如何在 RecyclerView 中均匀分布两种不同大小的视图类型？
How to spread evenly two view types with different sizes in RecyclerView?
我在我的 RecyclerView 中为原生广告视图添加了一个新的视图类型，但我不知道如何在整个屏幕上均匀地分布项目。在每第 12 个元素之后，应插入新的视图类型。
这就是我想要的：
这就是我得到的：
第二张图片的结果是使用此代码实现的：
gridLayoutManager = new GridLayoutManager(mActivity, 6);
gridLayoutManager.setSpanSizeLookup(new GridLayoutManager.SpanSizeLookup() {
@Override
public int getSpanSize(int position) {
switch (emotesAdapter.getItemViewType(position)) {
case AD_TYPE:
return gridLayoutManager.getSpanCount();
case CONTENT_TYPE:
return 1;
default:
return -1;
}
}
});
recyclerView.setLayoutManager(gridLayoutManager);
有什么想法吗？
选项 1：
使用 Nick Butcher 的 SpannedGridLayoutManager 作为 RecyclerView 的布局管理器
示例：
recyclerView.setLayoutManager(new SpannedGridLayoutManager(
new SpannedGridLayoutManager.GridSpanLookup() {
@Override
public SpannedGridLayoutManager.SpanInfo getSpanInfo(int position) {
if (position == 0) {
return new SpannedGridLayoutManager.SpanInfo(2, 2);
} else {
return new SpannedGridLayoutManager.SpanInfo(1, 1);
}
}
},
3 /* 3 columns */,
1f /* We want our items to be 1:1 ratio */));
选项 2：
使用FlexboxLayoutManager (within RecyclerView)
RecyclerView recyclerView = (RecyclerView) context.findViewById(R.id.recyclerview);
FlexboxLayoutManager layoutManager = new FlexboxLayoutManager(context);
layoutManager.setFlexDirection(FlexDirection.COLUMN);
layoutManager.setJustifyContent(JustifyContent.FLEX_END);
recyclerView.setLayoutManager(layoutManager);
mImageView.setImageDrawable(drawable);
ViewGroup.LayoutParams lp = mImageView.getLayoutParams();
if (lp instanceof FlexboxLayoutManager.LayoutParams) {
FlexboxLayoutManager.LayoutParams flexboxLp = (FlexboxLayoutManager.LayoutParams) lp;
flexboxLp.setFlexGrow(1.0f);
flexboxLp.setAlignSelf(AlignSelf.FLEX_END);
}
性能不错
使用 GridLayoutManager 您可以水平而不是垂直跨越项目，因此您得到：
所以，你不能单独使用 GridLayoutManager 来做到这一点；但你需要为此定制 LayoutManager； 提供 SpannableGridLayoutManager 自定义水平和垂直跨度大小：
public class SpannableGridLayoutManager extends RecyclerView.LayoutManager {
private GridSpanLookup spanLookup;
private final int columns;
private float cellAspectRatio = 1f;
private int cellHeight;
private int[] cellBorders;
private int firstVisiblePosition;
private int lastVisiblePosition;
private int firstVisibleRow;
private int lastVisibleRow;
private boolean forceClearOffsets;
private SparseArray<GridCell> cells;
private List<Integer> firstChildPositionForRow; // key == row, val == first child position
private int totalRows;
private final Rect itemDecorationInsets = new Rect();
public SpannableGridLayoutManager(GridSpanLookup spanLookup, int columns) {
this.spanLookup = spanLookup;
this.columns = columns;
}
public interface GridSpanLookup {
SpanInfo getSpanInfo(int position);
}
public void setSpanLookup(@NonNull GridSpanLookup spanLookup) {
this.spanLookup = spanLookup;
}
public static class SpanInfo {
public int columnSpan;
public int rowSpan;
public SpanInfo(int columnSpan, int rowSpan) {
this.columnSpan = columnSpan;
this.rowSpan = rowSpan;
}
public static final SpanInfo SINGLE_CELL = new SpanInfo(1, 1);
}
public static class LayoutParams extends RecyclerView.LayoutParams {
int columnSpan;
int rowSpan;
public LayoutParams(Context c, AttributeSet attrs) {
super(c, attrs);
}
public LayoutParams(int width, int height) {
super(width, height);
}
public LayoutParams(ViewGroup.MarginLayoutParams source) {
super(source);
}
public LayoutParams(ViewGroup.LayoutParams source) {
super(source);
}
public LayoutParams(RecyclerView.LayoutParams source) {
super(source);
}
}
@Override
public void onLayoutChildren(RecyclerView.Recycler recycler, RecyclerView.State state) {
calculateWindowSize();
calculateCellPositions(recycler, state);
if (state.getItemCount() == 0) {
detachAndScrapAttachedViews(recycler);
firstVisibleRow = 0;
resetVisibleItemTracking();
return;
}
// TODO use orientationHelper
int startTop = getPaddingTop();
int scrollOffset = 0;
if (forceClearOffsets) { // see #scrollToPosition
startTop = -(firstVisibleRow * cellHeight);
forceClearOffsets = false;
} else if (getChildCount() != 0) {
scrollOffset = getDecoratedTop(getChildAt(0));
startTop = scrollOffset - (firstVisibleRow * cellHeight);
resetVisibleItemTracking();
}
detachAndScrapAttachedViews(recycler);
int row = firstVisibleRow;
int availableSpace = getHeight() - scrollOffset;
int lastItemPosition = state.getItemCount() - 1;
while (availableSpace > 0 && lastVisiblePosition < lastItemPosition) {
availableSpace -= layoutRow(row, startTop, recycler, state);
row = getNextSpannedRow(row);
}
layoutDisappearingViews(recycler, state, startTop);
}
@Override
public RecyclerView.LayoutParams generateDefaultLayoutParams() {
return new LayoutParams(
ViewGroup.LayoutParams.WRAP_CONTENT,
ViewGroup.LayoutParams.WRAP_CONTENT);
}
@Override
public RecyclerView.LayoutParams generateLayoutParams(Context c, AttributeSet attrs) {
return new LayoutParams(c, attrs);
}
@Override
public RecyclerView.LayoutParams generateLayoutParams(ViewGroup.LayoutParams lp) {
if (lp instanceof ViewGroup.MarginLayoutParams) {
return new LayoutParams((ViewGroup.MarginLayoutParams) lp);
} else {
return new LayoutParams(lp);
}
}
@Override
public boolean checkLayoutParams(RecyclerView.LayoutParams lp) {
return lp instanceof LayoutParams;
}
@Override
public void onAdapterChanged(RecyclerView.Adapter oldAdapter, RecyclerView.Adapter newAdapter) {
removeAllViews();
reset();
}
@Override
public boolean supportsPredictiveItemAnimations() {
return true;
}
@Override
public boolean canScrollVertically() {
return true;
}
@Override
public int scrollVerticallyBy(int dy, RecyclerView.Recycler recycler, RecyclerView.State state) {
if (getChildCount() == 0 || dy == 0) return 0;
int scrolled;
int top = getDecoratedTop(getChildAt(0));
if (dy < 0) { // scrolling content down
if (firstVisibleRow == 0) { // at top of content
int scrollRange = -(getPaddingTop() - top);
scrolled = Math.max(dy, scrollRange);
