滚动时动画 RecyclerView [英] Animate RecyclerView when scrolling

问题描述

当我滚动 RecyclerView 时，有什么方法可以为它的元素设置动画吗?

Is there any way to animate the elements of a RecyclerView when I scroll it?

我查看了 DefaultItemAnimator 和 RecyclerView.ItemAnimator，但似乎只有在数据集发生变化时才会调用动画，如果我错了，请纠正我.

I took a look at DefaultItemAnimator and RecyclerView.ItemAnimator, but that animations seems to be only called if the dataset has changed, please correct me if I am wrong.

我对 RecyclerView.ItemAnimator.animateMove() 什么时候调用它有点困惑?我在该类中设置了一些断点，但没有一个会停止我的应用程序.

I'm a little confused about RecyclerView.ItemAnimator.animateMove() when is it called? I put some breakpoints into that class but none of them stops my app.

但是回到我的问题，如何为 RecyclerView 设置动画?我希望某些元素具有另一种不透明度，这取决于某些自定义规则.

However back to my question how can I animate the RecyclerView? I want that some elements have another opacity, depended on some custom rules.

我做了一些更多的研究，似乎动画移动正是我正在寻找的.这些方法是从 dispatchLayout() 调用的.这是该方法的 javadoc:

I did some more reaseach it seems that animation move is exactly that what I'm looking for. That methods are called from dispatchLayout(). Here is the javadoc of that method:

layoutChildren() 周围的包装器，用于处理由布局引起的动画变化.动画的工作假设有五种不同的项目在玩:
持久性:项目在布局前后可见
REMOVED:项目在布局之前可见并被应用程序删除
添加:项目在布局之前不存在并且是由应用程序添加的
DISAPPEARING:项目存在于数据集中之前/之后，但从在布局过程中可见到不可见(它们被移开屏幕作为其他更改的副作用)
APPEARING:项目存在于数据集中之前/之后，但从在布局过程中不可见到可见(它们被移动了屏幕作为其他更改的副作用)
整体方法确定布局之前/之后存在哪些项目，以及为每个项目推断上述五个状态之一.然后是动画进行了相应的设置:
PERSISTENT 视图被移动 ({@link ItemAnimator#animateMove(ViewHolder, int, int, int, int)})REMOVED 视图被移除 ({@link ItemAnimator#animateRemove(ViewHolder)})
添加了添加的视图 ({@link ItemAnimator#animateAdd(ViewHolder)})
DISAPPEARING 视图已移出屏幕
APPEARING 视图在屏幕上移动

Wrapper around layoutChildren() that handles animating changes caused by layout. Animations work on the assumption that there are five different kinds of items in play:
PERSISTENT: items are visible before and after layout
REMOVED: items were visible before layout and were removed by the app
ADDED: items did not exist before layout and were added by the app
DISAPPEARING: items exist in the data set before/after, but changed from visible to non-visible in the process of layout (they were moved off screen as a side-effect of other changes)
APPEARING: items exist in the data set before/after, but changed from non-visible to visible in the process of layout (they were moved on screen as a side-effect of other changes)
The overall approach figures out what items exist before/after layout and infers one of the five above states for each of the items. Then the animations are set up accordingly:
PERSISTENT views are moved ({@link ItemAnimator#animateMove(ViewHolder, int, int, int, int)}) REMOVED views are removed ({@link ItemAnimator#animateRemove(ViewHolder)})
ADDED views are added ({@link ItemAnimator#animateAdd(ViewHolder)})
DISAPPEARING views are moved off screen
APPEARING views are moved on screen

到目前为止，我正在寻找 PERSISTENT、DISAPPEARING 和 APPEARING，但由于这里的这一行，这些方法从未被调用:

So far I'm looking for PERSISTENT, DISAPPEARING and APPEARING, but that methods are never called because of this line here:

boolean animateChangesSimple = mItemAnimator != null && mItemsAddedOrRemoved
            && !mItemsChanged;

mItemsAddedOrRemoved 总是假的，所以没有一个回调被到达.知道如何正确设置设置标志吗?

mItemsAddedOrRemoved is simply always false so none of that callback are ever reached. Any idea how to set set flag correctly?

推荐答案

我最终使用了 OnScrollListener 并在自定义 animate() 方法中对其进行了动画处理.在我的情况下，代码只需要 2 毫秒，因此对于 60fps 来说没有问题.

I ended in using an OnScrollListener and animating it in a custom animate() method. In my case that code takes just 2ms so that is no problem for the 60fps.

recyclerView.setOnScrollListener(new RecyclerView.OnScrollListener() {
    @Override
    public void onScrollStateChanged(int newState) {
        if(newState == RecyclerView.SCROLL_STATE_IDLE) {
            // special handler to avoid displaying half elements
            scrollToNext();
        }
        animate();
    }

    @Override
    public void onScrolled(int dx, int dy) {
        animate();
    }
});

这篇关于滚动时动画 RecyclerView的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！