在RecyclerView的ItemAnimator上禁用onChange动画 [英] Disable onChange animations on ItemAnimator for RecyclerView

问题描述

我正在使用RecyclerView，并使用SortedListAdapterCallback从SortedList获得数据.我想为onChange事件禁用动画，但为onInserted/onRemoved/onMoved保留动画.我尝试在RecyclerView使用的DefaultItemAnimator上调用setSupportsChangeAnimations(false)，但是动画仍然出现.如果我拨打setItemAnimator(null) 所有动画，将按预期成功删除.

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，如果supportsChangeAnimations是true，则RecyclerView会通过保留旧的viewHolder并将其交叉淡入新的viewHolder中来为更改事件设置动画.我不要如果supportsChangeAnimations为false，则旧的和新的viewHolders将是同一对象，并且将出现一个从x到x的onMoved动画(即没有实际移动).但是，这意味着该项目将获得烦人的反弹效果.我也不想要那个，我根本不需要动画. :(

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. :(

从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);
    }
    ...

有时候，当我加载列表时，我会异步地获取一些数据并更新项目1-3次，并且每次反弹和闪烁时，它看起来都非常糟糕.

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动画而无需编写完全自定义的ItemAnimator?

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

推荐答案

浏览代码(我正在使用支持库25.2.0):setSupportsChangeAnimations(<value>)是抽象类SimpleItemAnimator的一种方法，它也是DefaultItemAnimator的超类.在内部，它修改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.

用DefaultItemAnimator的代码执行文本搜索，发现没有查询mSupportsChangeAnimations或getSupportsChangeAnimations()-> DefaultItemAnimator确实忽略了此标志.

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(...)以了解为什么在不运行动画时需要调用dispatchChangeFinished(...)的原因.

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

当没有动画要运行时，也许有一种更优雅的方式来编写else分支，但是，,，这可以实现所需的行为.

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，但希望对您有帮助！

Kind'of late, but hope this helps!

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