} else {
scrolled = dy;
}
if (top - scrolled >= 0) { // new top row came on screen
int newRow = firstVisibleRow - 1;
if (newRow >= 0) {
int startOffset = top - (firstVisibleRow * cellHeight);
layoutRow(newRow, startOffset, recycler, state);
}
}
int firstPositionOfLastRow = getFirstPositionInSpannedRow(lastVisibleRow);
int lastRowTop = getDecoratedTop(
getChildAt(firstPositionOfLastRow - firstVisiblePosition));
if (lastRowTop - scrolled > getHeight()) { // last spanned row scrolled out
recycleRow(lastVisibleRow, recycler, state);
}
} else { // scrolling content up
int bottom = getDecoratedBottom(getChildAt(getChildCount() - 1));
if (lastVisiblePosition == getItemCount() - 1) { // is at end of content
int scrollRange = Math.max(bottom - getHeight() + getPaddingBottom(), 0);
scrolled = Math.min(dy, scrollRange);
} else {
scrolled = dy;
}
if ((bottom - scrolled) < getHeight()) { // new row scrolled in
int nextRow = lastVisibleRow + 1;
if (nextRow < getSpannedRowCount()) {
int startOffset = top - (firstVisibleRow * cellHeight);
layoutRow(nextRow, startOffset, recycler, state);
}
}
int lastPositionInRow = getLastPositionInSpannedRow(firstVisibleRow, state);
int bottomOfFirstRow =
getDecoratedBottom(getChildAt(lastPositionInRow - firstVisiblePosition));
if (bottomOfFirstRow - scrolled < 0) { // first spanned row scrolled out
recycleRow(firstVisibleRow, recycler, state);
}
}
offsetChildrenVertical(-scrolled);
return scrolled;
}
@Override
public void scrollToPosition(int position) {
if (position >= getItemCount()) position = getItemCount() - 1;
firstVisibleRow = getRowIndex(position);
resetVisibleItemTracking();
forceClearOffsets = true;
removeAllViews();
requestLayout();
}
@Override
public void smoothScrollToPosition(
RecyclerView recyclerView, RecyclerView.State state, int position) {
if (position >= getItemCount()) position = getItemCount() - 1;
LinearSmoothScroller scroller = new LinearSmoothScroller(recyclerView.getContext()) {
@Override
public PointF computeScrollVectorForPosition(int targetPosition) {
final int rowOffset = getRowIndex(targetPosition) - firstVisibleRow;
return new PointF(0, rowOffset * cellHeight);
}
};
scroller.setTargetPosition(position);
startSmoothScroll(scroller);
}
@Override
public int computeVerticalScrollRange(@NonNull RecyclerView.State state) {
// TODO update this to incrementally calculate
return getSpannedRowCount() * cellHeight + getPaddingTop() + getPaddingBottom();
}
@Override
public int computeVerticalScrollExtent(@NonNull RecyclerView.State state) {
return getHeight();
}
@Override
public int computeVerticalScrollOffset(@NonNull RecyclerView.State state) {
if (getChildCount() == 0) return 0;
return getPaddingTop() + (firstVisibleRow * cellHeight) - getDecoratedTop(getChildAt(0));
}
@Override
public View findViewByPosition(int position) {
if (position < firstVisiblePosition || position > lastVisiblePosition) return null;
return getChildAt(position - firstVisiblePosition);
}
public int getFirstVisibleItemPosition() {
return firstVisiblePosition;
}
private static class GridCell {
final int row;
final int rowSpan;
final int column;
final int columnSpan;
GridCell(int row, int rowSpan, int column, int columnSpan) {
this.row = row;
this.rowSpan = rowSpan;
this.column = column;
this.columnSpan = columnSpan;
}
}
/**
* This is the main layout algorithm, iterates over all items and places them into [column, row]
* cell positions. Stores this layout info for use later on. Also records the adapter position
* that each row starts at.
* <p>
* Note that if a row is spanned, then the row start position is recorded as the first cell of
* the row that the spanned cell starts in. This is to ensure that we have sufficient contiguous
* views to layout/draw a spanned row.
*/
private void calculateCellPositions(RecyclerView.Recycler recycler, RecyclerView.State state) {
final int itemCount = state.getItemCount();
cells = new SparseArray<>(itemCount);
firstChildPositionForRow = new ArrayList<>();
int row = 0;
int column = 0;
recordSpannedRowStartPosition(row, column);
int[] rowHWM = new int[columns]; // row high water mark (per column)
for (int position = 0; position < itemCount; position++) {
SpanInfo spanInfo;
int adapterPosition = recycler.convertPreLayoutPositionToPostLayout(position);
if (adapterPosition != RecyclerView.NO_POSITION) {
spanInfo = spanLookup.getSpanInfo(adapterPosition);
} else {
// item removed from adapter, retrieve its previous span info
// as we can't get from the lookup (adapter)
spanInfo = getSpanInfoFromAttachedView(position);
}
if (spanInfo.columnSpan > columns) {
spanInfo.columnSpan = columns; // or should we throw?
}
// check horizontal space at current position else start a new row
// note that this may leave gaps in the grid; we don't backtrack to try and fit
// subsequent cells into gaps. We place the responsibility on the adapter to provide
// continuous data i.e. that would not span column boundaries to avoid gaps.
if (column + spanInfo.columnSpan > columns) {
row++;
recordSpannedRowStartPosition(row, position);
column = 0;
}
// check if this cell is already filled (by previous spanning cell)
while (rowHWM[column] > row) {
column++;
if (column + spanInfo.columnSpan > columns) {
row++;
recordSpannedRowStartPosition(row, position);
column = 0;
}
}
// by this point, cell should fit at [column, row]
cells.put(position, new GridCell(row, spanInfo.rowSpan, column, spanInfo.columnSpan));
// update the high water mark book-keeping
for (int columnsSpanned = 0; columnsSpanned < spanInfo.columnSpan; columnsSpanned++) {
rowHWM[column + columnsSpanned] = row + spanInfo.rowSpan;
}
// if we're spanning rows then record the 'first child position' as the first item
// *in the row the spanned item starts*. i.e. the position might not actually sit
// within the row but it is the earliest position we need to render in order to fill
// the requested row.
