如何使用GridLayoutManager与RecyclerView设置列间距? 在我的布局中设置空白/填充没有效果。
当前回答
public class GridSpacingItemDecoration extends RecyclerView.ItemDecoration {
private int spanCount;
private int spacing;
private boolean includeEdge;
public GridSpacingItemDecoration(int spanCount, int spacing, boolean includeEdge) {
this.spanCount = spanCount;
this.spacing = spacing;
this.includeEdge = includeEdge;
}
@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
StaggeredGridLayoutManager.LayoutParams params = (StaggeredGridLayoutManager.LayoutParams) view.getLayoutParams();
int column = params.getSpanIndex();
if (includeEdge) {
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 {
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
}
}
}
}
与edwardaa的回答略有不同，不同之处在于列是如何确定的，因为在一些情况下，例如具有不同高度的项目，列不能简单地通过% spanCount确定
其他回答
选择的答案几乎是完美的，但根据空间的不同，项目的宽度可能不相等。(对我来说，这很关键)。所以我最终用这个代码增加了一点空间，所以项目都是相同的宽度。
class GridSpacingItemDecoration(private val columnCount: Int, @Px preferredSpace: Int, private val includeEdge: Boolean): RecyclerView.ItemDecoration() {
/**
* In this algorithm space should divide by 3 without remnant or width of items can have a difference
* and we want them to be exactly the same
*/
private val space = if (preferredSpace % 3 == 0) preferredSpace else (preferredSpace + (3 - preferredSpace % 3))
override fun getItemOffsets(outRect: Rect, view: View, parent: RecyclerView, state: RecyclerView.State?) {
val position = parent.getChildAdapterPosition(view)
if (includeEdge) {
when {
position % columnCount == 0 -> {
outRect.left = space
outRect.right = space / 3
}
position % columnCount == columnCount - 1 -> {
outRect.right = space
outRect.left = space / 3
}
else -> {
outRect.left = space * 2 / 3
outRect.right = space * 2 / 3
}
}
if (position < columnCount) {
outRect.top = space
}
outRect.bottom = space
} else {
when {
position % columnCount == 0 -> outRect.right = space * 2 / 3
position % columnCount == columnCount - 1 -> outRect.left = space * 2 / 3
else -> {
outRect.left = space / 3
outRect.right = space / 3
}
}
if (position >= columnCount) {
outRect.top = space
}
}
}
}
下面是一个不需要“spanCount”(列数)的解决方案 我使用它是因为我使用GridAutofitLayoutManager(根据所需的单元格大小计算列数)
(注意，这将只工作在GridLayoutManager)
public class GridSpacesItemDecoration extends RecyclerView.ItemDecoration {
private final boolean includeEdge;
private int spacing;
public GridSpacesItemDecoration(int spacing, boolean includeEdge) {
this.spacing = spacing;
this.includeEdge = includeEdge;
}
@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
if (parent.getLayoutManager() instanceof GridLayoutManager) {
GridLayoutManager layoutManager = (GridLayoutManager)parent.getLayoutManager();
int spanCount = layoutManager.getSpanCount();
int position = parent.getChildAdapterPosition(view); // item position
int column = position % spanCount; // item column
if (includeEdge) {
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 {
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
}
}
}
}
}
这是GridAutofitLayoutManager是谁感兴趣:
public class GridAutofitLayoutManager extends GridLayoutManager {
private int mColumnWidth;
private boolean mColumnWidthChanged = true;
public GridAutofitLayoutManager(Context context, int columnWidth)
{
/* Initially set spanCount to 1, will be changed automatically later. */
super(context, 1);
setColumnWidth(checkedColumnWidth(context, columnWidth));
}
public GridAutofitLayoutManager(Context context,int unit, int columnWidth)
{
/* Initially set spanCount to 1, will be changed automatically later. */
super(context, 1);
int pixColumnWidth = (int) TypedValue.applyDimension(unit, columnWidth, context.getResources().getDisplayMetrics());
setColumnWidth(checkedColumnWidth(context, pixColumnWidth));
}
public GridAutofitLayoutManager(Context context, int columnWidth, int orientation, boolean reverseLayout)
{
/* Initially set spanCount to 1, will be changed automatically later. */
super(context, 1, orientation, reverseLayout);
setColumnWidth(checkedColumnWidth(context, columnWidth));
}
private int checkedColumnWidth(Context context, int columnWidth)
{
if (columnWidth <= 0)
{
/* Set default columnWidth value (48dp here). It is better to move this constant
to static constant on top, but we need context to convert it to dp, so can't really
do so. */
columnWidth = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 48,
context.getResources().getDisplayMetrics());
