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)
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:
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。