if (spanInfo.rowSpan > 1) {
int rowStartPosition = getFirstPositionInSpannedRow(row);
for (int rowsSpanned = 1; rowsSpanned < spanInfo.rowSpan; rowsSpanned++) {
int spannedRow = row + rowsSpanned;
recordSpannedRowStartPosition(spannedRow, rowStartPosition);
}
}
// increment the current position
column += spanInfo.columnSpan;
}
totalRows = rowHWM[0];
for (int i = 1; i < rowHWM.length; i++) {
if (rowHWM[i] > totalRows) {
totalRows = rowHWM[i];
}
}
}
private SpanInfo getSpanInfoFromAttachedView(int position) {
for (int i = 0; i < getChildCount(); i++) {
View child = getChildAt(i);
if (position == getPosition(child)) {
LayoutParams lp = (LayoutParams) child.getLayoutParams();
return new SpanInfo(lp.columnSpan, lp.rowSpan);
}
}
// errrrr?
return SpanInfo.SINGLE_CELL;
}
private void recordSpannedRowStartPosition(final int rowIndex, final int position) {
if (getSpannedRowCount() < (rowIndex + 1)) {
firstChildPositionForRow.add(position);
}
}
private int getRowIndex(final int position) {
return position < cells.size() ? cells.get(position).row : -1;
}
private int getSpannedRowCount() {
return firstChildPositionForRow.size();
}
private int getNextSpannedRow(int rowIndex) {
int firstPositionInRow = getFirstPositionInSpannedRow(rowIndex);
int nextRow = rowIndex + 1;
while (nextRow < getSpannedRowCount()
&& getFirstPositionInSpannedRow(nextRow) == firstPositionInRow) {
nextRow++;
}
return nextRow;
}
private int getFirstPositionInSpannedRow(int rowIndex) {
return firstChildPositionForRow.get(rowIndex);
}
private int getLastPositionInSpannedRow(final int rowIndex, RecyclerView.State state) {
int nextRow = getNextSpannedRow(rowIndex);
return (nextRow != getSpannedRowCount()) ? // check if reached boundary
getFirstPositionInSpannedRow(nextRow) - 1
: state.getItemCount() - 1;
}
/**
* Lay out a given 'row'. We might actually add more that one row if the requested row contains
* a row-spanning cell. Returns the pixel height of the rows laid out.
* <p>
* To simplify logic & book-keeping, views are attached in adapter order, that is child 0 will
* always be the earliest position displayed etc.
*/
private int layoutRow(
int rowIndex, int startTop, RecyclerView.Recycler recycler, RecyclerView.State state) {
int firstPositionInRow = getFirstPositionInSpannedRow(rowIndex);
int lastPositionInRow = getLastPositionInSpannedRow(rowIndex, state);
boolean containsRemovedItems = false;
int insertPosition = (rowIndex < firstVisibleRow) ? 0 : getChildCount();
for (int position = firstPositionInRow;
position <= lastPositionInRow;
position++, insertPosition++) {
View view = recycler.getViewForPosition(position);
LayoutParams lp = (LayoutParams) view.getLayoutParams();
containsRemovedItems |= lp.isItemRemoved();
GridCell cell = cells.get(position);
addView(view, insertPosition);
// TODO use orientation helper
int wSpec = getChildMeasureSpec(
cellBorders[cell.column + cell.columnSpan] - cellBorders[cell.column],
View.MeasureSpec.EXACTLY, 0, lp.width, false);
int hSpec = getChildMeasureSpec(cell.rowSpan * cellHeight,
View.MeasureSpec.EXACTLY, 0, lp.height, true);
measureChildWithDecorationsAndMargin(view, wSpec, hSpec);
int left = cellBorders[cell.column] + lp.leftMargin;
int top = startTop + (cell.row * cellHeight) + lp.topMargin;
int right = left + getDecoratedMeasuredWidth(view);
int bottom = top + getDecoratedMeasuredHeight(view);
layoutDecorated(view, left, top, right, bottom);
lp.columnSpan = cell.columnSpan;
lp.rowSpan = cell.rowSpan;
}
if (firstPositionInRow < firstVisiblePosition) {
firstVisiblePosition = firstPositionInRow;
firstVisibleRow = getRowIndex(firstVisiblePosition);
}
if (lastPositionInRow > lastVisiblePosition) {
lastVisiblePosition = lastPositionInRow;
lastVisibleRow = getRowIndex(lastVisiblePosition);
}
if (containsRemovedItems) return 0; // don't consume space for rows with disappearing items
GridCell first = cells.get(firstPositionInRow);
GridCell last = cells.get(lastPositionInRow);
return (last.row + last.rowSpan - first.row) * cellHeight;
}
/**
* Remove and recycle all items in this 'row'. If the row includes a row-spanning cell then all
* cells in the spanned rows will be removed.
*/
private void recycleRow(
int rowIndex, RecyclerView.Recycler recycler, RecyclerView.State state) {
int firstPositionInRow = getFirstPositionInSpannedRow(rowIndex);
int lastPositionInRow = getLastPositionInSpannedRow(rowIndex, state);
int toRemove = lastPositionInRow;
while (toRemove >= firstPositionInRow) {
int index = toRemove - firstVisiblePosition;
removeAndRecycleViewAt(index, recycler);
toRemove--;
}
if (rowIndex == firstVisibleRow) {
firstVisiblePosition = lastPositionInRow + 1;
firstVisibleRow = getRowIndex(firstVisiblePosition);
}
if (rowIndex == lastVisibleRow) {
lastVisiblePosition = firstPositionInRow - 1;
lastVisibleRow = getRowIndex(lastVisiblePosition);
}
}
private void layoutDisappearingViews(
RecyclerView.Recycler recycler, RecyclerView.State state, int startTop) {
// TODO
}
private void calculateWindowSize() {
// TODO use OrientationHelper#getTotalSpace
int cellWidth =
(int) Math.floor((getWidth() - getPaddingLeft() - getPaddingRight()) / columns);
