前言

RecyclerView 是 Android 中非常受欢迎的控件，谷歌官方在 Android5.0 之后新添加的控件，用以替代传统的 ListView 和 GridView 列表控件，适用于大数据展示，相对于传统的 ListView， RecyclerView 的效率更高，更加强大而灵活，这里简单说一下二者的区别

1 布局

ListView：布局单一，只支持竖直方向滑动，而 RecyclerView 支持多种布局 线性布局，实现横向纵向列表方向的 item， 网格布局，指定 item 的数替代 GridView 。瀑布流布局，指定列表方向，以及同方向的item数量

2 刷新

ListView 中通常刷新数据 notifyDataSetChanged() ，即全局刷新，每个 item的数据都会重新加载，资源消耗较大,当然 ListView 也可以实现局部刷新而 RecyclerView 可以通过 notifyItemChanged() 来实现局部刷新效率更高

3 ViewHolder

ListView 中 VewHolder 需要自定义，需要用 getview 去获取控件，则每次调用 getview 都要通过 findViewById 去获取控件，如果控件个数过多，会严重影响性能，因为findViewById相对比较耗时，所以我们需要创建自定义 ViewHolder，通过getTag 和 setTag 直接获取 view 而 RecyclerView 继承 RecyclerView .ViewHolder，默认需要重写 RecyclerView ，已经封装好

4 缓存机制

ListView 仅支持二级缓存，即通过两级缓存View，而 RecyclerView 有四级缓存可支持自定义缓存，具体区请自行度娘

正文

先看效果，即实现一个自定义的食谱列表横向包括星期，竖向包括早中晚三餐以及相应食谱列表展示

首先先导入RecyclerView 与 Gson 解析依赖包

    implementation 'androidx.recyclerview:recyclerview:1.1.0-beta01'implementation 'com.google.code.gson:gson:2.2.2'

再其次就是需要用到的数据，这里我首先新建个 assets 资源文件夹如图

assets 创建方法如图

紧接着就是创建资源数据在 assets 文件夹下创建一个data.json 用来存放数据资源直接右键 new File 文件名以 .json 结尾即可

{"status": "Y","msg": "获取成功","data": [{"week": "星期一","dinner": [{"dinnername": "早点","list": [{"DishName": "包子"},{"DishName": "窝窝头"},{"DishName": "白面膜"}]},{"dinnername": "午点","list": [{"DishName": "栗子"},{"DishName": "苹果"},{"DishName": "西瓜"}]},{"dinnername": "晚餐","list": [{"DishName": "鸡蛋灌饼"},{"DishName": "烤冷面"}]},{"dinnername": "早餐","list": [{"DishName": "花生米"},{"DishName": "白开水"},{"DishName": "西蓝花"}]},{"dinnername": "午餐","list": [{"DishName": "西红柿鸡蛋"},{"DishName": "宫爆鸡丁"},{"DishName": "火爆猪心"}]}]},{"week": "星期二","dinner": [{"dinnername": "早点","list": [{"DishName": "纯牛奶"},{"DishName": "酸奶"},{"DishName": "优酸乳"}]},{"dinnername": "午点","list": [{"DishName": "杨桃"},{"DishName": "玉米"}]},{"dinnername": "晚餐","list": [{"DishName": "酸辣粉"},{"DishName": "麻辣烫"}]},{"dinnername": "早餐","list": [{"DishName": "蔬菜粥"},{"DishName": "玉米粥"},{"DishName": "包子"}]},{"dinnername": "午餐","list": [{"DishName": "鲜虾丸子"},{"DishName": "麻婆豆腐"}]}]},{"week": "星期三","dinner": [{"dinnername": "早点","list": [{"DishName": "仙魔奶昔"},{"DishName": "奶酪"},{"DishName": "红薯"}]},{"dinnername": "午点","list": [{"DishName": "火龙果"}]},{"dinnername": "晚餐","list": [{"DishName": "兰州拉面"}]},{"dinnername": "早餐","list": [{"DishName": "八宝粥"},{"DishName": "小花卷"}]},{"dinnername": "午餐","list": [{"DishName": "清蒸鲤鱼"},{"DishName": "水煮肉片"}]}]},{"week": "星期四","dinner": [{"dinnername": "早点","list": [{"DishName": "绿豆饼"}]},{"dinnername": "午点","list": [{"DishName": "海苔"}]},{"dinnername": "晚餐","list": []},{"dinnername": "早餐","list": [{"DishName": "燕麦粥"}]},{"dinnername": "午餐","list": [{"DishName": "娃娃菜"},{"DishName": "猪心肉"}]}]},{"week": "星期五","dinner": [{"dinnername": "早点","list": [{"DishName": "豆浆"}]},{"dinnername": "午点","list": [{"DishName": "干煸鸡翅"}]},{"dinnername": "晚餐","list": [{"DishName": "杀猪菜"}]},{"dinnername": "早餐","list": [{"DishName": "西红柿鸡蛋面"}]},{"dinnername": "午餐","list": [{"DishName": "炒豆芽"}]}]},{"week": "星期六","dinner": [{"dinnername": "早点","list": [{"DishName": "包子"}]},{"dinnername": "午点","list": [{"DishName": "娃娃菜"}]},{"dinnername": "晚餐","list": [{"DishName": "西瓜饼"}]},{"dinnername": "早餐","list": [{"DishName": "油条"}]},{"dinnername": "午餐","list": [{"DishName": "驴肉火烧"}]}]},{"week": "星期日","dinner": [{"dinnername": "早点","list": [{"DishName": "冰镇西瓜"}]},{"dinnername": "午点","list": [{"DishName": "扒肉"}]},{"dinnername": "晚餐","list": []},{"dinnername": "早餐","list": [{"DishName": "小笼包"}]},{"dinnername": "午餐","list": [{"DishName": "大鸡腿"}]}]}]
}

