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;
    }
}

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()
}

/**
 * Animation that either expands or collapses a view by sliding it down to make
 * it visible. Or by sliding it up so it will hide. It will look like it slides
 * behind the view above.
 * 
 */
public class FinalExpandCollapseAnimation extends Animation
{
    private View mAnimatedView;
    private int mEndHeight;
    private int mType;
    public final static int COLLAPSE = 1;
    public final static int EXPAND = 0;
    private LinearLayout.LayoutParams mLayoutParams;
    private RelativeLayout.LayoutParams mLayoutParamsRel;
    private String layout;
    private Context context;

    /**
     * Initializes expand collapse animation, has two types, collapse (1) and
     * expand (0).
     * 
     * @param view
     *            The view to animate
     * @param type
     *            The type of animation: 0 will expand from gone and 0 size to
     *            visible and layout size defined in xml. 1 will collapse view
     *            and set to gone
     */
    public FinalExpandCollapseAnimation(View view, int type, int height, String layout, Context context)
    {
        this.layout = layout;
        this.context = context;
        mAnimatedView = view;
        mEndHeight = mAnimatedView.getMeasuredHeight();
        if (layout.equalsIgnoreCase("linear"))
            mLayoutParams = ((LinearLayout.LayoutParams) view.getLayoutParams());
        else
            mLayoutParamsRel = ((RelativeLayout.LayoutParams) view.getLayoutParams());
        mType = type;
        if (mType == EXPAND)
        {
            AppConstant.ANIMATED_VIEW_HEIGHT = height;
        }
        else
        {
            if (layout.equalsIgnoreCase("linear"))
                mLayoutParams.topMargin = 0;
            else
                mLayoutParamsRel.topMargin = convertPixelsIntoDensityPixels(36);
        }
        setDuration(600);
    }

    @Override
    protected void applyTransformation(float interpolatedTime, Transformation t)
    {
        super.applyTransformation(interpolatedTime, t);
        if (interpolatedTime < 1.0f)
        {
            if (mType == EXPAND)
            {
                if (layout.equalsIgnoreCase("linear"))
                {
                    mLayoutParams.height = AppConstant.ANIMATED_VIEW_HEIGHT
                            + (-AppConstant.ANIMATED_VIEW_HEIGHT + (int) (AppConstant.ANIMATED_VIEW_HEIGHT * interpolatedTime));
                }
                else
                {
                    mLayoutParamsRel.height = AppConstant.ANIMATED_VIEW_HEIGHT
                            + (-AppConstant.ANIMATED_VIEW_HEIGHT + (int) (AppConstant.ANIMATED_VIEW_HEIGHT * interpolatedTime));
                }
                mAnimatedView.setVisibility(View.VISIBLE);
            }
            else
            {
                if (layout.equalsIgnoreCase("linear"))
                    mLayoutParams.height = mEndHeight - (int) (mEndHeight * interpolatedTime);
                else
                    mLayoutParamsRel.height = mEndHeight - (int) (mEndHeight * interpolatedTime);
            }
            mAnimatedView.requestLayout();
        }
        else
        {
            if (mType == EXPAND)
            {
                if (layout.equalsIgnoreCase("linear"))
                {
                    mLayoutParams.height = AppConstant.ANIMATED_VIEW_HEIGHT;
                    mLayoutParams.topMargin = 0;
                }
                else
                {
                    mLayoutParamsRel.height = AppConstant.ANIMATED_VIEW_HEIGHT;
                    mLayoutParamsRel.topMargin = convertPixelsIntoDensityPixels(36);
                }
                mAnimatedView.setVisibility(View.VISIBLE);
                mAnimatedView.requestLayout();
            }
            else
            {
                if (layout.equalsIgnoreCase("linear"))
                    mLayoutParams.height = 0;
                else
                    mLayoutParamsRel.height = 0;
                mAnimatedView.setVisibility(View.GONE);
                mAnimatedView.requestLayout();
            }
        }
    }

    private int convertPixelsIntoDensityPixels(int pixels)
    {
        DisplayMetrics metrics = context.getResources().getDisplayMetrics();
        return (int) metrics.density * pixels;
    }
}