cellHeight = (int) Math.floor(cellWidth * (1f / cellAspectRatio));
calculateCellBorders();
}
private void reset() {
cells = null;
firstChildPositionForRow = null;
firstVisiblePosition = 0;
firstVisibleRow = 0;
lastVisiblePosition = 0;
lastVisibleRow = 0;
cellHeight = 0;
forceClearOffsets = false;
}
private void resetVisibleItemTracking() {
// maintain the firstVisibleRow but reset other state vars
// TODO make orientation agnostic
int minimumVisibleRow = getMinimumFirstVisibleRow();
if (firstVisibleRow > minimumVisibleRow) firstVisibleRow = minimumVisibleRow;
firstVisiblePosition = getFirstPositionInSpannedRow(firstVisibleRow);
lastVisibleRow = firstVisibleRow;
lastVisiblePosition = firstVisiblePosition;
}
private int getMinimumFirstVisibleRow() {
int maxDisplayedRows = (int) Math.ceil((float) getHeight() / cellHeight) + 1;
if (totalRows < maxDisplayedRows) return 0;
int minFirstRow = totalRows - maxDisplayedRows;
// adjust to spanned rows
return getRowIndex(getFirstPositionInSpannedRow(minFirstRow));
}
/* Adapted from GridLayoutManager */
private void calculateCellBorders() {
cellBorders = new int[columns + 1];
int totalSpace = getWidth() - getPaddingLeft() - getPaddingRight();
int consumedPixels = getPaddingLeft();
cellBorders[0] = consumedPixels;
int sizePerSpan = totalSpace / columns;
int sizePerSpanRemainder = totalSpace % columns;
int additionalSize = 0;
for (int i = 1; i <= columns; i++) {
int itemSize = sizePerSpan;
additionalSize += sizePerSpanRemainder;
if (additionalSize > 0 && (columns - additionalSize) < sizePerSpanRemainder) {
itemSize += 1;
additionalSize -= columns;
}
consumedPixels += itemSize;
cellBorders[i] = consumedPixels;
}
}
private void measureChildWithDecorationsAndMargin(View child, int widthSpec, int heightSpec) {
calculateItemDecorationsForChild(child, itemDecorationInsets);
RecyclerView.LayoutParams lp = (RecyclerView.LayoutParams) child.getLayoutParams();
widthSpec = updateSpecWithExtra(widthSpec, lp.leftMargin + itemDecorationInsets.left,
lp.rightMargin + itemDecorationInsets.right);
heightSpec = updateSpecWithExtra(heightSpec, lp.topMargin + itemDecorationInsets.top,
lp.bottomMargin + itemDecorationInsets.bottom);
child.measure(widthSpec, heightSpec);
}
private int updateSpecWithExtra(int spec, int startInset, int endInset) {
if (startInset == 0 && endInset == 0) {
return spec;
}
int mode = View.MeasureSpec.getMode(spec);
if (mode == View.MeasureSpec.AT_MOST || mode == View.MeasureSpec.EXACTLY) {
return View.MeasureSpec.makeMeasureSpec(
View.MeasureSpec.getSize(spec) - startInset - endInset, mode);
}
return spec;
}
/* Adapted from ConstraintLayout */
private void parseAspectRatio(String aspect) {
if (aspect != null) {
int colonIndex = aspect.indexOf(':');
if (colonIndex >= 0 && colonIndex < aspect.length() - 1) {
String nominator = aspect.substring(0, colonIndex);
String denominator = aspect.substring(colonIndex + 1);
if (nominator.length() > 0 && denominator.length() > 0) {
try {
float nominatorValue = Float.parseFloat(nominator);
float denominatorValue = Float.parseFloat(denominator);
if (nominatorValue > 0 && denominatorValue > 0) {
cellAspectRatio = Math.abs(nominatorValue / denominatorValue);
return;
}
} catch (NumberFormatException e) {
// Ignore
}
}
}
}
throw new IllegalArgumentException("Could not parse aspect ratio: '" + aspect + "'");
}
}
那么在构建的时候可以自定义第十二项的跨度大小：
SpannableGridLayoutManager gridLayoutManager = new
SpannableGridLayoutManager(position -> {
if (position == 12) {
return new SpannableGridLayoutManager.SpanInfo(2, 2); // Setting horizontal & vertical span size
} else {
return new SpannableGridLayoutManager.SpanInfo(1, 1);
}
}, 6); // 6 is the number of column
recyclerview.setLayoutManager(gridLayoutManager);
这是使用过的适配器：
public class RecyclerAdapter extends RecyclerView.Adapter<RecyclerAdapter.CustomViewHolder> {
@NonNull
@Override
public CustomViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int i) {
View listItem = LayoutInflater.from(parent.getContext())
.inflate(R.layout.list_item, parent, false);
return new CustomViewHolder(listItem);
}
@Override
public void onBindViewHolder(@NonNull CustomViewHolder holder, final int position) {
if (position < 12)
holder.tvItemNo.setText(String.valueOf(position + 1));
else if (position == 12)
holder.tvItemNo.setText("1");
else
holder.tvItemNo.setText(String.valueOf(position));
}
@Override
public int getItemCount() {
return 32;
}
class CustomViewHolder extends RecyclerView.ViewHolder {
TextView tvItemNo;
CustomViewHolder(@NonNull View listItem) {
super(listItem);
GridLayoutManager.LayoutParams layoutParams = new
GridLayoutManager.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,
ViewGroup.LayoutParams.MATCH_PARENT);
float margin = convertDpToPixel(listItem.getResources(), 10);
layoutParams.setMargins((int) margin, (int) margin, (int) margin,
(int) margin);
listItem.setLayoutParams(layoutParams);
tvItemNo = listItem.findViewById(R.id.tv_item_no);
}
}
private float convertDpToPixel(Resources r, int dp) {
return TypedValue.applyDimension(
TypedValue.COMPLEX_UNIT_DIP,
dp,
r.getDisplayMetrics()
);
}
}
After every 12th element, the new view type should be inserted.
