假设我有一个垂直线性布局:

[v1]
[v2]

默认情况下,v1已经可见= GONE。我想用一个展开动画显示v1,同时下推v2。

我是这样做的:

Animation a = new Animation()
{
    int initialHeight;

    @Override
    protected void applyTransformation(float interpolatedTime, Transformation t) {
        final int newHeight = (int)(initialHeight * interpolatedTime);
        v.getLayoutParams().height = newHeight;
        v.requestLayout();
    }

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

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

但是用这个解决方案,当动画开始时我有一个眨眼。我认为这是由于v1在应用动画之前显示全尺寸。

用javascript,这是一行jQuery!android有什么简单的方法吗?


当前回答

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()
}

其他回答

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;
    }
}

我看到这个问题很受欢迎,所以我发布了我的实际解决方案。主要的优点是你不需要知道扩展的高度来应用动画,一旦视图被扩展,它会在内容改变时适应高度。这对我来说很有效。

public static void expand(final View v) {
    int matchParentMeasureSpec = View.MeasureSpec.makeMeasureSpec(((View) v.getParent()).getWidth(), View.MeasureSpec.EXACTLY);
    int wrapContentMeasureSpec = View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED);
    v.measure(matchParentMeasureSpec, wrapContentMeasureSpec);
    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);
    Animation a = new Animation()
    {
        @Override
        protected void applyTransformation(float interpolatedTime, Transformation t) {
            v.getLayoutParams().height = interpolatedTime == 1
                    ? LayoutParams.WRAP_CONTENT
                    : (int)(targetHeight * interpolatedTime);
            v.requestLayout();
        }

        @Override
        public boolean willChangeBounds() {
            return true;
        }
    };
    
    // Expansion speed of 1dp/ms
    a.setDuration((int)(targetHeight / v.getContext().getResources().getDisplayMetrics().density));
    v.startAnimation(a);
}

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

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

        @Override
        public boolean willChangeBounds() {
            return true;
        }
    };
    
    // Collapse speed of 1dp/ms
    a.setDuration((int)(initialHeight / v.getContext().getResources().getDisplayMetrics().density));
    v.startAnimation(a);
}

正如@Jefferson在评论中提到的,你可以通过改变动画的持续时间(以及速度)来获得更流畅的动画。目前,它已设置为1dp/ms的速度

/**
 * 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();
                    }

使用ValueAnimator:

ValueAnimator expandAnimation = ValueAnimator.ofInt(mainView.getHeight(), 400);
expandAnimation.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
    @Override
    public void onAnimationUpdate(final ValueAnimator animation) {
        int height = (Integer) animation.getAnimatedValue();
        RelativeLayout.LayoutParams lp = (LayoutParams) mainView.getLayoutParams();
        lp.height = height;
    }
});


expandAnimation.setDuration(500);
expandAnimation.start();

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);
    }
}