Android 最流行的吸顶效果的实现及代码 _Android

青春须早为，岂能长少年。这篇文章主要讲述Android 最流行的吸顶效果的实现及代码相关的知识，希望能为你提供帮助。
开始逐渐领略到ItemDecoration的美~
今天让我使用 ItemDecoration 来完成可推动的悬浮导航栏的效果，最终实现的效果如下图：

文章图片

【Android 最流行的吸顶效果的实现及代码】具体实现步骤如下：
根据我前面的文章所讲的RecyclerView的基本使用，我们先来完成基本的recyclerView：
第一步：布局里写一个RecyclerView
第二步：实例化

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

第三步：获取所需的数据 (这里我们来个真实点的情景，去联网请求数据)

/** * 联网请求所需的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"; //联网获取数据 getDataFromNet(); /** * 使用okhttpUtils进行联网请求数据 */ 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", "联网失败" + e.getMessage()); }@Override public void onResponse(String response, int id) { Log.e("TAG", "联网成功==" + response); //联网成功后使用fastjson解析 processData(response); } }); }/** * 使用fastjson进行解析 * * @param json */ private void processData(String json) { //这里使用GsonFormat生成对应的bean类 JSONObject jsonObject = parseObject(json); String data = https://www.songbingjia.com/android/jsonObject.getString("data"); JSONObject dataObj = JSON.parseObject(data); String coming = dataObj.getString("coming"); List< WaitMVBean.DataBean.ComingBean> comingslist = parseArray(coming, WaitMVBean.DataBean.ComingBean.class); //测试是否解析数据成功 //String strTest = comingslist.get(0).getCat(); //Log.e("TAG", strTest + "222"); //解析数据成功,设置适配器--> }}

第四步：解析数据成功后，创建并设置适配器,并传递相关数据

//解析数据成功,设置适配器 MyRecyclerAdapter adapter = new MyRecyclerAdapter( mContext,comingslist); recyclerView.setAdapter(adapter);

适配器：

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：当你发下图片无法打开是，做个字符串替换即可 String imagUrl = coming.getImg(); String newImagUrl = imagUrl.replaceAll("w.h", "50.80"); //使用Glide加载图片 Glide.with(mContext) .load(newImagUrl) .into(imageView); } } }

item的布局：

< ?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="观众" 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=" | 专业" 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场" android:textColor="#99000000" android:textSize="11sp" /> < /LinearLayout> < /LinearLayout>

第五步：一定不能忘！！！
recycleView不仅要设置适配器还要设置布局管理者,否则图片不显示

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

此时RecyclerView简单的完成效果如下：

文章图片

下面开始做可推动的悬浮导航栏：
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; } }

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; //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(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，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：