Likewise you can add do some checks do achieve that:
SpannableGridLayoutManager gridLayoutManager = new
SpannableGridLayoutManager(position -> {
int offset = position / 12 - 1;
if ((position + 1) % 12 != 0 && (position - offset) % 12 == 0) {
return new SpannableGridLayoutManager.SpanInfo(2, 2);
} else {
return new SpannableGridLayoutManager.SpanInfo(1, 1);
}
}, 6);
更新：
The top mentioned method has some issues when scrolling the RecyclerView like adding extra space or changing cell height. There is an expensive solution to notifyDataSetChanged() when the scrolling is over:
recyclerview.addOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrollStateChanged(@NonNull RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
if (newState == RecyclerView.SCROLL_STATE_IDLE)
runOnUiThread(() -> adapter.notifyDataSetChanged());
}
});
但这很昂贵，并且在 UI 更新之前仍然存在故障。
另一个解决方案
您可以使用 here 中的 SpannedGridLayoutManager；它没有额外的空间、项目大小调整或故障问题：
用法：
val spannedGridLayoutManager = SpannedGridLayoutManager(
orientation = SpannedGridLayoutManager.Orientation.VERTICAL,
spans = 6
).apply {
itemOrderIsStable = true
spanSizeLookup =
SpannedGridLayoutManager.SpanSizeLookup { position ->
val offset = position / 12 - 1
if ((position + 1) % 12 != 0 && (position - offset) % 12 == 0) {
SpanSize(2, 2)
} else {
SpanSize(1, 1)
}
}
}
val recyclerView = findViewById<RecyclerView>(R.id.recyclerview)
recyclerView.apply {
layoutManager = spannedGridLayoutManager
adapter = RecyclerAdapter()
}
我在我的 RecyclerView 中为原生广告视图添加了一个新的视图类型，但我不知道如何在整个屏幕上均匀地分布项目。在每第 12 个元素之后，应插入新的视图类型。
这就是我想要的：
这就是我得到的：
第二张图片的结果是使用此代码实现的：
gridLayoutManager = new GridLayoutManager(mActivity, 6);
gridLayoutManager.setSpanSizeLookup(new GridLayoutManager.SpanSizeLookup() {
@Override
public int getSpanSize(int position) {
switch (emotesAdapter.getItemViewType(position)) {
case AD_TYPE:
return gridLayoutManager.getSpanCount();
case CONTENT_TYPE:
return 1;
default:
return -1;
}
}
});
recyclerView.setLayoutManager(gridLayoutManager);
有什么想法吗？
选项 1：
使用 Nick Butcher 的 SpannedGridLayoutManager 作为 RecyclerView 的布局管理器
示例：
recyclerView.setLayoutManager(new SpannedGridLayoutManager(
new SpannedGridLayoutManager.GridSpanLookup() {
@Override
public SpannedGridLayoutManager.SpanInfo getSpanInfo(int position) {
if (position == 0) {
return new SpannedGridLayoutManager.SpanInfo(2, 2);
} else {
return new SpannedGridLayoutManager.SpanInfo(1, 1);
}
}
},
3 /* 3 columns */,
1f /* We want our items to be 1:1 ratio */));
选项 2：
使用FlexboxLayoutManager (within RecyclerView)
RecyclerView recyclerView = (RecyclerView) context.findViewById(R.id.recyclerview);
FlexboxLayoutManager layoutManager = new FlexboxLayoutManager(context);
layoutManager.setFlexDirection(FlexDirection.COLUMN);
layoutManager.setJustifyContent(JustifyContent.FLEX_END);
recyclerView.setLayoutManager(layoutManager);
mImageView.setImageDrawable(drawable);
ViewGroup.LayoutParams lp = mImageView.getLayoutParams();
if (lp instanceof FlexboxLayoutManager.LayoutParams) {
FlexboxLayoutManager.LayoutParams flexboxLp = (FlexboxLayoutManager.LayoutParams) lp;
flexboxLp.setFlexGrow(1.0f);
flexboxLp.setAlignSelf(AlignSelf.FLEX_END);
}
性能不错
使用 GridLayoutManager 您可以水平而不是垂直跨越项目，因此您得到：
所以，你不能单独使用 GridLayoutManager 来做到这一点；但你需要为此定制 LayoutManager； SpannableGridLayoutManager 自定义水平和垂直跨度大小：
public class SpannableGridLayoutManager extends RecyclerView.LayoutManager {
private GridSpanLookup spanLookup;
private final int columns;
private float cellAspectRatio = 1f;
private int cellHeight;
private int[] cellBorders;
private int firstVisiblePosition;
private int lastVisiblePosition;
private int firstVisibleRow;
private int lastVisibleRow;
private boolean forceClearOffsets;
private SparseArray<GridCell> cells;
private List<Integer> firstChildPositionForRow; // key == row, val == first child position
private int totalRows;
private final Rect itemDecorationInsets = new Rect();
public SpannableGridLayoutManager(GridSpanLookup spanLookup, int columns) {
this.spanLookup = spanLookup;
this.columns = columns;
}
public interface GridSpanLookup {
SpanInfo getSpanInfo(int position);
}
public void setSpanLookup(@NonNull GridSpanLookup spanLookup) {
this.spanLookup = spanLookup;
}
public static class SpanInfo {
public int columnSpan;
public int rowSpan;
public SpanInfo(int columnSpan, int rowSpan) {
this.columnSpan = columnSpan;
this.rowSpan = rowSpan;
}
public static final SpanInfo SINGLE_CELL = new SpanInfo(1, 1);
}
public static class LayoutParams extends RecyclerView.LayoutParams {
int columnSpan;
int rowSpan;
public LayoutParams(Context c, AttributeSet attrs) {
super(c, attrs);
}
public LayoutParams(int width, int height) {
super(width, height);
}
public LayoutParams(ViewGroup.MarginLayoutParams source) {
super(source);
}
public LayoutParams(ViewGroup.LayoutParams source) {
super(source);
}
public LayoutParams(RecyclerView.LayoutParams source) {
super(source);
}
}
@Override
public void onLayoutChildren(RecyclerView.Recycler recycler, RecyclerView.State state) {
calculateWindowSize();
calculateCellPositions(recycler, state);
if (state.getItemCount() == 0) {
detachAndScrapAttachedViews(recycler);
firstVisibleRow = 0;
resetVisibleItemTracking();
return;
}
// TODO use orientationHelper
int startTop = getPaddingTop();
int scrollOffset = 0;
if (forceClearOffsets) { // see #scrollToPosition
startTop = -(firstVisibleRow * cellHeight);
forceClearOffsets = false;
} else if (getChildCount() != 0) {
scrollOffset = getDecoratedTop(getChildAt(0));
startTop = scrollOffset - (firstVisibleRow * cellHeight);
resetVisibleItemTracking();
}
detachAndScrapAttachedViews(recycler);
int row = firstVisibleRow;
int availableSpace = getHeight() - scrollOffset;
int lastItemPosition = state.getItemCount() - 1;
while (availableSpace > 0 && lastVisiblePosition < lastItemPosition) {
availableSpace -= layoutRow(row, startTop, recycler, state);
row = getNextSpannedRow(row);
}
layoutDisappearingViews(recycler, state, startTop);
}
@Override
public RecyclerView.LayoutParams generateDefaultLayoutParams() {
return new LayoutParams(
ViewGroup.LayoutParams.WRAP_CONTENT,
ViewGroup.LayoutParams.WRAP_CONTENT);
}
@Override
public RecyclerView.LayoutParams generateLayoutParams(Context c, AttributeSet attrs) {
return new LayoutParams(c, attrs);
}
@Override
public RecyclerView.LayoutParams generateLayoutParams(ViewGroup.LayoutParams lp) {
if (lp instanceof ViewGroup.MarginLayoutParams) {
return new LayoutParams((ViewGroup.MarginLayoutParams) lp);
} else {
return new LayoutParams(lp);
}
}
@Override
public boolean checkLayoutParams(RecyclerView.LayoutParams lp) {
