我已经使用了相同的代码块，已经在接受的答案，但它不会像在android 9一样工作，所以更新措施根据这一点

v.measure(MeasureSpec.makeMeasureSpec(parentView.getWidth(), MeasureSpec.EXACTLY), MeasureSpec.makeMeasureSpec(parentView.getWidth(), MeasureSpec.AT_MOST));

约束的工作方式在android 9中有所不同。

利用Kotlin扩展函数这是测试和最短的答案

在任何视图上调用animateVisibility(expand/collapse)即可。

fun View.animateVisibility(setVisible: Boolean) {
    if (setVisible) expand(this) else collapse(this)
}

private fun expand(view: View) {
    view.measure(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT)
    val initialHeight = 0
    val targetHeight = view.measuredHeight

    // Older versions of Android (pre API 21) cancel animations for views with a height of 0.
    //v.getLayoutParams().height = 1;
    view.layoutParams.height = 0
    view.visibility = View.VISIBLE

    animateView(view, initialHeight, targetHeight)
}

private fun collapse(view: View) {
    val initialHeight = view.measuredHeight
    val targetHeight = 0

    animateView(view, initialHeight, targetHeight)
}

private fun animateView(v: View, initialHeight: Int, targetHeight: Int) {
    val valueAnimator = ValueAnimator.ofInt(initialHeight, targetHeight)
    valueAnimator.addUpdateListener { animation ->
        v.layoutParams.height = animation.animatedValue as Int
        v.requestLayout()
    }
    valueAnimator.addListener(object : Animator.AnimatorListener {
        override fun onAnimationEnd(animation: Animator) {
            v.layoutParams.height = targetHeight
        }

        override fun onAnimationStart(animation: Animator) {}
        override fun onAnimationCancel(animation: Animator) {}
        override fun onAnimationRepeat(animation: Animator) {}
    })
    valueAnimator.duration = 300
    valueAnimator.interpolator = DecelerateInterpolator()
    valueAnimator.start()
}

你的思路是对的。确保在动画开始之前将v1设置为布局高度为0。在开始动画之前，您需要初始化您的设置，使其看起来像动画的第一帧。

根据@Tom Esterez和@Seth Nelson的解决方案，我对它们进行了简化。与原始解决方案一样，它不依赖于开发人员选项(动画设置)。

private void resizeWithAnimation(final View view, int duration, final int targetHeight) {
    final int initialHeight = view.getMeasuredHeight();
    final int distance = targetHeight - initialHeight;

    view.setVisibility(View.VISIBLE);

    Animation a = new Animation() {
        @Override
        protected void applyTransformation(float interpolatedTime, Transformation t) {
            if (interpolatedTime == 1 && targetHeight == 0) {
                view.setVisibility(View.GONE);
            }
            view.getLayoutParams().height = (int) (initialHeight + distance * interpolatedTime);
            view.requestLayout();
        }

        @Override
        public boolean willChangeBounds() {
            return true;
        }
    };

    a.setDuration(duration);
    view.startAnimation(a);
}

好吧，我刚刚发现了一个非常丑陋的解决方案:

public static Animation expand(final View v, Runnable onEnd) {
    try {
        Method m = v.getClass().getDeclaredMethod("onMeasure", int.class, int.class);
        m.setAccessible(true);
        m.invoke(
            v,
            MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED),
            MeasureSpec.makeMeasureSpec(((View)v.getParent()).getMeasuredHeight(), MeasureSpec.AT_MOST)
        );
    } catch (Exception e){
        Log.e("test", "", e);
    }
    final int initialHeight = v.getMeasuredHeight();
    Log.d("test", "initialHeight="+initialHeight);

    v.getLayoutParams().height = 0;
    v.setVisibility(View.VISIBLE);
    Animation a = new Animation()
    {
        @Override
        protected void applyTransformation(float interpolatedTime, Transformation t) {
            final int newHeight = (int)(initialHeight * interpolatedTime);
            v.getLayoutParams().height = newHeight;
            v.requestLayout();
        }

        @Override
        public boolean willChangeBounds() {
            return true;
        }
    };
    a.setDuration(5000);
    v.startAnimation(a);
    return a;
}

请随意提出一个更好的解决方案!

@Tom Esterez的回答，但更新为正确使用view.measure()每个Android getMeasuredHeight返回错误的值!

    // http://easings.net/
    Interpolator easeInOutQuart = PathInterpolatorCompat.create(0.77f, 0f, 0.175f, 1f);

    public static Animation expand(final View view) {
        int matchParentMeasureSpec = View.MeasureSpec.makeMeasureSpec(((View) view.getParent()).getWidth(), View.MeasureSpec.EXACTLY);
        int wrapContentMeasureSpec = View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED);
        view.measure(matchParentMeasureSpec, wrapContentMeasureSpec);
        final int targetHeight = view.getMeasuredHeight();

        // Older versions of android (pre API 21) cancel animations for views with a height of 0 so use 1 instead.
        view.getLayoutParams().height = 1;
        view.setVisibility(View.VISIBLE);

        Animation animation = new Animation() {
        @Override
        protected void applyTransformation(float interpolatedTime, Transformation t) {

               view.getLayoutParams().height = interpolatedTime == 1
                    ? ViewGroup.LayoutParams.WRAP_CONTENT
                    : (int) (targetHeight * interpolatedTime);

            view.requestLayout();
        }

            @Override
            public boolean willChangeBounds() {
                return true;
            }
        };

        animation.setInterpolator(easeInOutQuart);
        animation.setDuration(computeDurationFromHeight(view));
        view.startAnimation(animation);

        return animation;
    }

    public static Animation collapse(final View view) {
        final int initialHeight = view.getMeasuredHeight();

        Animation a = new Animation() {
            @Override
            protected void applyTransformation(float interpolatedTime, Transformation t) {
                if (interpolatedTime == 1) {
                    view.setVisibility(View.GONE);
                } else {
                    view.getLayoutParams().height = initialHeight - (int) (initialHeight * interpolatedTime);
                    view.requestLayout();
                }
            }

            @Override
            public boolean willChangeBounds() {
                return true;
            }
        };

        a.setInterpolator(easeInOutQuart);

        int durationMillis = computeDurationFromHeight(view);
        a.setDuration(durationMillis);

        view.startAnimation(a);

        return a;
    }

    private static int computeDurationFromHeight(View view) {
        // 1dp/ms * multiplier
        return (int) (view.getMeasuredHeight() / view.getContext().getResources().getDisplayMetrics().density);
    }