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
如果你想要物品周围的间距和物品大小相等,下面是一步一步的简单解决方案。
ItemOffsetDecoration
public class ItemOffsetDecoration extends RecyclerView.ItemDecoration {
private int mItemOffset;
public ItemOffsetDecoration(int itemOffset) {
mItemOffset = itemOffset;
}
public ItemOffsetDecoration(@NonNull Context context, @DimenRes int itemOffsetId) {
this(context.getResources().getDimensionPixelSize(itemOffsetId));
}
@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent,
RecyclerView.State state) {
super.getItemOffsets(outRect, view, parent, state);
outRect.set(mItemOffset, mItemOffset, mItemOffset, mItemOffset);
}
}
实现
在源代码中,将ItemOffsetDecoration添加到RecyclerView中。 项偏移值应该是实际值的一半大小,作为项之间的空间。
mRecyclerView.setLayoutManager(new GridLayoutManager(context, NUM_COLUMNS);
ItemOffsetDecoration itemDecoration = new ItemOffsetDecoration(context, R.dimen.item_offset);
mRecyclerView.addItemDecoration(itemDecoration);
同样,设置项目偏移值为itsRecyclerView的填充,并指定android:clipToPadding=false。
<android.support.v7.widget.RecyclerView
android:id="@+id/recyclerview_grid"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:clipToPadding="false"
android:padding="@dimen/item_offset"/>
其他回答
如果你想在所有设备中固定你的RecyclerView项的大小。你可以这样做
public class GridSpacingItemDecoration extends RecyclerView.ItemDecoration {
private int mSpanCount;
private float mItemSize;
public GridSpacingItemDecoration(int spanCount, int itemSize) {
this.mSpanCount = spanCount;
mItemSize = itemSize;
}
@Override
public void getItemOffsets(final Rect outRect, final View view, RecyclerView parent,
RecyclerView.State state) {
final int position = parent.getChildLayoutPosition(view);
final int column = position % mSpanCount;
final int parentWidth = parent.getWidth();
int spacing = (int) (parentWidth - (mItemSize * mSpanCount)) / (mSpanCount + 1);
outRect.left = spacing - column * spacing / mSpanCount;
outRect.right = (column + 1) * spacing / mSpanCount;
if (position < mSpanCount) {
outRect.top = spacing;
}
outRect.bottom = spacing;
}
}
recyclerview_item.xml
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="@dimen/recycler_view_item_width"
...
>
...
</LinearLayout>
dimens.xml
<dimen name="recycler_view_item_width">60dp</dimen>
活动
int numberOfColumns = 3;
mRecyclerView.setLayoutManager(new GridLayoutManager(this, numberOfColumns));
mRecyclerView.setAdapter(...);
mRecyclerView.addItemDecoration(new GridSpacingItemDecoration(3,
getResources().getDimensionPixelSize(R.dimen.recycler_view_item_width)));
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));
感谢edwardaa的回答https://stackoverflow.com/a/30701422/2227031
另一点需要注意的是:
如果total spacing和total itemWidth不等于屏幕宽度,您还需要调整itemWidth,例如,在适配器onBindViewHolder方法
Utils.init(_mActivity);
int width = 0;
if (includeEdge) {
width = ScreenUtils.getScreenWidth() - spacing * (spanCount + 1);
} else {
width = ScreenUtils.getScreenWidth() - spacing * (spanCount - 1);
}
int itemWidth = width / spanCount;
ConstraintLayout.LayoutParams layoutParams = (ConstraintLayout.LayoutParams) holder.imageViewAvatar.getLayoutParams();
// suppose the width and height are the same
layoutParams.width = itemWidth;
layoutParams.height = itemWidth;
holder.imageViewAvatar.setLayoutParams(layoutParams);
我最后用GridLayoutManager和HeaderView为我的RecyclerView做了这样的事情。
在下面的代码中,我在每个项目之间设置了4dp空间(每个项目周围都是2dp,整个RecyclerView周围是2dp填充)。
在layout.xml:
<android.support.v7.widget.RecyclerView
android:id="@+id/recycleview"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="2dp" />
在你的片段/活动中:
GridLayoutManager manager = new GridLayoutManager(getContext(), 3);
recyclerView.setLayoutManager(manager);
int spacingInPixels = Utils.dpToPx(2);
recyclerView.addItemDecoration(new SpacesItemDecoration(spacingInPixels));
创建SpaceItemDecoration.java:
public class SpacesItemDecoration extends RecyclerView.ItemDecoration {
private int mSpacing;
public SpacesItemDecoration(int spacing) {
mSpacing = spacing;
}
@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView recyclerView, RecyclerView.State state) {
outRect.left = mSpacing;
outRect.top = mSpacing;
outRect.right = mSpacing;
outRect.bottom = mSpacing;
}
}
在Utils.java:
public static int dpToPx(final float dp) {
return Math.round(dp * (Resources.getSystem().getDisplayMetrics().xdpi / DisplayMetrics.DENSITY_DEFAULT));
}
这就是最后对我有用的方法:
binding.rows.addItemDecoration(object: RecyclerView.ItemDecoration() {
val px = resources.getDimensionPixelSize(R.dimen.grid_spacing)
val spanCount = 2
override fun getItemOffsets(outRect: Rect, view: View, parent: RecyclerView, state: RecyclerView.State) {
val index = parent.getChildLayoutPosition(view)
val isLeft = (index % spanCount == 0)
outRect.set(
if (isLeft) px else px/2,
0,
if (isLeft) px/2 else px,
px
)
}
})
因为我只有2列(val spanCount = 2),我可以只做isLeft。如果有> 2列,那么我也需要一个isMiddle,两边的值都是px/2。
我希望有一种方法来获得应用程序:spanCount从直接从RecyclerView,但我不相信有。
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