关键时刻，第一时间送达！
接上文
第一步：首先我们来写一个类，它起标记的作用，来放每一个item的对应的悬浮栏的字符串
public class NameBean {
String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
第二步：自定义一个SectionDecoration 类 继承 RecyclerView的ItemDecoration
public class SectionDecoration extends RecyclerView.ItemDecoration {
private static final String TAG = 'SectionDecoration';
private List
dataList;
private DecorationCallback callback;
private TextPaint textPaint;
private Paint paint;
private int topGap;
private int alignBottom;
private Paint.FontMetrics fontMetrics;
public SectionDecoration(List
dataList, Context context, DecorationCallback decorationCallback) { Resources res = context.getResources();
this.dataList = dataList;
this.callback = decorationCallback;
//设置悬浮栏的画笔---paint
paint = new Paint();
paint.setColor(res.getColor(R.color.colorGray));
//设置悬浮栏中文本的画笔
textPaint = new TextPaint();
textPaint.setAntiAlias(true);
textPaint.setTextSize(DensityUtil.dip2px(context, 14));
textPaint.setColor(Color.DKGRAY);
textPaint.setTextAlign(Paint.Align.LEFT);
fontMetrics = new Paint.FontMetrics();
//决定悬浮栏的高度等
topGap = res.getDimensionPixelSize(R.dimen.sectioned_top);
//决定文本的显示位置等
alignBottom = res.getDimensionPixelSize(R.dimen.sectioned_alignBottom);
}
@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
super.getItemOffsets(outRect, view, parent, state);
int pos = parent.getChildAdapterPosition(view);
Log.i(TAG, 'getItemOffsets：' + pos);
String groupId = callback.getGroupId(pos);
if (groupId.equals('-1')) return;
//只有是同一组的第一个才显示悬浮栏
if (pos == 0 || isFirstInGroup(pos)) {
outRect.top = topGap;
if (dataList.get(pos).getName() == '') {
outRect.top = 0;
}
} else {
outRect.top = 0;
}
}
@Override
public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
super.onDraw(c, parent, state);
int left = parent.getPaddingLeft();
int right = parent.getWidth() - parent.getPaddingRight();
int childCount = parent.getChildCount();
for (int i = 0; i <>childCount; i++) {
View view = parent.getChildAt(i);
int position = parent.getChildAdapterPosition(view);
String groupId = callback.getGroupId(position);
if (groupId.equals('-1')) return;
String textLine = callback.getGroupFirstLine(position).toUpperCase();
if (textLine == '') {
float top = view.getTop();
float bottom = view.getTop();
c.drawRect(left, top, right, bottom, paint);
return;
} else {
if (position == 0 || isFirstInGroup(position)) {
float top = view.getTop() - topGap;
float bottom = view.getTop();
//绘制悬浮栏
c.drawRect(left, top - topGap, right, bottom, paint);
//绘制文本
c.drawText(textLine, left, bottom, textPaint);
}
}
}
}
@Override
public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {
super.onDrawOver(c, parent, state);
int itemCount = state.getItemCount();
int childCount = parent.getChildCount();
int left = parent.getPaddingLeft();
int right = parent.getWidth() - parent.getPaddingRight();
float lineHeight = textPaint.getTextSize() + fontMetrics.descent;
String preGroupId = '';
String groupId = '-1';
for (int i = 0; i <>childCount; i++) {
View view = parent.getChildAt(i);
int position = parent.getChildAdapterPosition(view);
preGroupId = groupId;
groupId = callback.getGroupId(position);
if (groupId.equals('-1') || groupId.equals(preGroupId)) continue;
String textLine = callback.getGroupFirstLine(position).toUpperCase();
if (TextUtils.isEmpty(textLine)) continue;
int viewBottom = view.getBottom();
float textY = Math.max(topGap, view.getTop());
//下一个和当前不一样移动当前
if (position + 1 <>itemCount) {
String nextGroupId = callback.getGroupId(position + 1);
//组内最后一个view进入了header
if (nextGroupId != groupId && viewBottom <>textY) {
textY = viewBottom;
}
}
//textY - topGap决定了悬浮栏绘制的高度和位置
c.drawRect(left, textY - topGap, right, textY, paint);
//left+2*alignBottom 决定了文本往左偏移的多少（加-->向左移）
//textY-alignBottom 决定了文本往右偏移的多少 (减-->向上移)
c.drawText(textLine, left + 2 * alignBottom, textY - alignBottom, textPaint);
}
}
/**
* 判断是不是组中的第一个位置
*
* @param pos
* @return
*/
private boolean isFirstInGroup(int pos) {
if (pos == 0) {
return true;
} else {
// 因为是根据 字符串内容的相同与否 来判断是不是同意组的，所以此处的标记id 要是String类型
// 如果你只是做联系人列表，悬浮框里显示的只是一个字母，则标记id直接用 int 类型就行了
String prevGroupId = callback.getGroupId(pos - 1);
String groupId = callback.getGroupId(pos);
//判断前一个字符串 与 当前字符串 是否相同
if (prevGroupId.equals(groupId)) {
return false;
} else {
return true;
}
}
}
//定义一个借口方便外界的调用
interface DecorationCallback {
String getGroupId(int position);
String getGroupFirstLine(int position);
}
}
第三步：在向list集合中先把每一个item的 起“标记”作用的字符串都加进去
setPullAction(comingslist);
private void setPullAction(ListWaitMVBean.DataBean.ComingBean> comingslist) {
dataList = new ArrayList<>();
for (int i = 0; i <>comingslist.size(); i++) {
NameBean nameBean = new NameBean();
String name0 = comingslist.get(i).getComingTitle();
nameBean.setName(name0);
dataList.add(nameBean);
}
}
第四步：在setAdapter() 前，为RecyclerView添加ItemDecoration:
recyclerView.addItemDecoration(new SectionDecoration(dataList,mContext, new SectionDecoration.DecorationCallback() {
//返回标记id (即每一项对应的标志性的字符串)
@Override
public String getGroupId(int position) {
if(dataList.get(position).getName()!=null) {
return dataList.get(position).getName();
}
return '-1';
}
//获取同组中的第一个内容
@Override
public String getGroupFirstLine(int position) {
if(dataList.get(position).getName()!=null) {
return dataList.get(position).getName();
}
return '';
}
}));
这样就完成了~
再看一眼最终效果感受一下：
来自：李诗雨
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