原文出處：?李詩雨???

開始逐漸領略到ItemDecoration的美~

今天讓我 使用?ItemDecoration?來完成?可推動的懸浮導航欄的效果，最終實現的效果如下圖：

具體實現步驟如下：

根據我前面的文章所講的RecyclerView的基本使用，我們先來完成基本的recyclerView：

第一步：布局里寫一個RecyclerView

第二步：實例化

Java

1	recyclerView = (RecyclerView) findViewById(R.id.recyclerView);

第三步：獲取所需的數據 (這里我們來個真實點的情景，去聯網請求數據)

Java

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/** ????* 聯網請求所需的url ????*/?? ?? public String url="http://api.meituan.com/mmdb/movie/v2/list/rt/order/coming.json?ci=1&limit=12&token=&__vhost=api.maoyan.com&utm_campaign=AmovieBmovieCD-1&movieBundleVersion=6801&utm_source=xiaomi&utm_medium=android&utm_term=6.8.0&utm_content=868030022327462&net=255&dModel=MI%205&uuid=0894DE03C76F6045D55977B6D4E32B7F3C6AAB02F9CEA042987B380EC5687C43&lat=40.100673&lng=116.378619&__skck=6a375bce8c66a0dc293860dfa83833ef&__skts=1463704714271&__skua=7e01cf8dd30a179800a7a93979b430b2&__skno=1a0b4a9b-44ec-42fc-b110-ead68bcc2824&__skcy=sXcDKbGi20CGXQPPZvhCU3%2FkzdE%3D";

?

Java

1 2	//聯網獲取數據?? ?????? getDataFromNet();

?

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/** ???? * 使用okhttpUtils進行聯網請求數據 ???? */?? ????private void getDataFromNet() {?? ????????OkHttpUtils.?? ????????????????get()?? ????????????????.url(url)?? ????????????????.build()?? ????????????????.execute(new StringCallback() {?? ????????????????????@Override?? ????????????????????public void onError(okhttp3.Call call, Exception e, int id) {?? ????????????????????????Log.e("TAG", "聯網失敗" + e.getMessage());?? ????????????????????}?? ?? ????????????????????@Override?? ????????????????????public void onResponse(String response, int id) {?? ????????????????????????Log.e("TAG", "聯網成功==" + response);?? ?? ????????????????????????//聯網成功后使用fastjson解析?? ????????????????????????processData(response);?? ????????????????????}?? ????????????????});?? ????}

?

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/** ???? * 使用fastjson進行解析 ???? * ???? * @param json ???? */?? ????private void processData(String json) {?? ????????//這里使用GsonFormat生成對應的bean類?? ?????? JSONObject jsonObject = parseObject(json);?? ?? ????????String data = jsonObject.getString("data");?? ????????JSONObject dataObj = JSON.parseObject(data);?? ?? ????????String coming = dataObj.getString("coming");?? ????????List<WaitMVBean.DataBean.ComingBean> comingslist = parseArray(coming, WaitMVBean.DataBean.ComingBean.class);?? ?? ????????//測試是否解析數據成功?? //????????String strTest = comingslist.get(0).getCat();?? //????????Log.e("TAG", strTest + "222");?? ?? ???????? //解析數據成功,設置適配器-->?? ???????? ????????}?? ?? ????}

第四步：解析數據成功后，創建并設置適配器,并傳遞相關數據

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//解析數據成功,設置適配器?? ?????????? MyRecyclerAdapter adapter = new MyRecyclerAdapter( mContext,comingslist);?? ?????????? recyclerView.setAdapter(adapter);

適配器：

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public class MyRecyclerAdapter extends RecyclerView.Adapter {?? ?? ????private final List<WaitMVBean.DataBean.ComingBean> comingslist;?? ????private final Context mContext;?? ????private final LayoutInflater mLayoutInflater;?? ?? ?? ????public MyRecyclerAdapter(Context mContext, List<WaitMVBean.DataBean.ComingBean> comingslist) {?? ????????this.mContext = mContext;?? ????????this.comingslist = comingslist;?? ????????mLayoutInflater = LayoutInflater.from(mContext);?? ????}?? ?? ????@Override?? ????public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {?? ????????return new MyViewHolder(mLayoutInflater.inflate(R.layout.date_item, null));?? ????}?? ?? ????@Override?? ????public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {?? ????????MyViewHolder myholder = (MyViewHolder) holder;?? ????????myholder.setData(position);?? ????}?? ?? ????@Override?? ????public int getItemCount() {?? ????????return comingslist.size();?? ????}?? ?? ????class MyViewHolder extends RecyclerView.ViewHolder {?? ????????private TextView mv_name;?? ????????private TextView mv_dec;?? ????????private TextView mv_date;?? ????????private ImageView imageView;?? ?? ????????public MyViewHolder(View itemView) {?? ????????????super(itemView);?? ????????????mv_name = (TextView) itemView.findViewById(R.id.mv_name);?? ????????????mv_dec = (TextView) itemView.findViewById(R.id.mv_dec);?? ????????????mv_date = (TextView) itemView.findViewById(R.id.mv_date);?? ????????????imageView = (ImageView) itemView.findViewById(R.id.image);?? ????????}?? ?? ????????public void setData(int position) {?? ????????????WaitMVBean.DataBean.ComingBean coming = comingslist.get(position);?? ?? ????????????String name = coming.getNm();?? ????????????mv_name.setText(name);?? ?? ????????????String date = coming.getShowInfo();?? ????????????mv_date.setText(date);?? ?? ????????????String dec = coming.getScm();?? ????????????mv_dec.setText(dec);?? ?? ????????????//注：當你發下圖片無法打開是，做個字符串替換即可?? ????????????String imagUrl = coming.getImg();?? ????????????String newImagUrl = imagUrl.replaceAll("w.h", "50.80");?? ?? ????????????//使用Glide加載圖片?? ????????????Glide.with(mContext)?? ????????????????????.load(newImagUrl)?? ????????????????????.into(imageView);?? ????????}?? ????}?? }