}
return columnWidth;
}
public void setColumnWidth(int newColumnWidth)
{
if (newColumnWidth > 0 && newColumnWidth != mColumnWidth)
{
mColumnWidth = newColumnWidth;
mColumnWidthChanged = true;
}
}
@Override
public void onLayoutChildren(RecyclerView.Recycler recycler, RecyclerView.State state)
{
int width = getWidth();
int height = getHeight();
if (mColumnWidthChanged && mColumnWidth > 0 && width > 0 && height > 0)
{
int totalSpace;
if (getOrientation() == VERTICAL)
{
totalSpace = width - getPaddingRight() - getPaddingLeft();
}
else
{
totalSpace = height - getPaddingTop() - getPaddingBottom();
}
int spanCount = Math.max(1, totalSpace / mColumnWidth);
setSpanCount(spanCount);
mColumnWidthChanged = false;
}
super.onLayoutChildren(recycler, state);
}
}
最后:
mDevicePhotosView.setLayoutManager(new GridAutofitLayoutManager(getContext(), getResources().getDimensionPixelSize(R.dimen.item_size)));
mDevicePhotosView.addItemDecoration(new GridSpacesItemDecoration(Util.dpToPx(getContext(), 2),true));
下面的代码工作得很好，每个列都有相同的宽度:
public class GridSpacingItemDecoration extends RecyclerView.ItemDecoration {
private int spanCount;
private int spacing;
private boolean includeEdge;
public GridSpacingItemDecoration(int spanCount, int spacing, boolean includeEdge) {
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) {
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 {
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
}
}
}
}
使用
1. 没有优势
int spanCount = 3; // 3 columns
int spacing = 50; // 50px
boolean includeEdge = false;
recyclerView.addItemDecoration(new GridSpacingItemDecoration(spanCount, spacing, includeEdge));
2. 与边缘
int spanCount = 3; // 3 columns
int spacing = 50; // 50px
boolean includeEdge = true;
recyclerView.addItemDecoration(new GridSpacingItemDecoration(spanCount, spacing, includeEdge));
我根据edwardaa的回答做了一个Kotlin版本
class RecyclerItemDecoration(private val spanCount: Int, private val spacing: Int) : RecyclerView.ItemDecoration() {
override fun getItemOffsets(outRect: Rect, view: View, parent: RecyclerView, state: RecyclerView.State) {
val spacing = Math.round(spacing * parent.context.resources.displayMetrics.density)
val position = parent.getChildAdapterPosition(view)
val column = position % spanCount
outRect.left = spacing - column * spacing / spanCount
outRect.right = (column + 1) * spacing / spanCount
outRect.top = if (position < spanCount) spacing else 0
outRect.bottom = spacing
}
}
这是我在Kotlin中编写的更灵活的版本，您可以在dp中设置参数。
class ItemDividerGrid(private val numberOfColumns: Int, private val rowSpacingDP: Float = 0f, private val columnSpacingDP: Float = 0f, private val edgeSpacingVerticalDP: Float = 0f, private val edgeSpacingHorizontalDP: Float = 0f) : ItemDecoration() {
override fun getItemOffsets(outRect: Rect, view: View, parent: RecyclerView, state: RecyclerView.State) {
val position = parent.getChildAdapterPosition(view)
val numberOfRows = (parent.adapter?.itemCount?:-1)/numberOfColumns
val column = position % numberOfColumns
val row = position / numberOfColumns
val context = view.context
///horizontal
when(column){
0 -> {
outRect.left = convertDpToPixel(edgeSpacingVerticalDP,context)
outRect.right = convertDpToPixel(columnSpacingDP/2, context)
}
numberOfColumns-1 -> {
outRect.left = convertDpToPixel(columnSpacingDP/2, context)
outRect.right = convertDpToPixel(edgeSpacingVerticalDP, context)
}
else -> {
outRect.left = convertDpToPixel(columnSpacingDP/2, context)
outRect.right = convertDpToPixel(columnSpacingDP/2, context)
}
}
//vertical
when(row){
0 -> {
outRect.top = convertDpToPixel(edgeSpacingHorizontalDP,context)
outRect.bottom = convertDpToPixel(rowSpacingDP/2, context)
}
numberOfRows -> {
outRect.top = convertDpToPixel(rowSpacingDP/2, context)
outRect.bottom = convertDpToPixel(edgeSpacingHorizontalDP, context)
}
else -> {
outRect.top = convertDpToPixel(rowSpacingDP/2, context)
outRect.bottom = convertDpToPixel(rowSpacingDP/2, context)
}
}
}
fun convertDpToPixel(dp: Float, context: Context?): Int {
return if (context != null) {
val resources = context.resources
val metrics = resources.displayMetrics
(dp * (metrics.densityDpi.toFloat() / DisplayMetrics.DENSITY_DEFAULT)).roundToInt()
} else {
val metrics = Resources.getSystem().displayMetrics
(dp * (metrics.densityDpi.toFloat() / DisplayMetrics.DENSITY_DEFAULT)).roundToInt()
}
}
}
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