android - Kotlin - 如何在函数内部执行函数？

Question

我有一个为动画创建的类，如下所示:

    class MyAnimations(val view: View) {

fun fadeAnimation() {
    val fadeAnimator = ValueAnimator.ofFloat(0.2f, 1f)

    fadeAnimator.addUpdateListener {
        val value = it.animatedValue as Float
        view.alpha = value
    }

    fadeAnimator.interpolator = DecelerateInterpolator(1.4f)
    fadeAnimator.duration = 400


    fun postAnimation() {

        fadeAnimator.addListener(object : Animator.AnimatorListener {
            override fun onAnimationRepeat(animation: Animator?) {
                //empty
            }

            override fun onAnimationEnd(animation: Animator?) {
                -- I WANT TO RUN CODE HERE --
            }

            override fun onAnimationCancel(animation: Animator?) {
                //empty
            }

            override fun onAnimationStart(animation: Animator?) {
                //empty
            }
        })
    }

    fadeAnimator.start()
    }
}

在我的 Activity 中，我的目标是在动画结束后执行类似这样的操作并运行 myfunction():

    MyAnimations(goPiano).fadeAnimation().postAnimation(myfunction())

或者像这样，并编写任何代码在我的动画结束时运行:

    MyAnimations(goPiano).fadeAnimation().postAnimation() {
            //Block of code here
        }

我需要在 MyAnimations 类中添加和更改什么才能执行此操作？我是 Kotlin 的新手，很想知道如何在我的类里面做到这一点。谢谢!

Answer 1

您可以使用高阶函数来做到这一点。你不需要函数内部的函数

fun fadeAnimation(postAnimCallback: () -> Unit) {
    val fadeAnimator = ValueAnimator.ofFloat(0.2f, 1f)

    fadeAnimator.addUpdateListener {
        val value = it.animatedValue as Float
        view.alpha = value
    }

    fadeAnimator.interpolator = DecelerateInterpolator(1.4f)
    fadeAnimator.duration = 400

    fadeAnimator.addListener(object : Animator.AnimatorListener {
        override fun onAnimationRepeat(animation: Animator?) {
            //empty
        }

        override fun onAnimationEnd(animation: Animator?) {
            postAnimCallback()
        }

        override fun onAnimationCancel(animation: Animator?) {
            //empty
        }

        override fun onAnimationStart(animation: Animator?) {
            //empty
        }
    })

    fadeAnimator.start()
}

现在你可以调用它了

MyAnimations(goPiano).fadeAnimation() {
     // post animation code
}

或

MyAnimations(goPiano).fadeAnimation(::postAnimation)

fun postAnimation() {
}