item的布局：

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<?xml version="1.0" encoding="utf-8"?>?? <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"?? ????android:layout_width="wrap_content"?? ????android:layout_height="wrap_content"?? ????android:background="#ffffff"?? ????android:gravity="center_vertical"?? ????android:orientation="horizontal">?? ?? ????<ImageView?? ????????android:id="@+id/image"?? ????????android:layout_width="70dp"?? ????????android:layout_height="110dp"?? ????????android:layout_marginBottom="5dp"?? ????????android:layout_marginLeft="10dp"?? ????????android:layout_marginRight="8dp"?? ????????android:layout_marginTop="5dp" />?? ?? ????<LinearLayout?? ????????android:layout_width="0dp"?? ????????android:layout_height="wrap_content"?? ????????android:layout_marginLeft="6dp"?? ????????android:layout_weight="1"?? ????????android:orientation="vertical">?? ?? ????????<TextView?? ????????????android:id="@+id/mv_name"?? ????????????android:layout_width="wrap_content"?? ????????????android:layout_height="wrap_content"?? ????????????android:text="神奇動物在哪裏"?? ????????????android:textColor="#000000"?? ????????????android:textSize="15sp" />?? ?? ????????<LinearLayout?? ????????????android:layout_width="wrap_content"?? ????????????android:layout_height="wrap_content"?? ????????????android:orientation="horizontal">?? ?? ????????????<TextView?? ????????????????android:layout_width="wrap_content"?? ????????????????android:layout_height="wrap_content"?? ????????????????android:text="觀眾"?? ????????????????android:textColor="#55000000"?? ????????????????android:textSize="14sp" />?? ?? ????????????<TextView?? ????????????????android:id="@+id/tv_people"?? ????????????????android:layout_width="wrap_content"?? ????????????????android:layout_height="wrap_content"?? ????????????????android:text="9.0 "?? ????????????????android:textColor="#FFCE42"?? ????????????????android:textSize="18sp" />?? ?? ????????????<TextView?? ????????????????android:layout_width="wrap_content"?? ????????????????android:layout_height="wrap_content"?? ????????????????android:text=" | 專業"?? ????????????????android:textColor="#55000000"?? ????????????????android:textSize="14sp" />?? ?? ????????????<TextView?? ????????????????android:id="@+id/tv_professional"?? ????????????????android:layout_width="wrap_content"?? ????????????????android:layout_height="wrap_content"?? ????????????????android:text="6.7"?? ????????????????android:textColor="#FFCE42"?? ????????????????android:textSize="18sp" />?? ????????</LinearLayout>?? ?????????? ????????<TextView?? ????????????android:id="@+id/mv_dec"?? ????????????android:layout_width="wrap_content"?? ????????????android:layout_height="wrap_content"?? ????????????android:layout_marginTop="8dp"?? ????????????android:text="神奇動物城，法師顯超能"?? ????????????android:textColor="#99000000"?? ????????????android:textSize="11sp" />?? ?? ????????<TextView?? ????????????android:id="@+id/mv_date"?? ????????????android:layout_width="wrap_content"?? ????????????android:layout_height="wrap_content"?? ????????????android:layout_marginTop="10dp"?? ????????????android:text="今天165家影院放映2088場"?? ????????????android:textColor="#99000000"?? ????????????android:textSize="11sp" />?? ????</LinearLayout>?? ?? </LinearLayout>

第五步：一定不能忘！！！

recycleView不僅要設置適配器還要設置布局管理者,否則圖片不顯示

Java

1 2	GridLayoutManager manager = new GridLayoutManager(this, 1);?? ????????????recyclerView.setLayoutManager(manager);

