Android 最流行的吸頂效果的實現及代碼

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：布局裡寫一個RecyclerView

第二步：實例化

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

第三步：獲取所需的數據 (這裡我們來個真實點的情景，去聯網請求數據)

/** 
    * 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";

//聯網獲取數據  
       getDataFromNet();

/** 
     * 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);  

                        //聯網成功後使用fastjson解析  
                        processData(response);  
                    }  
                });  
    }

/** 
     * 使用fastjson進行解析 
     * 
     * @param json 
     */  
    private void processData(String json) {  
        //這裡使用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：解析數據成功後，創建並設置適配器,並傳遞相關數據

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

適配器：

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：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：

<?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

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

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

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);  
                //組內最後一個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，懸浮框裡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

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，為RecyclerView添加ItemDecoration:

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：