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

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。

其他回答

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);

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!

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);

这是我的解决方案。我认为这样更简单。它只是扩展了视图,但很容易扩展。

public class WidthExpandAnimation extends Animation
{
    int _targetWidth;
    View _view;

    public WidthExpandAnimation(View view)
    {
        _view = view;
    }

    @Override
    protected void applyTransformation(float interpolatedTime, Transformation t)
    {
        if (interpolatedTime < 1.f)
        {
            int newWidth = (int) (_targetWidth * interpolatedTime);

            _view.layout(_view.getLeft(), _view.getTop(),
                    _view.getLeft() + newWidth, _view.getBottom());
        }
        else
            _view.requestLayout();
    }

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

        _targetWidth = width;
    }

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

我已经使用了相同的代码块,已经在接受的答案,但它不会像在android 9一样工作,所以更新措施根据这一点

v.measure(MeasureSpec.makeMeasureSpec(parentView.getWidth(), MeasureSpec.EXACTLY), MeasureSpec.makeMeasureSpec(parentView.getWidth(), MeasureSpec.AT_MOST));

约束的工作方式在android 9中有所不同。