Android:控制在回收站视图上平滑滚动 [英] Android : Control Smooth scroll over recycler view

问题描述

我正在使用带有 CardView 的 Recyclerview.我知道如何控制列表视图上的速度.但不适用于 Recyclerview.

I am using Recyclerview with CardView. I am aware how to control speed on list view. But not for Recyclerview.

我在找到的类名中搜索了很多SmoothScroll.怎么用那个?我不知道！现在 Recyclerview 默认滚动速度很快.

I searched a lot in found class name SmoothScroll. How to use that? I have no Idea! Right now Recyclerview by default scroll is fast.

更新:

我用 this

推荐答案

当您说smoothScroll"时，您不清楚您的意思.您可能指的是自动smoothScrollToPosition"，它会自动滚动到指定位置，您可能指的是手动滚动，也可能指的是投掷.为了繁荣，我现在将尝试回答所有这些问题.

It's unclear what you mean when you say "smoothScroll". You could be referring to the automatic "smoothScrollToPosition" which will automatically scroll to a specified position, you could be talking about manual scrolling and you could be talking about flinging. For the sake of prosperity, I will attempt to answer all of these issues now.

1.自动平滑滚动.

在你的布局管理器中，你需要实现 smoothScrollToPosition 方法:

Inside your layout manager, you need to implement the smoothScrollToPosition method:

    @Override
    public void smoothScrollToPosition(RecyclerView recyclerView, State state, int position)
    {
        // A good idea would be to create this instance in some initialization method, and just set the target position in this method.
        LinearSmoothScroller smoothScroller = new LinearSmoothScroller(getContext())
        {
            @Override
            public PointF computeScrollVectorForPosition(int targetPosition)
            {
                int yDelta = calculateCurrentDistanceToPosition(targetPosition);
                return new PointF(0, yDelta);
            }

            // This is the important method. This code will return the amount of time it takes to scroll 1 pixel.
            // This code will request X milliseconds for every Y DP units.
            @Override
            protected float calculateSpeedPerPixel(DisplayMetrics displayMetrics)
            {
                return X / TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, Y, displayMetrics);
            }

        };
        smoothScroller.setTargetPosition(position);

        startSmoothScroll(smoothScroller);
    }

在这个例子中，我使用了一个名为calculateCurrentDistanceToPosition"的辅助方法.这可能有点棘手，因为它涉及跟踪您当前的滚动位置，并计算给定 y 位置的滚动位置.您可以在 此处 找到有关如何跟踪回收者滚动的示例.一>.

In this example, I use a helper method named "calculateCurrentDistanceToPosition". This can be a bit tricky, since it involves keeping track of your current scroll position, and calculating the scroll position of a given y position. You can find an example of how to keep track of the recycler's scroll y here.

计算给定位置的滚动 y 实际上取决于您的回收站显示的内容.假设您所有的物品高度相同，您可以通过执行以下计算来计算:

Calculating the scroll y of a given position is really dependent on what your recycler is displaying. Assuming all your items are the same height, you can calculate this by performing the following calculation:

targetScrollY = targetPosition * itemHeight

然后，要计算您需要滚动的距离，只需将当前滚动 y 与目标滚动 y 相减即可:

Then, to calculate the distance you need to scroll, simply subtract the current scroll y with the target scroll y:

private int calculateCurrentDistanceToPosition(int targetPosition) {
    int targetScrollY = targetPosition * itemHeight;
    return targetScrollY - currentScrollY;
}

2.降低手动滚动速度.

再次，您需要编辑您的布局管理器，这一次 - scrollVerticallyBy 方法:

Once again, you need to edit your layout manager, this time - the scrollVerticallyBy method:

    @Override
    public int scrollVerticallyBy(int delta, Recycler recycler, State state)
    {
       // write your limiting logic here to prevent the delta from exceeding the limits of your list.

       int prevDelta = delta;
       if (getScrollState() == SCROLL_STATE_DRAGGING)
            delta = (int)(delta > 0 ? Math.max(delta * MANUAL_SCROLL_SLOW_RATIO, 1) : Math.min(delta * MANUAL_SCROLL_SLOW_RATIO, -1));  

       // MANUAL_SCROLL_SLOW_RATIO is between 0 (no manual scrolling) to 1 (normal speed) or more (faster speed).
       // write your scrolling logic code here whereby you move each view by the given delta

        if (getScrollState() == SCROLL_STATE_DRAGGING)
            delta = prevDelta;

        return delta;
    }

在上面的方法中，我调用了getScrollState()".这是RecyclerView 的一个方法.在这个实现中，我的自定义 LayoutManager 是我的自定义 RecyclerView 的嵌套类.如果这对您不起作用，您可以尝试通过某种界面模式获取滚动状态.

In the above method, I call "getScrollState()". This is a method of RecyclerView. In this implementation, my custom LayoutManager is a nested class of my custom RecyclerView. If this doesn't work for you, you can try to grab the scroll state via some interface pattern.

3.放慢投掷速度

在这里，您要按比例降低投掷速度.您将需要覆盖 RecyclerView 子类中的 fling 方法:

Here you want to scale down the fling velocity. You will need to override the fling method inside your RecyclerView subclass:

@Override
public boolean fling(int velocityX, int velocityY)
{
     velocityY *= FLING_SCALE_DOWN_FACTOR; // (between 0 for no fling, and 1 for normal fling, or more for faster fling).

     return super.fling(velocityX, velocityY);
}

我很难提供更量身定制的解决方案，因为您没有发布任何代码，也没有提供有关您的设置的大量信息，但我希望这涵盖了大多数基础，并能帮助您找到最适合您的解决方案.

It's difficult for me to provide a more tailored solution, since you didn't post any of your code, or provide much information about your setup, but I hope this covers most bases and will help you find the best solution for you.

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