我创建的版本中，你不需要指定布局高度，因此它更容易和更干净的使用。解决方案是在动画的第一帧中获取高度(至少在我的测试中是可用的)。通过这种方式，您可以为视图提供任意高度和底边距。

在构造函数中还有一个小hack -底部边距被设置为-10000，以便视图在转换之前保持隐藏(防止闪烁)。

public class ExpandAnimation extends Animation {


    private View mAnimatedView;
    private ViewGroup.MarginLayoutParams mViewLayoutParams;
    private int mMarginStart, mMarginEnd;

    public ExpandAnimation(View view) {
        mAnimatedView = view;
        mViewLayoutParams = (ViewGroup.MarginLayoutParams) view.getLayoutParams();
        mMarginEnd = mViewLayoutParams.bottomMargin;
        mMarginStart = -10000; //hide before viewing by settings very high negative bottom margin (hack, but works nicely)
        mViewLayoutParams.bottomMargin = mMarginStart;
        mAnimatedView.setLayoutParams(mViewLayoutParams);
    }

    @Override
    protected void applyTransformation(float interpolatedTime, Transformation t) {
        super.applyTransformation(interpolatedTime, t);
            //view height is already known when the animation starts
            if(interpolatedTime==0){
                mMarginStart = -mAnimatedView.getHeight();
            }
            mViewLayoutParams.bottomMargin = (int)((mMarginEnd-mMarginStart) * interpolatedTime)+mMarginStart;
            mAnimatedView.setLayoutParams(mViewLayoutParams);
    }
}

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!

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);

如果你不想扩展或折叠所有的方式-这里是一个简单的HeightAnimation -

import android.view.View;
import android.view.animation.Animation;
import android.view.animation.Transformation;

public class HeightAnimation extends Animation {
    protected final int originalHeight;
    protected final View view;
    protected float perValue;

    public HeightAnimation(View view, int fromHeight, int toHeight) {
        this.view = view;
        this.originalHeight = fromHeight;
        this.perValue = (toHeight - fromHeight);
    }

    @Override
    protected void applyTransformation(float interpolatedTime, Transformation t) {
        view.getLayoutParams().height = (int) (originalHeight + perValue * interpolatedTime);
        view.requestLayout();
    }

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

用法:

HeightAnimation heightAnim = new HeightAnimation(view, view.getHeight(), viewPager.getHeight() - otherView.getHeight());
heightAnim.setDuration(1000);
view.startAnimation(heightAnim);

展开/折叠视图的最佳解决方案:

    @Override
    public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
        View view = buttonView.getId() == R.id.tb_search ? fSearch : layoutSettings;
        transform(view, 200, isChecked
            ? ViewGroup.LayoutParams.WRAP_CONTENT
            : 0);
    }

    public static void transform(final View v, int duration, int targetHeight) {
        int prevHeight  = v.getHeight();
        v.setVisibility(View.VISIBLE);
        ValueAnimator animator;
        if (targetHeight == ViewGroup.LayoutParams.WRAP_CONTENT) {
            v.measure(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
            animator = ValueAnimator.ofInt(prevHeight, v.getMeasuredHeight());
        } else {
            animator = ValueAnimator.ofInt(prevHeight, targetHeight);
        }
        animator.addUpdateListener(animation -> {
            v.getLayoutParams().height = (animation.getAnimatedFraction() == 1.0f)
                    ? targetHeight
                    : (int) animation.getAnimatedValue();
            v.requestLayout();
        });
        animator.setInterpolator(new LinearInterpolator());
        animator.setDuration(duration);
        animator.start();
    }

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;
    }
}