如何修复 android.widget.TextView() 需要 api 21 错误 [英] How to fix android.widget.TextView() requires api 21 error

问题描述

我有 BubbleTextView，它是一个自定义 TextView，后面有一个蓝色气泡作为背景.

I have BubbleTextView which is a custom TextView with a blue bubble behind as background.

这是我的代码:

class BubbleTextView(context: Context?, attrs: AttributeSet?, defStyleAttr: Int, defStyleRes: Int) : TextView(context, attrs, defStyleAttr, defStyleRes) {

    private val paint = Paint(Paint.ANTI_ALIAS_FLAG)
    private val rectPath = Path()
    private val trianglePath = Path()

    private val rectF = RectF()
    private val triangleSize = resources.getDimensionPixelSize(R.dimen.triangle_size_20dp).toFloat()
    private val cornerRadius = resources.getDimensionPixelSize(R.dimen.corner_radius_4dp).toFloat()

    constructor(context: Context?):this(context, null, 0, 0)
    constructor(context: Context?, attrs: AttributeSet?):this(context, attrs, 0, 0)
    constructor(context: Context?, attrs: AttributeSet?, defStyleAttr: Int):this(context, attrs, defStyleAttr, 0)

    init{
        paint.style = Paint.Style.FILL
        paint.color = Color.CYAN
    }

    override fun onLayout(changed: Boolean, left: Int, top: Int, right: Int, bottom: Int) {
        super.onLayout(changed, left, top, right, bottom)
        val myWidth = (right - left).toFloat()
        val myHeight = (bottom - top).toFloat()
        val centerX = myWidth / 2f
        val lowerEdgeY = myHeight * 0.8f

        rectF.set(0f, 0f, myWidth, lowerEdgeY)
        rectPath.addRoundRect(rectF,cornerRadius, cornerRadius, Path.Direction.CW )

        val delta = triangleSize * 0.5f
        trianglePath.moveTo(centerX - delta, lowerEdgeY)
        trianglePath.lineTo(centerX + delta, lowerEdgeY)
        trianglePath.lineTo(centerX, myHeight)
        trianglePath.close()
    }

    override fun onDraw(canvas: Canvas?) {
        canvas?.drawPath(rectPath, paint)
        canvas?.drawPath(trianglePath, paint)
        super.onDraw(canvas)
    }
}

: TextView 以红色高亮显示错误:android.widget.TextView() 需要 api 21.

: TextView is highlighted red with error: android.widget.TextView() requires api 21.

对于 api 21 及以上版本，apl 工作正常.但是对于下面的应用程序立即崩溃了.

For api 21 and above the apl is working fine. But for below the app crashed instantly.

提前致谢.

推荐答案

Constructorclass BubbleTextView(context: Context?, attrs: AttributeSet?, defStyleAttr: Int, defStyleRes: Int) : TextView(context, attrs, defStyleAttr, defStyleRes)在 API 级别 21 中添加，因此您只能使用 >= 21

Constructor class BubbleTextView(context: Context?, attrs: AttributeSet?, defStyleAttr: Int, defStyleRes: Int) : TextView(context, attrs, defStyleAttr, defStyleRes) added in API level 21, so you only can use >= 21

你应该:

class BubbleTextView : TextView {

    private val paint = Paint(Paint.ANTI_ALIAS_FLAG)
    private val rectPath = Path()
    private val trianglePath = Path()

    private val rectF = RectF()
    private val triangleSize = resources.getDimensionPixelSize(R.dimen.triangle_size_20dp).toFloat()
    private val cornerRadius = resources.getDimensionPixelSize(R.dimen.corner_radius_4dp).toFloat()

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

    init{
        paint.style = Paint.Style.FILL
        paint.color = Color.CYAN
    }

    override fun onLayout(changed: Boolean, left: Int, top: Int, right: Int, bottom: Int) {
        super.onLayout(changed, left, top, right, bottom)
        val myWidth = (right - left).toFloat()
        val myHeight = (bottom - top).toFloat()
        val centerX = myWidth / 2f
        val lowerEdgeY = myHeight * 0.8f

        rectF.set(0f, 0f, myWidth, lowerEdgeY)
        rectPath.addRoundRect(rectF,cornerRadius, cornerRadius, Path.Direction.CW )

        val delta = triangleSize * 0.5f
        trianglePath.moveTo(centerX - delta, lowerEdgeY)
        trianglePath.lineTo(centerX + delta, lowerEdgeY)
        trianglePath.lineTo(centerX, myHeight)
        trianglePath.close()
    }

    override fun onDraw(canvas: Canvas?) {
        canvas?.drawPath(rectPath, paint)
        canvas?.drawPath(trianglePath, paint)
        super.onDraw(canvas)
    }
}

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