油漆的颜色为什么不改变？

Question

我有一个简单的CustomView，它绘制了3个垂直圆：

SimpleDrawingView.kt

 class SimpleDrawingView @JvmOverloads constructor(
        context: Context,
        attrs: AttributeSet? = null,
        defStyle: Int = 0) : View(context, attrs, defStyle) {
    
        private val drawPaint: Paint = Paint()
    
        init {
            setupPaint()
        }
    
        private fun setupPaint() {
            drawPaint.color = Color.RED
            drawPaint.isAntiAlias = true
            drawPaint.strokeWidth = 5f
            drawPaint.style = Paint.Style.STROKE
            drawPaint.strokeJoin = Paint.Join.ROUND
            drawPaint.strokeCap = Paint.Cap.ROUND
        }

        override fun onDraw(canvas: Canvas?) {
            canvas?.drawCircle(50f, 50f, 40f, drawPaint)
            drawPaint.color = Color.BLUE
            canvas?.drawCircle(50f, 150f, 40f, drawPaint)
            drawPaint.color = Color.GREEN
            canvas?.drawCircle(50f, 250f, 40f, drawPaint)
        }
    }

我将初始颜色设置为红色，然后使用onDraw()方法更改颜色。但是它工作不正确，而是先绘制绿色圆圈而不是红色，为什么？

Answer 1

这是自定义视图上使用@JvmOverloads的问题。请按如下所示更改您的代码：

class SimpleDrawingView  : View {

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

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

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

    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
    constructor(context: Context?, attrs: AttributeSet?, defStyleAttr: Int, defStyleRes: Int) : super(
        context, attrs, defStyleAttr, defStyleRes
    ) {
    }

    private val drawPaint: Paint = Paint()

    init {
        setupPaint()
    }

    private fun setupPaint() {
        drawPaint.color = Color.RED
        drawPaint.isAntiAlias = true
        drawPaint.strokeWidth = 5f
        drawPaint.style = Paint.Style.STROKE
        drawPaint.strokeJoin = Paint.Join.ROUND
        drawPaint.strokeCap = Paint.Cap.ROUND
    }

    override fun onDraw(canvas: Canvas?) {
        canvas?.drawCircle(50f, 50f, 40f, drawPaint)
        drawPaint.color = Color.BLUE
        canvas?.drawCircle(50f, 150f, 40f, drawPaint)
        drawPaint.color = Color.GREEN
        canvas?.drawCircle(50f, 250f, 40f, drawPaint)
    }
}

输出如下：