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

下面是两个简单的kotlin扩展函数概述。

fun View.expand() {
    visibility = View.VISIBLE
    val animate = TranslateAnimation(0f, 0f, -height.toFloat(), 0f)
    animate.duration = 200
    animate.fillAfter = true
    startAnimation(animate)
}

fun View.collapse() {
    val animate = TranslateAnimation(0f, 0f, 0f, -height.toFloat() )
    animate.duration = 200
    animate.fillAfter = true
    startAnimation(animate)
}

其他回答

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。

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

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()
}

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);

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();