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要實(shí)現(xiàn)RecyclerView列表項(xiàng)頭部懸浮固定,可以使用RecyclerView的ItemDecoration來實(shí)現(xiàn)。下面是一個(gè)實(shí)現(xiàn)的示例代碼:
public class StickyHeaderItemDecoration extends RecyclerView.ItemDecoration {
private static final int HEADER_VIEW_TYPE = 1;
private LayoutInflater mLayoutInflater;
private Context mContext;
private int mHeaderLayoutId;
private int mHeaderTextViewId;
private SparseArray<View> mHeaderViews;
public StickyHeaderItemDecoration(Context context, int headerLayoutId, int headerTextViewId) {
mLayoutInflater = LayoutInflater.from(context);
mContext = context;
mHeaderLayoutId = headerLayoutId;
mHeaderTextViewId = headerTextViewId;
mHeaderViews = new SparseArray<>();
}
@Override
public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {
super.onDrawOver(c, parent, state);
int childCount = parent.getChildCount();
if (childCount == 0) {
return;
}
for (int i = 0; i < childCount; i++) {
View child = parent.getChildAt(i);
int position = parent.getChildAdapterPosition(child);
if (isHeader(position)) {
View headerView = getHeaderView(parent, position);
drawHeader(parent, c, headerView);
}
}
}
private View getHeaderView(RecyclerView parent, int position) {
int headerPosition = getHeaderPositionForItem(position);
int layoutResId = getHeaderLayout(headerPosition);
View headerView = mHeaderViews.get(headerPosition);
if (headerView == null) {
headerView = mLayoutInflater.inflate(layoutResId, parent, false);
mHeaderViews.put(headerPosition, headerView);
}
bindHeaderView(headerView, headerPosition);
return headerView;
}
private void bindHeaderView(View headerView, int position) {
TextView textView = headerView.findViewById(mHeaderTextViewId);
textView.setText("Header " + position);
}
private boolean isHeader(int position) {
return position == 0 || position == 5 || position == 10; // 指定哪些位置為頭部
}
private int getHeaderPositionForItem(int position) {
return position - position / 6;
}
private int getHeaderLayout(int headerPosition) {
return mHeaderLayoutId;
}
private void drawHeader(RecyclerView parent, Canvas c, View headerView) {
c.save();
c.translate(0, parent.getPaddingTop());
headerView.draw(c);
c.restore();
}
}
在Activity或Fragment中使用StickyHeaderItemDecoration:
StickyHeaderItemDecoration itemDecoration = new StickyHeaderItemDecoration(this, R.layout.layout_header, R.id.tv_header);
recyclerView.addItemDecoration(itemDecoration);
上面的代碼中,StickyHeaderItemDecoration類實(shí)現(xiàn)了RecyclerView的ItemDecoration接口,并在onDrawOver方法中繪制頭部懸浮固定的視圖。在getHeaderView方法中獲取頭部視圖并綁定數(shù)據(jù),根據(jù)isHeader方法判斷當(dāng)前位置是否為頭部,然后在onDrawOver方法中繪制頭部視圖。
在Activity或Fragment中,創(chuàng)建StickyHeaderItemDecoration對(duì)象并添加到RecyclerView的ItemDecoration中即可實(shí)現(xiàn)RecyclerView列表項(xiàng)頭部懸浮固定的效果。
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