为 RecyclerView 禁用 ItemAnimator 上的 onChange 动画 [英] Disable onChange animations on ItemAnimator for RecyclerView

问题描述

我正在使用 RecyclerView 提供来自 SortedList 的数据，使用 SortedListAdapterCallback.我想为 onChange 事件禁用动画，但为 onInserted/onRemoved/onMoved 保留它们.我尝试在 RecyclerView 使用的 DefaultItemAnimator 上调用 setSupportsChangeAnimations(false)，但动画仍然出现.如果我调用 setItemAnimator(null) all 动画会按预期成功删除.

I am using a RecyclerView fed with data from a SortedList using a SortedListAdapterCallback. I want to disable animations for onChange events, but preserve them for onInserted/onRemoved/onMoved. I have tried calling setSupportsChangeAnimations(false) on the DefaultItemAnimator used by the RecyclerView, but the animation still appears. If I call setItemAnimator(null) all animations are successfully removed as expected though.

我尝试查看实现，似乎如果 supportsChangeAnimations 是 true，RecyclerView 将通过保留旧的 viewHolder 来动画更改事件并将其淡入淡出到新的 viewHolder.我不想要那个.如果 supportsChangeAnimations 是 false，那么旧的和新的 viewHolders 将是同一个对象，而是会有一个从 x 到 x 的 onMoved 动画(即，没有实际移动).然而，这意味着该项目将获得令人讨厌的反弹效果.我也不想要那个，我根本不想要动画.:(

I tried looking at the implementation and it seems like if supportsChangeAnimations is true, the RecyclerView will animate change events by keeping the old viewHolder and cross-fade it to the new viewHolder. I don't want that. If supportsChangeAnimations is false, the old and new viewHolders will however be the same object, and there will instead be an onMoved animation from x to x (i.e., no actual move). This however means that the item will get an annoying bounce effect. I don't want that either, I want no animation at all. :(

来自 DefaultItemAnimator.java:

From DefaultItemAnimator.java:

@Override
public boolean animateChange(ViewHolder oldHolder, ViewHolder newHolder,
        int fromX, int fromY, int toX, int toY) {
    if (oldHolder == newHolder) {
        // Don't know how to run change animations when the same view holder is re-used.
        // run a move animation to handle position changes.
        return animateMove(oldHolder, fromX, fromY, toX, toY);
    }
    ...

有时当我加载我的列表时，我会异步获取一些数据并更新项目 1-3 次，而且每次都弹跳和闪烁时看起来真的很糟糕.

Sometimes when I load my list I asynchronously fetch some data and update items 1-3 times, and it looks really crappy when it bounces and flickers every time.

如何有效地完全禁用 onChange 动画而不求助于编写完全自定义的 ItemAnimator?

How do I effectively completely disable onChange animations without resorting to writing a completely custom ItemAnimator?

推荐答案

看代码(我用的是支持库25.2.0):setSupportsChangeAnimations()是一个方法在抽象类 SimpleItemAnimator 上，它也是 DefaultItemAnimator 的超类.在内部，它会修改 mSupportsChangeAnimations 的值.

Looking through the code (I'm using support library 25.2.0): setSupportsChangeAnimations(<value>) is a method on the abstract class SimpleItemAnimator, which is also DefaultItemAnimator's superclass. Internally, it modifies the value of mSupportsChangeAnimations.

在 DefaultItemAnimator 的代码中执行文本搜索，发现 mSupportsChangeAnimations 和 getSupportsChangeAnimations() 都没有被查询 -->code>DefaultItemAnimator 从字面上忽略这个标志.

Performing a text search in DefaultItemAnimator's code, reveals that neither mSupportsChangeAnimations, nor getSupportsChangeAnimations() are queried --> the DefaultItemAnimator literally ignores this flag.

正确的解决方案是按以下方式扩展DefaultItemAnimator:

The correct solution is to extend the DefaultItemAnimator in the following manner:

public class CustomItemAnimator extends DefaultItemAnimator {
@Override
public boolean animateChange(RecyclerView.ViewHolder oldHolder, RecyclerView.ViewHolder newHolder, int fromX, int fromY, int toX, int toY) {
    if (getSupportsChangeAnimations()) {
        return super.animateChange(oldHolder, newHolder, fromX, fromY, toX, toY);
    } else {
        if (oldHolder == newHolder) {
            if (oldHolder != null) {
                //if the two holders are equal, call dispatch change only once
                dispatchChangeFinished(oldHolder, /*ignored*/true);
            }
        } else {
            //else call dispatch change once for every non-null holder
            if (oldHolder != null) {
                dispatchChangeFinished(oldHolder, true);
            }
            if (newHolder != null) {
                dispatchChangeFinished(newHolder, false);
            }
        }
        //we don't need a call to requestPendingTransactions after this, return false.
        return false;
    }
}

请参阅文档 animateChange(...) 以了解为什么在没有运行动画时需要调用 dispatchChangeFinished(...).

See docs animateChange(...) to understand why it was needed to call dispatchChangeFinished(...) when no animations were run.

当没有要运行的动画时，可能有一种更优雅的方式来编写 else 分支，但可惜，这实现了所需的行为.

Probably there's a more elegant way to write the else branch when there are no animations to be run, but alas, this achieves the desired behavior.

有点晚了，但希望这会有所帮助！

Kind'of late, but hope this helps!

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