另一种选择是使用以下缩放因子的缩放动画进行扩展:

ScaleAnimation anim = new ScaleAnimation(1, 1, 0, 1);

至于坍塌:

ScaleAnimation anim = new ScaleAnimation(1, 1, 1, 0);

我试图做一个我认为非常相似的动画，并找到了一个优雅的解决方案。这段代码假设你总是从0->h或h->0 (h是最大高度)。三个构造函数参数是view =要动画的视图(在我的例子中是webview)， targetHeight =视图的最大高度，以及down =一个布尔值，用于指定方向(true =展开，false =折叠)。

public class DropDownAnim extends Animation {
    private final int targetHeight;
    private final View view;
    private final boolean down;

    public DropDownAnim(View view, int targetHeight, boolean down) {
        this.view = view;
        this.targetHeight = targetHeight;
        this.down = down;
    }

    @Override
    protected void applyTransformation(float interpolatedTime, Transformation t) {
        int newHeight;
        if (down) {
            newHeight = (int) (targetHeight * interpolatedTime);
        } else {
            newHeight = (int) (targetHeight * (1 - interpolatedTime));
        }
        view.getLayoutParams().height = newHeight;
        view.requestLayout();
    }

    @Override
    public void initialize(int width, int height, int parentWidth,
            int parentHeight) {
        super.initialize(width, height, parentWidth, parentHeight);
    }

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

是的，我同意上面的评论。事实上，它似乎是正确的(或者至少是最简单的?)事情要做的是指定(在XML中)一个初始布局高度“0px”——然后你可以传递另一个参数“toHeight”(即“最终高度”)到你的自定义动画子类的构造函数，例如，在上面的例子中，它看起来像这样:

    public DropDownAnim( View v, int toHeight ) { ... }

不管怎样，希望这能有所帮助!：）

我改编了汤姆·埃斯特兹(Tom Esterez)目前接受的答案，这个答案有效，但动画起伏不定，不太流畅。我的解决方案基本上是用ValueAnimator替换动画，它可以与你选择的Interpolator相匹配，以实现各种效果，如超调、反弹、加速等。

这个解决方案非常适用于具有动态高度的视图(即使用WRAP_CONTENT)，因为它首先测量实际所需的高度，然后动画到该高度。

public static void expand(final View v) {
    v.measure(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
    final int targetHeight = v.getMeasuredHeight();

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

    ValueAnimator va = ValueAnimator.ofInt(1, targetHeight);
    va.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
        public void onAnimationUpdate(ValueAnimator animation) {
            v.getLayoutParams().height = (Integer) animation.getAnimatedValue();
            v.requestLayout();
        }
    });
    va.addListener(new Animator.AnimatorListener() {
        @Override
        public void onAnimationEnd(Animator animation) {
            v.getLayoutParams().height = ViewGroup.LayoutParams.WRAP_CONTENT;
        }

        @Override public void onAnimationStart(Animator animation) {}
        @Override public void onAnimationCancel(Animator animation) {}
        @Override public void onAnimationRepeat(Animator animation) {}
    });
    va.setDuration(300);
    va.setInterpolator(new OvershootInterpolator());
    va.start();
}

public static void collapse(final View v) {
    final int initialHeight = v.getMeasuredHeight();

    ValueAnimator va = ValueAnimator.ofInt(initialHeight, 0);
    va.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
        public void onAnimationUpdate(ValueAnimator animation) {
            v.getLayoutParams().height = (Integer) animation.getAnimatedValue();
            v.requestLayout();
        }
    });
    va.addListener(new Animator.AnimatorListener() {
        @Override
        public void onAnimationEnd(Animator animation) {
            v.setVisibility(View.GONE);
        }

        @Override public void onAnimationStart(Animator animation) {}
        @Override public void onAnimationCancel(Animator animation) {}
        @Override public void onAnimationRepeat(Animator animation) {}
    });
    va.setDuration(300);
    va.setInterpolator(new DecelerateInterpolator());
    va.start();
}

然后你只需调用expand(myView);或崩溃(myView);。

来自@Tom Esterez和@Geraldo Neto的组合解决方案

public static void expandOrCollapseView(View v,boolean expand){

    if(expand){
        v.measure(ViewGroup.LayoutParams.MATCH_PARENT,ViewGroup.LayoutParams.WRAP_CONTENT);
        final int targetHeight = v.getMeasuredHeight();
        v.getLayoutParams().height = 0;
        v.setVisibility(View.VISIBLE);
        ValueAnimator valueAnimator = ValueAnimator.ofInt(targetHeight);
        valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator animation) {
                v.getLayoutParams().height = (int) animation.getAnimatedValue();
                v.requestLayout();
            }
        });
        valueAnimator.setInterpolator(new DecelerateInterpolator());
        valueAnimator.setDuration(500);
        valueAnimator.start();
    }
    else
    {
        final int initialHeight = v.getMeasuredHeight();
        ValueAnimator valueAnimator = ValueAnimator.ofInt(initialHeight,0);
        valueAnimator.setInterpolator(new DecelerateInterpolator());
        valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator animation) {
                v.getLayoutParams().height = (int) animation.getAnimatedValue();
                v.requestLayout();
                if((int)animation.getAnimatedValue() == 0)
                    v.setVisibility(View.GONE);
            }
        });
        valueAnimator.setInterpolator(new DecelerateInterpolator());
        valueAnimator.setDuration(500);
        valueAnimator.start();
    }
}

//sample usage
expandOrCollapseView((Your ViewGroup),(Your ViewGroup).getVisibility()!=View.VISIBLE);

public static void slide(View v, int speed, int pos) {
    v.animate().setDuration(speed);
    v.animate().translationY(pos);
    v.animate().start();
}

// slide down
slide(yourView, 250, yourViewHeight);
// slide up
slide(yourView, 250, 0);