此時RecyclerView簡單的完成效果如下：

下面開始做 可推動的 懸浮導航欄：

第一步：首先我們來寫一個類，它起標記的作用，來放每一個item的對應的懸浮欄的字符串

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public class NameBean {?? ????String name;?? ?? ????public String getName() {?? ????????return name;?? ????}?? ?? ????public void setName(String name) {?? ????????this.name = name;?? ????}?? }

第二步：自定義一個SectionDecoration 類?繼承 RecyclerView的ItemDecoration

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public class SectionDecoration extends RecyclerView.ItemDecoration {?? ????private static final String TAG = "SectionDecoration";?? ?? ????private List<NameBean> dataList;?? ?? ????private DecorationCallback callback;?? ????private TextPaint textPaint;?? ????private Paint paint;?? ????private int topGap;?? ????private int alignBottom;?? ????private Paint.FontMetrics fontMetrics;?? ?? ?? ????public SectionDecoration(List<NameBean> dataList, Context context, DecorationCallback decorationCallback) {?? ????????Resources res = context.getResources();?? ????????this.dataList = dataList;?? ????????this.callback = decorationCallback;?? ????????//設置懸浮欄的畫筆---paint?? ????????paint = new Paint();?? ????????paint.setColor(res.getColor(R.color.colorGray));?? ?? ????????//設置懸浮欄中文本的畫筆?? ????????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();?? ????????//決定懸浮欄的高度等?? ????????topGap = res.getDimensionPixelSize(R.dimen.sectioned_top);?? ????????//決定文本的顯示位置等?? ????????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;?? ????????//只有是同一組的第一個才顯示懸浮欄?? ????????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();?? ????????????????????//繪制懸浮欄?? ????????????????????c.drawRect(left, top - topGap, right, bottom, paint);?? ????????????????????//繪制文本?? ????????????????????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());?? ????????????//下一個和當前不一樣移動當前?? ????????????if (position + 1 < itemCount) {?? ????????????????String nextGroupId = callback.getGroupId(position + 1);?? ????????????????//組內最后一個view進入了header?? ????????????????if (nextGroupId != groupId && viewBottom < textY) {?? ????????????????????textY = viewBottom;?? ????????????????}?? ????????????}?? ????????????//textY - topGap決定了懸浮欄繪制的高度和位置?? ????????????c.drawRect(left, textY - topGap, right, textY, paint);?? ????????????//left+2*alignBottom 決定了文本往左偏移的多少（加-->向左移）?? ????????????//textY-alignBottom??決定了文本往右偏移的多少??(減-->向上移)?? ????????????c.drawText(textLine, left + 2 * alignBottom, textY - alignBottom, textPaint);?? ????????}?? ????}?? ?? ?? ????/** ???? * 判斷是不是組中的第一個位置 ???? * ???? * @param pos ???? * @return ???? */?? ????private boolean isFirstInGroup(int pos) {?? ????????if (pos == 0) {?? ????????????return true;?? ????????} else {?? ????????????// 因為是根據 字符串內容的相同與否 來判斷是不是同意組的，所以此處的標記id 要是String類型?? ????????????// 如果你只是做聯系人列表，懸浮框里顯示的只是一個字母，則標記id直接用 int 類型就行了?? ????????????String prevGroupId = callback.getGroupId(pos - 1);?? ????????????String groupId = callback.getGroupId(pos);?? ????????????//判斷前一個字符串 與 當前字符串 是否相同?? ????????????if (prevGroupId.equals(groupId)) {?? ????????????????return false;?? ????????????} else {?? ????????????????return true;?? ????????????}?? ????????}?? ????}?? ?? ????//定義一個借口方便外界的調用?? ????interface DecorationCallback {?? ????????String getGroupId(int position);?? ?? ????????String getGroupFirstLine(int position);?? ????}?? }

第三步：在向list集合中先把每一個item的 起“標記”作用的字符串都加進去

Java

1	setPullAction(comingslist);

?

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private void setPullAction(List<WaitMVBean.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，為RecyclerView添加ItemDecoration:

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recyclerView.addItemDecoration(new SectionDecoration(dataList,mContext, new SectionDecoration.DecorationCallback() {?? ?????????????? //返回標記id (即每一項對應的標志性的字符串)?? ????????????????@Override?? ????????????????public String getGroupId(int position) {?? ????????????????????if(dataList.get(position).getName()!=null) {?? ????????????????????????return dataList.get(position).getName();?? ????????????????????}?? ????????????????????return "-1";?? ????????????????}?? ?? ????????????????//獲取同組中的第一個內容?? ????????????????@Override?? ????????????????public String getGroupFirstLine(int position) {?? ????????????????????if(dataList.get(position).getName()!=null) {?? ????????????????????????return dataList.get(position).getName();?? ????????????????????}?? ????????????????????return "";?? ????????????????}?? ????????????}));

這樣就完成了~

再看一眼最終效果感受一下：

轉載于:https://www.cnblogs.com/henkun010/p/6645616.html

總結

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