该类可以通过以下方式调用

   if (findViewById(R.id.ll_specailoffer_show_hide).getVisibility() == View.VISIBLE) {
                        ((ImageView) findViewById(R.id.iv_specialhour_seemore)).setImageResource(R.drawable.white_dropdown_up);

                        FinalExpandCollapseAnimation finalExpandCollapseAnimation = new FinalExpandCollapseAnimation(
                                findViewById(R.id.ll_specailoffer_show_hide),
                                FinalExpandCollapseAnimation.COLLAPSE,
                                SpecialOfferHeight, "linear", this);
                        findViewById(R.id.ll_specailoffer_show_hide)
                                .startAnimation(finalExpandCollapseAnimation);
                        ((View) findViewById(R.id.ll_specailoffer_show_hide).getParent()).invalidate();
                    } else {
                        ((ImageView) findViewById(R.id.iv_specialhour_seemore)).setImageResource(R.drawable.white_dropdown);

                        FinalExpandCollapseAnimation finalExpandCollapseAnimation = new FinalExpandCollapseAnimation(
                                findViewById(R.id.ll_specailoffer_show_hide),
                                FinalExpandCollapseAnimation.EXPAND,
                                SpecialOfferHeight, "linear", this);
                        findViewById(R.id.ll_specailoffer_show_hide)
                                .startAnimation(finalExpandCollapseAnimation);
                        ((View) findViewById(R.id.ll_specailoffer_show_hide).getParent()).invalidate();
                    }

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!

这是一个片段，我用来调整一个视图(线性布局)的宽度与动画。

代码应该根据目标大小进行扩展或收缩。如果你想要一个fill_parent宽度，你必须在将标志设置为true时将父类. getmeasuredwidth作为目标宽度。

希望它能帮助到你们中的一些人。

public class WidthResizeAnimation extends Animation {
int targetWidth;
int originaltWidth;
View view;
boolean expand;
int newWidth = 0;
boolean fillParent;

public WidthResizeAnimation(View view, int targetWidth, boolean fillParent) {
    this.view = view;
    this.originaltWidth = this.view.getMeasuredWidth();
    this.targetWidth = targetWidth;
    newWidth = originaltWidth;
    if (originaltWidth > targetWidth) {
        expand = false;
    } else {
        expand = true;
    }
    this.fillParent = fillParent;
}

@Override
protected void applyTransformation(float interpolatedTime, Transformation t) {
    if (expand && newWidth < targetWidth) {
        newWidth = (int) (newWidth + (targetWidth - newWidth) * interpolatedTime);
    }

    if (!expand && newWidth > targetWidth) {
        newWidth = (int) (newWidth - (newWidth - targetWidth) * interpolatedTime);
    }
    if (fillParent && interpolatedTime == 1.0) {
        view.getLayoutParams().width = -1;

    } else {
        view.getLayoutParams().width = newWidth;
    }
    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;
}

}

我采用了@LenaYan的解决方案，但它并没有正常工作 对我来说(因为它在折叠和/或扩展之前将视图转换为0高度视图)并做了一些更改。

现在它工作得很好，通过获取视图之前的高度并开始扩展这个大小。坍缩也是一样的。

你可以简单地复制和粘贴下面的代码:

public static void expand(final View v, int duration, int targetHeight) {

    int prevHeight  = v.getHeight();

    v.setVisibility(View.VISIBLE);
    ValueAnimator valueAnimator = ValueAnimator.ofInt(prevHeight, 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(duration);
    valueAnimator.start();
}

public static void collapse(final View v, int duration, int targetHeight) {
    int prevHeight  = v.getHeight();
    ValueAnimator valueAnimator = ValueAnimator.ofInt(prevHeight, targetHeight);
    valueAnimator.setInterpolator(new DecelerateInterpolator());
    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(duration);
    valueAnimator.start();
}

用法:

//Expanding the View
   expand(yourView, 2000, 200);

// Collapsing the View     
   collapse(yourView, 2000, 100);

很容易!

感谢LenaYan提供的初始代码!