安卓：展开/​​折叠动画 [英] Android: Expand/collapse animation

问题描述

比方说，我有一个垂直的LinearLayout：

Let's say I have a vertical linearLayout with :

[v1]
[v2]

在默认情况下V1已经visibily = GONE。我想显示V1与拓展动画，并推低V2在同一时间。

By default v1 has visibily = GONE. I would like to show v1 with an expand animation and push down v2 at the same time.

我想是这样的：

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;
    }
};

但有了这个解决方案，我有一个闪烁的动画开始的时候。我认为这是造成V1显示全尺寸的动画应用之前。

But with this solution, I have a blink when the animation starts. I think it's caused by v1 displaying full size before the animation is applied.

使用JavaScript，这是一条线的jQuery！任何简单的方法来与Android做到这一点？

With javascript, this is one line of jQuery! Any simple way to do this with android?

推荐答案

我看到，这个问题变得受欢迎，所以我发表我的实际解决方案。其主要优点是，你不需要知道扩展高度运用动画，一旦视图扩展，它可以适应高度，如果内容的修改。这对我的伟大工程。

I see that this question became popular so I post my actual solution. The main advantage is that you don't have to know the expanded height to apply the animation and once the view is expanded, it adapts height if content changes. It works great for me.

public static void expand(final View v) {
    v.measure(LayoutParams.MATCH_PARENT, 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);
    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;
        }
    };

    // 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;
        }
    };

    // 1dp/ms
    a.setDuration((int)(initialHeight / v.getContext().getResources().getDisplayMetrics().density));
    v.startAnimation(a);
}

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