Android:控制平滑滚动浏览回收站视图 [英] Android : Control Smooth scroll over recycler view

问题描述

我正在将Recyclerview与CardView一起使用.我知道如何控制列表视图的速度.但是对于Recyclerview来说不是.

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

我在找到的类名称 SmoothScroll <中进行了大量搜索/a>.如何使用?我不知道！现在，默认情况下，Recyclerview的滚动速度很快.

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:

我用此

推荐答案

目前尚不清楚您说"smoothScroll"是什么意思.您可能指的是自动"smoothScrollToPosition"，它将自动滚动到指定位置，您可能正在谈论手动滚动，您可能正在谈论猛冲.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.

在布局管理器内部，您需要实现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);
    }

在此示例中，我使用了一个名为"calculateCurrentDistanceToPosition"的辅助方法.这可能有点棘手，因为它涉及跟踪当前滚动位置并计算给定y位置的滚动位置.您可以在此处处找到如何跟踪回收者滚动的示例.

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实际取决于回收商显示的内容.假设所有物品的高度相同，则可以通过以下计算来计算高度:

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.

这一次，您需要再次编辑布局管理器-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;
    }

编辑:在上述方法中，我称为"getScrollState()".这是RecyclerView的方法.在此实现中，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来获取滚动状态.

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.放慢逃跑速度

您要在此处减小下垂速度.您将需要在RecyclerView子类中覆盖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);
}

由于您没有发布任何代码，也没有提供许多有关设置的信息，因此我很难提供更具针对性的解决方案，但我希望这涵盖了大多数基础知识，并将帮助您找到最佳的解决方案

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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