return lp instanceof LayoutParams;
}
@Override
public void onAdapterChanged(RecyclerView.Adapter oldAdapter, RecyclerView.Adapter newAdapter) {
removeAllViews();
reset();
}
@Override
public boolean supportsPredictiveItemAnimations() {
return true;
}
@Override
public boolean canScrollVertically() {
return true;
}
@Override
public int scrollVerticallyBy(int dy, RecyclerView.Recycler recycler, RecyclerView.State state) {
if (getChildCount() == 0 || dy == 0) return 0;
int scrolled;
int top = getDecoratedTop(getChildAt(0));
if (dy < 0) { // scrolling content down
if (firstVisibleRow == 0) { // at top of content
int scrollRange = -(getPaddingTop() - top);
scrolled = Math.max(dy, scrollRange);
} else {
scrolled = dy;
}
if (top - scrolled >= 0) { // new top row came on screen
int newRow = firstVisibleRow - 1;
if (newRow >= 0) {
int startOffset = top - (firstVisibleRow * cellHeight);
layoutRow(newRow, startOffset, recycler, state);
}
}
int firstPositionOfLastRow = getFirstPositionInSpannedRow(lastVisibleRow);
int lastRowTop = getDecoratedTop(
getChildAt(firstPositionOfLastRow - firstVisiblePosition));
if (lastRowTop - scrolled > getHeight()) { // last spanned row scrolled out
recycleRow(lastVisibleRow, recycler, state);
}
} else { // scrolling content up
int bottom = getDecoratedBottom(getChildAt(getChildCount() - 1));
if (lastVisiblePosition == getItemCount() - 1) { // is at end of content
int scrollRange = Math.max(bottom - getHeight() + getPaddingBottom(), 0);
scrolled = Math.min(dy, scrollRange);
} else {
scrolled = dy;
}
if ((bottom - scrolled) < getHeight()) { // new row scrolled in
int nextRow = lastVisibleRow + 1;
if (nextRow < getSpannedRowCount()) {
int startOffset = top - (firstVisibleRow * cellHeight);
layoutRow(nextRow, startOffset, recycler, state);
}
}
int lastPositionInRow = getLastPositionInSpannedRow(firstVisibleRow, state);
int bottomOfFirstRow =
getDecoratedBottom(getChildAt(lastPositionInRow - firstVisiblePosition));
if (bottomOfFirstRow - scrolled < 0) { // first spanned row scrolled out
recycleRow(firstVisibleRow, recycler, state);
}
}
offsetChildrenVertical(-scrolled);
return scrolled;
}
@Override
public void scrollToPosition(int position) {
if (position >= getItemCount()) position = getItemCount() - 1;
firstVisibleRow = getRowIndex(position);
resetVisibleItemTracking();
forceClearOffsets = true;
removeAllViews();
requestLayout();
}
@Override
public void smoothScrollToPosition(
RecyclerView recyclerView, RecyclerView.State state, int position) {
if (position >= getItemCount()) position = getItemCount() - 1;
LinearSmoothScroller scroller = new LinearSmoothScroller(recyclerView.getContext()) {
@Override
public PointF computeScrollVectorForPosition(int targetPosition) {
final int rowOffset = getRowIndex(targetPosition) - firstVisibleRow;
return new PointF(0, rowOffset * cellHeight);
}
};
scroller.setTargetPosition(position);
startSmoothScroll(scroller);
}
@Override
public int computeVerticalScrollRange(@NonNull RecyclerView.State state) {
// TODO update this to incrementally calculate
return getSpannedRowCount() * cellHeight + getPaddingTop() + getPaddingBottom();
}
@Override
public int computeVerticalScrollExtent(@NonNull RecyclerView.State state) {
return getHeight();
}
@Override
public int computeVerticalScrollOffset(@NonNull RecyclerView.State state) {
if (getChildCount() == 0) return 0;
return getPaddingTop() + (firstVisibleRow * cellHeight) - getDecoratedTop(getChildAt(0));
}
@Override
public View findViewByPosition(int position) {
if (position < firstVisiblePosition || position > lastVisiblePosition) return null;
return getChildAt(position - firstVisiblePosition);
}
public int getFirstVisibleItemPosition() {
return firstVisiblePosition;
}
private static class GridCell {
final int row;
final int rowSpan;
final int column;
final int columnSpan;
GridCell(int row, int rowSpan, int column, int columnSpan) {
this.row = row;
this.rowSpan = rowSpan;
this.column = column;
this.columnSpan = columnSpan;
}
}
/**
* This is the main layout algorithm, iterates over all items and places them into [column, row]
* cell positions. Stores this layout info for use later on. Also records the adapter position
* that each row starts at.
* <p>
* Note that if a row is spanned, then the row start position is recorded as the first cell of
* the row that the spanned cell starts in. This is to ensure that we have sufficient contiguous
* views to layout/draw a spanned row.
*/
private void calculateCellPositions(RecyclerView.Recycler recycler, RecyclerView.State state) {
final int itemCount = state.getItemCount();
cells = new SparseArray<>(itemCount);
firstChildPositionForRow = new ArrayList<>();
int row = 0;
int column = 0;
recordSpannedRowStartPosition(row, column);
int[] rowHWM = new int[columns]; // row high water mark (per column)
for (int position = 0; position < itemCount; position++) {
SpanInfo spanInfo;
int adapterPosition = recycler.convertPreLayoutPositionToPostLayout(position);
if (adapterPosition != RecyclerView.NO_POSITION) {
spanInfo = spanLookup.getSpanInfo(adapterPosition);
} else {
// item removed from adapter, retrieve its previous span info
// as we can't get from the lookup (adapter)
spanInfo = getSpanInfoFromAttachedView(position);
}
if (spanInfo.columnSpan > columns) {
spanInfo.columnSpan = columns; // or should we throw?
}
// check horizontal space at current position else start a new row
// note that this may leave gaps in the grid; we don't backtrack to try and fit
// subsequent cells into gaps. We place the responsibility on the adapter to provide
// continuous data i.e. that would not span column boundaries to avoid gaps.
if (column + spanInfo.columnSpan > columns) {
row++;
recordSpannedRowStartPosition(row, position);
column = 0;
}
// check if this cell is already filled (by previous spanning cell)
while (rowHWM[column] > row) {
column++;
if (column + spanInfo.columnSpan > columns) {
row++;
recordSpannedRowStartPosition(row, position);
column = 0;
}
}
// by this point, cell should fit at [column, row]
cells.put(position, new GridCell(row, spanInfo.rowSpan, column, spanInfo.columnSpan));
// update the high water mark book-keeping
for (int columnsSpanned = 0; columnsSpanned < spanInfo.columnSpan; columnsSpanned++) {
rowHWM[column + columnsSpanned] = row + spanInfo.rowSpan;
}
// if we're spanning rows then record the 'first child position' as the first item
// *in the row the spanned item starts*. i.e. the position might not actually sit
// within the row but it is the earliest position we need to render in order to fill
// the requested row.
