如何使用gridlayoutmanager在接收器视图中离散滚动？

Question

我正在将RecyclerView与GridLayoutManager一起使用，并将其设置为水平滚动。我希望它离散滚动。这是我启动时的显示方式。

当我滚动一点时，它应该一直滚动直到下一个项目完全可见（又名是离散的）并且在此之前不要停止。它应该看起来像这样。

，它应该这样结束。

我该如何离散滚动？任何指导或帮助将不胜感激！

Answer 1

我在项目中使用了SnapHelper，只需在util包中创建一个类，然后这样做即可。

public class MySnapHelper extends LinearSnapHelper {

private OrientationHelper verticalHelper, horizontalHelper;

public MySnapHelper() {

}

@Override
public void attachToRecyclerView(@Nullable RecyclerView recyclerView)
        throws IllegalStateException {
    super.attachToRecyclerView(recyclerView);
}

@Override
public int[] calculateDistanceToFinalSnap(@NonNull RecyclerView.LayoutManager layoutManager,
                                          @NonNull View targetView) {
    int[] out = new int[2];

    if (layoutManager.canScrollHorizontally()) {
        out[0] = distanceToStart(targetView, getHorizontalHelper(layoutManager));
    } else {
        out[0] = 0;
    }

    if (layoutManager.canScrollVertically()) {
        out[1] = distanceToStart(targetView, getVerticalHelper(layoutManager));
    } else {
        out[1] = 0;
    }
    return out;
}

@Override
public View findSnapView(RecyclerView.LayoutManager layoutManager) {

    if (layoutManager instanceof LinearLayoutManager) {

        if (layoutManager.canScrollHorizontally()) {
            return getStartView(layoutManager, getHorizontalHelper(layoutManager));
        } else {
            return getStartView(layoutManager, getVerticalHelper(layoutManager));
        }
    }

    return super.findSnapView(layoutManager);
}

private int distanceToStart(View targetView, OrientationHelper helper) {
    return helper.getDecoratedStart(targetView) - helper.getStartAfterPadding();
}

private View getStartView(RecyclerView.LayoutManager layoutManager,
                          OrientationHelper helper) {

    if (layoutManager instanceof LinearLayoutManager) {
        int firstChild = ((LinearLayoutManager) layoutManager).findFirstVisibleItemPosition();

        boolean isLastItem = ((LinearLayoutManager) layoutManager)
                .findLastCompletelyVisibleItemPosition()
                == layoutManager.getItemCount() - 1;

        if (firstChild == RecyclerView.NO_POSITION || isLastItem) {
            return null;
        }

        View child = layoutManager.findViewByPosition(firstChild);

        if (helper.getDecoratedEnd(child) >= helper.getDecoratedMeasurement(child) / 2
                && helper.getDecoratedEnd(child) > 0) {
            return child;
        } else {
            if (((LinearLayoutManager) layoutManager).findLastCompletelyVisibleItemPosition()
                    == layoutManager.getItemCount() - 1) {
                return null;
            } else {
                return layoutManager.findViewByPosition(firstChild + 1);
            }
        }
    }

    return super.findSnapView(layoutManager);
}

private OrientationHelper getVerticalHelper(RecyclerView.LayoutManager layoutManager) {
    if (verticalHelper == null) {
        verticalHelper = OrientationHelper.createVerticalHelper(layoutManager);
    }
    return verticalHelper;
}

private OrientationHelper getHorizontalHelper(RecyclerView.LayoutManager layoutManager) {
    if (horizontalHelper == null) {
        horizontalHelper = OrientationHelper.createHorizontalHelper(layoutManager);
    }
    return horizontalHelper;
}

}

，然后将其附加到您的recyclerview中，如下所示：

SnapHelper mySnapHelper = new MySnapHelper ();
mySnapHelper.attachToRecyclerView(mRecyclerView);