我有一个GridSpacingItemDecoration类,用于管理间距和跨度。
这是代码:

public class GridSpacingItemDecoration extends RecyclerView.ItemDecoration
{
    private int spanCount;
    private int spacing;
    private boolean includeEdge;
    private boolean rtl;

    public GridSpacingItemDecoration(boolean rtl, int spanCount, int spacing, boolean includeEdge)
    {
        this.rtl = rtl;
        this.spanCount = spanCount;
        this.spacing = spacing;
        this.includeEdge = includeEdge;
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state)
    {
        int position = parent.getChildAdapterPosition(view); // item position
        int column = position % spanCount; // item column

        if (includeEdge)
        {
            if (rtl)
            {
                outRect.right = spacing - column * spacing / spanCount; // spacing - column * ((1f / spanCount) * spacing)
                outRect.left = (column + 1) * spacing / spanCount; // (column + 1) * ((1f / spanCount) * spacing)
            }else {
                outRect.left = spacing - column * spacing / spanCount; // spacing - column * ((1f / spanCount) * spacing)
                outRect.right = (column + 1) * spacing / spanCount; // (column + 1) * ((1f / spanCount) * spacing)
            }

            if (position < spanCount)
            { // top edge
                outRect.top = spacing;
            }
            outRect.bottom = spacing; // item bottom
        } else
        {
            if (rtl){
                outRect.right = column * spacing / spanCount; // column * ((1f / spanCount) * spacing)
                outRect.left = spacing - (column + 1) * spacing / spanCount; // spacing - (column + 1) * ((1f /    spanCount) * spacing)
            }else {
                outRect.left = column * spacing / spanCount; // column * ((1f / spanCount) * spacing)
                outRect.right = spacing - (column + 1) * spacing / spanCount; // spacing - (column + 1) * ((1f /    spanCount) * spacing)
            }

            if (position >= spanCount)
            {
                outRect.top = spacing; // item top
            }
        }
    }
}

当我想要有一个或多个列时,它会很好地工作。 (如下图所示-所有间距和跨度均有效)
android - RecyclerView Item装饰间距和跨度-LMLPHP
android - RecyclerView Item装饰间距和跨度-LMLPHP
问题是我想使用具有不同spanType的不同ViewType的RecyclerView。这是我尝试执行的操作:
在类(class)中定义:
public static ArrayList<Integer> type = new ArrayList<>();

private int getTypeForPosition(int position)
{
    return type.get(position);
}

private final int HEADER = 0;
private final int CHILD = 1;
private int dpToPx(int dp)
{
    Resources r = getResources();
    return Math.round(TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dp, r.getDisplayMetrics()));
}

在方法中定义:
type.add(HEADER);
type.add(CHILD);
type.add(CHILD);
type.add(HEADER);
GridLayoutManager glm = new GridLayoutManager(getContext(), 2);
glm.setSpanSizeLookup(new GridLayoutManager.SpanSizeLookup() {
@Override
public int getSpanSize(int position) {
    switch(getTypeForPosition(position)) {
        case HEADER:
            return 2;
        default:
            return 1;
        }
    }
});
recyclerView.setLayoutManager(glm);
recyclerView.addItemDecoration(new GridSpacingItemDecoration(true, 1, dpToPx(8), true));
ClassAdapter classAdapter = new ClassAdapter(getContext(), classes);
recyclerView.setAdapter(classAdapter);

结果如下:
android - RecyclerView Item装饰间距和跨度-LMLPHP

问题是:同一行中两列之间的间隔(如图所示)。好像是16,是我选择的两倍。
问题:如何自定义GridSpacingItemDecoration类以使所有项目之间具有相同的空间?

最佳答案

这是我的主张:

class SearchResultItemDecoration(val space: Int, val NUMBER_OF_COLUMNS: Int) : RecyclerView.ItemDecoration() {

    override fun getItemOffsets(outRect: Rect?, view: View?, parent: RecyclerView?, state: RecyclerView.State?) {
        super.getItemOffsets(outRect, view, parent, state)

        addSpaceToView(outRect, parent?.getChildAdapterPosition(view), parent)
    }

    private fun addSpaceToView(outRect: Rect?, position: Int?, parent: RecyclerView?) {
        if (position == null || parent == null)
            return

        val grid = parent.layoutManager as GridLayoutManager
        val spanSize = grid.spanSizeLookup.getSpanSize(position)

        if (spanSize == NUMBER_OF_COLUMNS) {
            outRect?.right = space
        } else {
            var allSpanSize = 0
            for (i: Int in IntRange(0, position)) {
                allSpanSize += grid.spanSizeLookup.getSpanSize(i)
            }
            val currentModuloResult = allSpanSize % NUMBER_OF_COLUMNS
            if (currentModuloResult == 0) {
                outRect?.right = space
            }
        }
        outRect?.left = space
        outRect?.top = space
    }
}

该代码是用Kotlin编写的,但我希望能以Java开发人员的身份阅读它;)因此,主要的假设是始终在项目的顶部和左侧添加sapce。现在,我们只需要担心在右侧添加空间,为此,我们需要知道该行的右侧是哪个项目。
spanSize是一个值,其中包含有关当前 View 占用多少列的信息。如果占用了该行的所有列,那么显然我们也想添加正确的空间。

那是一个简单的情况。现在,如果我们想为项目添加正确的空间(也位于RecycelrView的右侧),我们需要对其进行计算。 allSpanSize是不计项目位置,但计项目跨度大小的值。这样,我们现在要做的就是使用取模运算来进行简单的数学运算。如果除法的其余部分为0,则当前项在右侧。

我知道,这可能不是最好的解决方案,因为当您在RecycelrView中有很多项目时,可能要花一些时间来计算。为了防止这种情况,您可以讲一些arrayList,该数组保存给定项目的 View 和allSpanSize的位置。

10-07 19:24
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