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

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;
    }
}

其他回答

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

另一种选择是使用以下缩放因子的缩放动画进行扩展:

ScaleAnimation anim = new ScaleAnimation(1, 1, 0, 1);

至于坍塌:

ScaleAnimation anim = new ScaleAnimation(1, 1, 1, 0);

你可以稍微改变一下使用ViewPropertyAnimator。若要折叠,请将视图缩放到1像素的高度,然后隐藏它。展开,显示它,然后展开到它的高度。

private void collapse(final View view) {
    view.setPivotY(0);
    view.animate().scaleY(1/view.getHeight()).setDuration(1000).withEndAction(new Runnable() {
        @Override public void run() {
            view.setVisibility(GONE);
        }
    });
}

private void expand(View view, int height) {
    float scaleFactor = height / view.getHeight();

    view.setVisibility(VISIBLE);
    view.setPivotY(0);
    view.animate().scaleY(scaleFactor).setDuration(1000);
}

枢轴告诉视图从哪里开始缩放,默认是在中间。持续时间是可选的(默认= 1000)。你也可以设置插值器来使用,比如.setInterpolator(new accelerateeraderateinterpolator ())

我改编了汤姆·埃斯特兹(Tom Esterez)目前接受的答案,这个答案有效,但动画起伏不定,不太流畅。我的解决方案基本上是用ValueAnimator替换动画,它可以与你选择的Interpolator相匹配,以实现各种效果,如超调、反弹、加速等。

这个解决方案非常适用于具有动态高度的视图(即使用WRAP_CONTENT),因为它首先测量实际所需的高度,然后动画到该高度。

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

    ValueAnimator va = ValueAnimator.ofInt(1, targetHeight);
    va.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
        public void onAnimationUpdate(ValueAnimator animation) {
            v.getLayoutParams().height = (Integer) animation.getAnimatedValue();
            v.requestLayout();
        }
    });
    va.addListener(new Animator.AnimatorListener() {
        @Override
        public void onAnimationEnd(Animator animation) {
            v.getLayoutParams().height = ViewGroup.LayoutParams.WRAP_CONTENT;
        }

        @Override public void onAnimationStart(Animator animation) {}
        @Override public void onAnimationCancel(Animator animation) {}
        @Override public void onAnimationRepeat(Animator animation) {}
    });
    va.setDuration(300);
    va.setInterpolator(new OvershootInterpolator());
    va.start();
}

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

    ValueAnimator va = ValueAnimator.ofInt(initialHeight, 0);
    va.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
        public void onAnimationUpdate(ValueAnimator animation) {
            v.getLayoutParams().height = (Integer) animation.getAnimatedValue();
            v.requestLayout();
        }
    });
    va.addListener(new Animator.AnimatorListener() {
        @Override
        public void onAnimationEnd(Animator animation) {
            v.setVisibility(View.GONE);
        }

        @Override public void onAnimationStart(Animator animation) {}
        @Override public void onAnimationCancel(Animator animation) {}
        @Override public void onAnimationRepeat(Animator animation) {}
    });
    va.setDuration(300);
    va.setInterpolator(new DecelerateInterpolator());
    va.start();
}

然后你只需调用expand(myView);或崩溃(myView);。

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。