if (spanInfo.rowSpan > 1) {
int rowStartPosition = getFirstPositionInSpannedRow(row);
for (int rowsSpanned = 1; rowsSpanned < spanInfo.rowSpan; rowsSpanned++) {
int spannedRow = row + rowsSpanned;
recordSpannedRowStartPosition(spannedRow, rowStartPosition);
}
}
// increment the current position
column += spanInfo.columnSpan;
}
totalRows = rowHWM[0];
for (int i = 1; i < rowHWM.length; i++) {
if (rowHWM[i] > totalRows) {
totalRows = rowHWM[i];
}
}
}
private SpanInfo getSpanInfoFromAttachedView(int position) {
for (int i = 0; i < getChildCount(); i++) {
View child = getChildAt(i);
if (position == getPosition(child)) {
LayoutParams lp = (LayoutParams) child.getLayoutParams();
return new SpanInfo(lp.columnSpan, lp.rowSpan);
}
}
// errrrr?
return SpanInfo.SINGLE_CELL;
}
private void recordSpannedRowStartPosition(final int rowIndex, final int position) {
if (getSpannedRowCount() < (rowIndex + 1)) {
firstChildPositionForRow.add(position);
}
}
private int getRowIndex(final int position) {
return position < cells.size() ? cells.get(position).row : -1;
}
private int getSpannedRowCount() {
return firstChildPositionForRow.size();
}
private int getNextSpannedRow(int rowIndex) {
int firstPositionInRow = getFirstPositionInSpannedRow(rowIndex);
int nextRow = rowIndex + 1;
while (nextRow < getSpannedRowCount()
&& getFirstPositionInSpannedRow(nextRow) == firstPositionInRow) {
nextRow++;
}
return nextRow;
}
private int getFirstPositionInSpannedRow(int rowIndex) {
return firstChildPositionForRow.get(rowIndex);
}
private int getLastPositionInSpannedRow(final int rowIndex, RecyclerView.State state) {
int nextRow = getNextSpannedRow(rowIndex);
return (nextRow != getSpannedRowCount()) ? // check if reached boundary
getFirstPositionInSpannedRow(nextRow) - 1
: state.getItemCount() - 1;
}
/**
* Lay out a given 'row'. We might actually add more that one row if the requested row contains
* a row-spanning cell. Returns the pixel height of the rows laid out.
* <p>
* To simplify logic & book-keeping, views are attached in adapter order, that is child 0 will
* always be the earliest position displayed etc.
*/
private int layoutRow(
int rowIndex, int startTop, RecyclerView.Recycler recycler, RecyclerView.State state) {
int firstPositionInRow = getFirstPositionInSpannedRow(rowIndex);
int lastPositionInRow = getLastPositionInSpannedRow(rowIndex, state);
boolean containsRemovedItems = false;
int insertPosition = (rowIndex < firstVisibleRow) ? 0 : getChildCount();
for (int position = firstPositionInRow;
position <= lastPositionInRow;
position++, insertPosition++) {
View view = recycler.getViewForPosition(position);
LayoutParams lp = (LayoutParams) view.getLayoutParams();
containsRemovedItems |= lp.isItemRemoved();
GridCell cell = cells.get(position);
addView(view, insertPosition);
// TODO use orientation helper
int wSpec = getChildMeasureSpec(
cellBorders[cell.column + cell.columnSpan] - cellBorders[cell.column],
View.MeasureSpec.EXACTLY, 0, lp.width, false);
int hSpec = getChildMeasureSpec(cell.rowSpan * cellHeight,
View.MeasureSpec.EXACTLY, 0, lp.height, true);
measureChildWithDecorationsAndMargin(view, wSpec, hSpec);
int left = cellBorders[cell.column] + lp.leftMargin;
int top = startTop + (cell.row * cellHeight) + lp.topMargin;
int right = left + getDecoratedMeasuredWidth(view);
int bottom = top + getDecoratedMeasuredHeight(view);
layoutDecorated(view, left, top, right, bottom);
lp.columnSpan = cell.columnSpan;
lp.rowSpan = cell.rowSpan;
}
if (firstPositionInRow < firstVisiblePosition) {
firstVisiblePosition = firstPositionInRow;
firstVisibleRow = getRowIndex(firstVisiblePosition);
}
if (lastPositionInRow > lastVisiblePosition) {
lastVisiblePosition = lastPositionInRow;
lastVisibleRow = getRowIndex(lastVisiblePosition);
}
if (containsRemovedItems) return 0; // don't consume space for rows with disappearing items
GridCell first = cells.get(firstPositionInRow);
GridCell last = cells.get(lastPositionInRow);
return (last.row + last.rowSpan - first.row) * cellHeight;
}
/**
* Remove and recycle all items in this 'row'. If the row includes a row-spanning cell then all
* cells in the spanned rows will be removed.
*/
private void recycleRow(
int rowIndex, RecyclerView.Recycler recycler, RecyclerView.State state) {
int firstPositionInRow = getFirstPositionInSpannedRow(rowIndex);
int lastPositionInRow = getLastPositionInSpannedRow(rowIndex, state);
int toRemove = lastPositionInRow;
while (toRemove >= firstPositionInRow) {
int index = toRemove - firstVisiblePosition;
removeAndRecycleViewAt(index, recycler);
toRemove--;
}
if (rowIndex == firstVisibleRow) {
firstVisiblePosition = lastPositionInRow + 1;
firstVisibleRow = getRowIndex(firstVisiblePosition);
}
if (rowIndex == lastVisibleRow) {
lastVisiblePosition = firstPositionInRow - 1;
lastVisibleRow = getRowIndex(lastVisiblePosition);
}
}
private void layoutDisappearingViews(
RecyclerView.Recycler recycler, RecyclerView.State state, int startTop) {
// TODO
}
private void calculateWindowSize() {
// TODO use OrientationHelper#getTotalSpace
int cellWidth =
(int) Math.floor((getWidth() - getPaddingLeft() - getPaddingRight()) / columns);
cellHeight = (int) Math.floor(cellWidth * (1f / cellAspectRatio));
calculateCellBorders();
}
private void reset() {
cells = null;
firstChildPositionForRow = null;
firstVisiblePosition = 0;
firstVisibleRow = 0;
lastVisiblePosition = 0;
lastVisibleRow = 0;
cellHeight = 0;
forceClearOffsets = false;
}
private void resetVisibleItemTracking() {
// maintain the firstVisibleRow but reset other state vars
// TODO make orientation agnostic
int minimumVisibleRow = getMinimumFirstVisibleRow();
if (firstVisibleRow > minimumVisibleRow) firstVisibleRow = minimumVisibleRow;
firstVisiblePosition = getFirstPositionInSpannedRow(firstVisibleRow);
lastVisibleRow = firstVisibleRow;
lastVisiblePosition = firstVisiblePosition;
}
private int getMinimumFirstVisibleRow() {
