调试Android ValueAnimator

Question

我一直在尝试使用Kotlin扩展功能和CardView为我的ValueAnimator创建收起/展开动画。这是动画的代码（CardView扩展功能）：

fun CardView.collapse() {
    val content = findViewById<RecyclerView>(R.id.rv_content)
    val arrow = findViewById<ImageView>(R.id.contents_arrow)
    val currentHeight = content.layoutParams.height

    val rvAnimator = ValueAnimator.ofInt(currentHeight, 0).apply {
        addUpdateListener{ updatedAnimation ->
            val params = content.layoutParams
            params.height = updatedAnimation.animatedValue as Int
            content.layoutParams = params
        }
        duration = 1000
    }

    val arrowAnimator = ValueAnimator.ofFloat(00f, 180f).apply {
        addUpdateListener { updatedAnimation ->
            arrow.rotation = updatedAnimation.animatedValue as Float
        }

        duration = 1000
        startDelay = 250
    }

    AnimatorSet().apply {
        playTogether(rvAnimator, arrowAnimator)
        start()
    }

}

fun CardView.expand(maxHeight: Int) {
    val content = findViewById<RecyclerView>(R.id.rv_content)
    val arrow = findViewById<ImageView>(R.id.contents_arrow)

    val rvAnimator = ValueAnimator.ofInt(0, maxHeight).apply {
        addUpdateListener{updatedAnimation ->
            val params = content.layoutParams
            params.height = updatedAnimation.animatedValue as Int
            content.layoutParams = params
        }
        duration = 1000
    }

    val arrowAnimator = ValueAnimator.ofFloat(180f, 0f).apply {
        addUpdateListener { updatedAnimation ->
            arrow.rotation = updatedAnimation.animatedValue as Float
        }

        duration = 1000
        startDelay = 250
    }

    AnimatorSet().apply {
        playTogether(rvAnimator, arrowAnimator)
        start()
    }

}

fun CardView.isCollapsed(): Boolean {
    val content = findViewById<RecyclerView>(R.id.rv_content)
    return content.layoutParams.height == 0

}

然后单击以启动动画：

override fun onBindViewHolder(holder: SectionViewHolder, position: Int) {

    holder.itemView.setOnClickListener {
        if ((it as CardView).isCollapsed()) {
            it.expand(holder.maxHeight)
        } else {
            it.collapse()
        }
    }
}

但是，我的动画似乎引起了一些非常奇怪的绘图问题。第一次单击CardView时会有一些延迟。不过，更令人担忧的是，CardView总是在动画结束后又回到展开状态：

当箭头指向上方时，CardView应该合拢，反之亦然。

任何人都可以就如何解决此问题提供任何意见吗？调试动画时，我什至不知道从哪里开始。任何输入表示赞赏：）

Answer 1

您不需要创建折叠动画。

您可以简单地反转创建的动画以进行扩展，例如：

rvAnimator.reverse()
arrowAnimator.reverse()

为此，您不能使用AnimatorSet，您必须像这样自己启动两个动画：

rvAnimator.start()
arrowAnimator.start()