = graphHeight - data[i].value / maxValue * graphHeight

            points.add(PointF(xVal, yVal))
        }
    }

    private fun computePath() {
        if (points.isEmpty()) return

        with(path) {
            reset()

            moveTo(points.first().x, points.first().y)

            for (i in 0 until points.size) {
                lineTo(points[i].x, points[i].y)
            }
        }
    }

    //endregion

    companion object {

    }
}

這是 output：

2021-02-19 18:13:25.210 29400-29400/at.guger.moneybook.dev I/System.out: MB: invalidate: 28
2021-02-19 18:13:30.146 29400-29400/at.guger.moneybook.dev I/System.out: MB: onSizeChanged: 0
2021-02-19 18:13:30.153 29400-29400/at.guger.moneybook.dev I/System.out: MB: invalidate: 28
2021-02-19 18:13:32.424 29400-29400/at.guger.moneybook.dev I/System.out: MB: onSizeChanged: 0
2021-02-19 18:13:32.429 29400-29400/at.guger.moneybook.dev I/System.out: MB: invalidate: 28
2021-02-19 18:13:34.897 29400-29400/at.guger.moneybook.dev I/System.out: MB: onSizeChanged: 0
2021-02-19 18:13:34.900 29400-29400/at.guger.moneybook.dev I/System.out: MB: invalidate: 28
2021-02-19 18:13:37.077 29400-29400/at.guger.moneybook.dev I/System.out: MB: onSizeChanged: 0
2021-02-19 18:13:37.083 29400-29400/at.guger.moneybook.dev I/System.out: MB: invalidate: 28
2021-02-19 18:13:38.689 29400-29400/at.guger.moneybook.dev I/System.out: MB: invalidate: 28  <---- this is the case when it doesn't draw
2021-02-19 18:13:38.697 29400-29400/at.guger.moneybook.dev I/System.out: MB: onSizeChanged: 28 <---- doesn't draw

我已經嘗試在onSizeChanged()中調用invalidate() ) ，設置setWillNotDraw(false)或使用postInvalidateDelayed(100)延遲調用invalidate() ) 。

Answer 1

我找到了解決該問題的方法：

要檢查是否已調用onSizeChanged ，我在方法setDataPoints中檢查height * width > 0 。

如果這個條件不成立，我設置一個標志來重新計算尺寸變化的繪圖數據。

在onSizeChanged中，我檢查該標志並再次調用我的setDataPoints方法，這現在可以工作了。