int maxDisplayedRows = (int) Math.ceil((float) getHeight() / cellHeight) + 1;
if (totalRows < maxDisplayedRows) return 0;
int minFirstRow = totalRows - maxDisplayedRows;
// adjust to spanned rows
return getRowIndex(getFirstPositionInSpannedRow(minFirstRow));
}
/* Adapted from GridLayoutManager */
private void calculateCellBorders() {
cellBorders = new int[columns + 1];
int totalSpace = getWidth() - getPaddingLeft() - getPaddingRight();
int consumedPixels = getPaddingLeft();
cellBorders[0] = consumedPixels;
int sizePerSpan = totalSpace / columns;
int sizePerSpanRemainder = totalSpace % columns;
int additionalSize = 0;
for (int i = 1; i <= columns; i++) {
int itemSize = sizePerSpan;
additionalSize += sizePerSpanRemainder;
if (additionalSize > 0 && (columns - additionalSize) < sizePerSpanRemainder) {
itemSize += 1;
additionalSize -= columns;
}
consumedPixels += itemSize;
cellBorders[i] = consumedPixels;
}
}
private void measureChildWithDecorationsAndMargin(View child, int widthSpec, int heightSpec) {
calculateItemDecorationsForChild(child, itemDecorationInsets);
RecyclerView.LayoutParams lp = (RecyclerView.LayoutParams) child.getLayoutParams();
widthSpec = updateSpecWithExtra(widthSpec, lp.leftMargin + itemDecorationInsets.left,
lp.rightMargin + itemDecorationInsets.right);
heightSpec = updateSpecWithExtra(heightSpec, lp.topMargin + itemDecorationInsets.top,
lp.bottomMargin + itemDecorationInsets.bottom);
child.measure(widthSpec, heightSpec);
}
private int updateSpecWithExtra(int spec, int startInset, int endInset) {
if (startInset == 0 && endInset == 0) {
return spec;
}
int mode = View.MeasureSpec.getMode(spec);
if (mode == View.MeasureSpec.AT_MOST || mode == View.MeasureSpec.EXACTLY) {
return View.MeasureSpec.makeMeasureSpec(
View.MeasureSpec.getSize(spec) - startInset - endInset, mode);
}
return spec;
}
/* Adapted from ConstraintLayout */
private void parseAspectRatio(String aspect) {
if (aspect != null) {
int colonIndex = aspect.indexOf(':');
if (colonIndex >= 0 && colonIndex < aspect.length() - 1) {
String nominator = aspect.substring(0, colonIndex);
String denominator = aspect.substring(colonIndex + 1);
if (nominator.length() > 0 && denominator.length() > 0) {
try {
float nominatorValue = Float.parseFloat(nominator);
float denominatorValue = Float.parseFloat(denominator);
if (nominatorValue > 0 && denominatorValue > 0) {
cellAspectRatio = Math.abs(nominatorValue / denominatorValue);
return;
}
} catch (NumberFormatException e) {
// Ignore
}
}
}
}
throw new IllegalArgumentException("Could not parse aspect ratio: '" + aspect + "'");
}
}
那么在构建的时候可以自定义第十二项的跨度大小：
SpannableGridLayoutManager gridLayoutManager = new
SpannableGridLayoutManager(position -> {
if (position == 12) {
return new SpannableGridLayoutManager.SpanInfo(2, 2); // Setting horizontal & vertical span size
} else {
return new SpannableGridLayoutManager.SpanInfo(1, 1);
}
}, 6); // 6 is the number of column
recyclerview.setLayoutManager(gridLayoutManager);
这是使用过的适配器：
public class RecyclerAdapter extends RecyclerView.Adapter<RecyclerAdapter.CustomViewHolder> {
@NonNull
@Override
public CustomViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int i) {
View listItem = LayoutInflater.from(parent.getContext())
.inflate(R.layout.list_item, parent, false);
return new CustomViewHolder(listItem);
}
@Override
public void onBindViewHolder(@NonNull CustomViewHolder holder, final int position) {
if (position < 12)
holder.tvItemNo.setText(String.valueOf(position + 1));
else if (position == 12)
holder.tvItemNo.setText("1");
else
holder.tvItemNo.setText(String.valueOf(position));
}
@Override
public int getItemCount() {
return 32;
}
class CustomViewHolder extends RecyclerView.ViewHolder {
TextView tvItemNo;
CustomViewHolder(@NonNull View listItem) {
super(listItem);
GridLayoutManager.LayoutParams layoutParams = new
GridLayoutManager.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,
ViewGroup.LayoutParams.MATCH_PARENT);
float margin = convertDpToPixel(listItem.getResources(), 10);
layoutParams.setMargins((int) margin, (int) margin, (int) margin,
(int) margin);
listItem.setLayoutParams(layoutParams);
tvItemNo = listItem.findViewById(R.id.tv_item_no);
}
}
private float convertDpToPixel(Resources r, int dp) {
return TypedValue.applyDimension(
TypedValue.COMPLEX_UNIT_DIP,
dp,
r.getDisplayMetrics()
);
}
}
After every 12th element, the new view type should be inserted. Likewise you can add do some checks do achieve that:
SpannableGridLayoutManager gridLayoutManager = new
SpannableGridLayoutManager(position -> {
int offset = position / 12 - 1;
if ((position + 1) % 12 != 0 && (position - offset) % 12 == 0) {
return new SpannableGridLayoutManager.SpanInfo(2, 2);
} else {
return new SpannableGridLayoutManager.SpanInfo(1, 1);
}
}, 6);
更新：
The top mentioned method has some issues when scrolling the RecyclerView like adding extra space or changing cell height. There is an expensive solution to notifyDataSetChanged() when the scrolling is over:
recyclerview.addOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrollStateChanged(@NonNull RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
if (newState == RecyclerView.SCROLL_STATE_IDLE)
runOnUiThread(() -> adapter.notifyDataSetChanged());
}
});
但这很昂贵，并且在 UI 更新之前仍然存在故障。
另一个解决方案
您可以使用 here 中的 SpannedGridLayoutManager；它没有额外的空间、项目大小调整或故障问题：
用法：
val spannedGridLayoutManager = SpannedGridLayoutManager(
orientation = SpannedGridLayoutManager.Orientation.VERTICAL,
spans = 6
).apply {
itemOrderIsStable = true
spanSizeLookup =
SpannedGridLayoutManager.SpanSizeLookup { position ->
val offset = position / 12 - 1
if ((position + 1) % 12 != 0 && (position - offset) % 12 == 0) {
SpanSize(2, 2)
} else {
SpanSize(1, 1)
}
}
}
val recyclerView = findViewById<RecyclerView>(R.id.recyclerview)
recyclerView.apply {
layoutManager = spannedGridLayoutManager
adapter = RecyclerAdapter()
}