android - 如何在 RecyclerView 项目出现时为其设置动画

Question

当 RecyclerView Items 出现时，我如何对其进行动画处理？

默认项目动画器仅在设置回收器数据后添加或删除数据时才动画。我是新开发的应用程序，不知道从哪里开始。

任何想法如何实现这一目标？

Answer 1

编辑:

根据the ItemAnimator documentation :

This class defines the animations that take place on items as changes are made to the adapter.

因此，除非您将项目一一添加到 RecyclerView 并在每次迭代时刷新 View ，否则我认为 ItemAnimator 不是您需要的解决方案。

当 RecyclerView 项目使用 CustomAdapter 出现时，您可以通过以下方式对其进行动画处理:

public class CustomAdapter extends RecyclerView.Adapter<CustomAdapter.ViewHolder>
{
    private Context context;

    // The items to display in your RecyclerView
    private ArrayList<String> items;
    // Allows to remember the last item shown on screen
    private int lastPosition = -1;

    public static class ViewHolder extends RecyclerView.ViewHolder
    {
        TextView text;
        // You need to retrieve the container (ie the root ViewGroup from your custom_item_layout)
        // It's the view that will be animated
        FrameLayout container;

        public ViewHolder(View itemView)
        {
            super(itemView);
            container = (FrameLayout) itemView.findViewById(R.id.item_layout_container);
            text = (TextView) itemView.findViewById(R.id.item_layout_text);
        }
    }

    public CustomAdapter(ArrayList<String> items, Context context)
    {
        this.items = items;
        this.context = context;
    }

    @Override
    public CustomAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType)
    {
        View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.custom_item_layout, parent, false);
        return new ViewHolder(v);
    }

    @Override
    public void onBindViewHolder(ViewHolder holder, int position)
    {
        holder.text.setText(items.get(position));

        // Here you apply the animation when the view is bound
        setAnimation(holder.itemView, position);
    }

    /**
     * Here is the key method to apply the animation
     */
    private void setAnimation(View viewToAnimate, int position)
    {
        // If the bound view wasn't previously displayed on screen, it's animated
        if (position > lastPosition)
        {
            Animation animation = AnimationUtils.loadAnimation(context, android.R.anim.slide_in_left);
            viewToAnimate.startAnimation(animation);
            lastPosition = position;
        }
    }
}

您的 custom_item_layout 看起来像这样:

<FrameLayout
    android:id="@+id/item_layout_container"
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <TextView
        android:id="@+id/item_layout_text"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceListItemSmall"
        android:gravity="center_vertical"
        android:minHeight="?android:attr/listPreferredItemHeightSmall"/>

</FrameLayout>

有关 CustomAdapters 和 RecyclerView 的更多信息，请参阅 training on the official documentation .

快速滚动问题

使用此方法可能会导致快速滚动出现问题。在动画发生时可以重用 View 。为了避免这种情况，建议在分离时清除动画。

    @Override
    public void onViewDetachedFromWindow(final RecyclerView.ViewHolder holder)
    {
        ((CustomViewHolder)holder).clearAnimation();
    }

在 CustomViewHolder 上:

    public void clearAnimation()
    {
        mRootLayout.clearAnimation();
    }

旧答案:

看看Gabriele Mariotti's repo , 我很确定你会找到你需要的。他为 RecyclerView 提供了简单的 ItemAnimator，例如 SlideInItemAnimator 或 SlideScaleItemAnimator。