检测完成动画在Android的RecyclerView [英] Detect animation finish in Android's RecyclerView

问题描述

的 RecyclerView ，不像到的ListView ，并没有一个简单的方法来一个空的视图设置为它，所以人们必须手动管理它，使空视图可见适配器的项目计数的情况下为0。

The RecyclerView, unlike to ListView, doesn't have a simple way to set an empty view to it, so one has to manage it manually, making empty view visible in case of adapter's item count is 0.

实现这个，一开始我试图修改垫层结构之后有权要求空视图逻辑（的ArrayList 在我的情况），例如：

Implementing this, at first I tried to call empty view logic right after modifying underlaying structure (ArrayList in my case), for example:

btnRemoveFirst.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        devices.remove(0); // remove item from ArrayList
        adapter.notifyItemRemoved(0); // notify RecyclerView's adapter
        updateEmptyView();
    }
});

它做的事情，但有一个缺点：被移除的最后一个元素时，空视图的出现动画之前删除完毕后，取出后立即的。所以我决定要等到动画结束，然后更新UI。

It does the thing, but has a drawback: when the last element is being removed, empty view appears before animation of removing is finished, immediately after removal. So I decided to wait until end of animation and then update UI.

要我惊讶的是，我找不到听在RecyclerView动画事件的好方法。即将在脑海中的第一件事就是用 isRunning 的方法是这样的：

To my surprise, I couldn't find a good way to listen for animation events in RecyclerView. First thing coming to mind is to use isRunning method like this:

btnRemoveFirst.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        devices.remove(0); // remove item from ArrayList
        adapter.notifyItemRemoved(0); // notify RecyclerView's adapter
        recyclerView.getItemAnimator().isRunning(new RecyclerView.ItemAnimator.ItemAnimatorFinishedListener() {
            @Override
            public void onAnimationsFinished() {
                updateEmptyView();
            }
        });
    }
});

不幸的是，回调在这种情况下立即运行，因为在那一刻，内心 ItemAnimator 仍然没有在运行状态。所以，问题是：如何正确使用ItemAnimator.isRunning（）方法并有更好的方式来达到预期的效果，即显示空视图后，单一元素的去除动画完成

Unfortunately, callback in this case runs immediately, because at that moment inner ItemAnimator still isn't in the "running" state. So, the questions are: how to properly use ItemAnimator.isRunning() method and is there a better way to achieve the desired result, i.e. show empty view after removal animation of the single element is finished?

推荐答案

目前我已经找到了解决这个问题的唯一工作方式是延长ItemAnimator，并把它传递给RecyclerView是这样的：

Currently the only working way I've found to solve this problem is to extend ItemAnimator and pass it to RecyclerView like this:

recyclerView.setItemAnimator(new DefaultItemAnimator() {
    @Override
    public void onAnimationFinished(RecyclerView.ViewHolder viewHolder) {
        updateEmptyView();
    }
});

但这种技术并不普遍，因为我已经从具体的实施ItemAnimator延长正在使用的RecyclerView。在里面CoolRecyclerView私有内部CoolItemAnimator的情况下，我的方法将无法工作。

But this technique is not universal, because I have to extend from concrete ItemAnimator implementation being used by RecyclerView. In case of private inner CoolItemAnimator inside CoolRecyclerView, my method will not work at all.

PS：我的同事建议包裹ItemAnimator的装饰以下面的方式：

PS: My colleague suggested to wrap ItemAnimator inside the decorator in a following manner:

recyclerView.setItemAnimator(new ListenableItemAnimator(recyclerView.getItemAnimator()));

这将是很好，尽管看起来矫枉过正这样一个简单的任务，但在这种情况下，创造了装饰是不可能的，无论如何，因为ItemAnimator有一个方法使用setListener（），这是包保护的，所以我显然不能把它包装，以及一些最后的方法。

It would be nice, despite seems like overkill for a such trivial task, but creating the decorator in this case is not possible anyway, because ItemAnimator has a method setListener() which is package protected so I obviously can't wrap it, as well as several final methods.

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