然后就需要创建实体类 FootBean 实现 Parcelable ，Parcelable 是安卓专用的序列化接口，这里不得不先提一下 Serializable 接口，Serializable 是 Java 为我们提供的一个标准化的序列化接口，使用简单，实现即可，而 Parcelable 是 Android 为我们提供的序列化的接口，Parcelable 相对于Serializable 的使用相对复杂一些,重写3个方法

createFromParcel(Parcelparcel) writeToParcel(Parcel parcel) newArray(int size)

但 Parcelable 的效率相对 Serializable 也高很多，这里多说一嘴解释下什么是序列化，序列化是将对象的状态信息转换为可以存储或传输的形式的过程。在序列化期间，对象将其当前状态写入到 Ram 或者是 rom，也就是临时或持久性存储区。以后，可以通过从存储区中读取对象的状态，重新创建该对象，这个就是反序列化。言归正题由于接口比较复杂我这里用可视化工具展示下以遍大家理解

层次嵌套有点多，每一层的List 都要实现 Parcelable

public class FootBean implements Parcelable {/*** status : Y* msg : 获取成功* data : [{"week":"星期一","dinner":[{"dinnername":"早点","list":[{"DishName":"包子"},{"DishName":"窝窝头"},{"DishName":"白面膜"}]},{"dinnername":"午点","list":[{"DishName":"栗子"},{"DishName":"苹果"},{"DishName":"西瓜"}]},{"dinnername":"晚餐","list":[{"DishName":"鸡蛋灌饼"},{"DishName":"烤冷面"}]},{"dinnername":"早餐","list":[{"DishName":"花生米"},{"DishName":"白开水"},{"DishName":"西蓝花"}]},{"dinnername":"午餐","list":[{"DishName":"西红柿鸡蛋"},{"DishName":"宫爆鸡丁"},{"DishName":"火爆猪心"}]}]},{"week":"星期二","dinner":[{"dinnername":"早点","list":[{"DishName":"纯牛奶"},{"DishName":"酸奶"},{"DishName":"优酸乳"}]},{"dinnername":"午点","list":[{"DishName":"杨桃"},{"DishName":"玉米"}]},{"dinnername":"晚餐","list":[{"DishName":"酸辣粉"},{"DishName":"麻辣烫"}]},{"dinnername":"早餐","list":[{"DishName":"蔬菜粥"},{"DishName":"玉米粥"},{"DishName":"包子"}]},{"dinnername":"午餐","list":[{"DishName":"鲜虾丸子"},{"DishName":"麻婆豆腐"}]}]},{"week":"星期三","dinner":[{"dinnername":"早点","list":[{"DishName":"仙魔奶昔"},{"DishName":"奶酪"},{"DishName":"红薯"}]},{"dinnername":"午点","list":[{"DishName":"火龙果"}]},{"dinnername":"晚餐","list":[{"DishName":"兰州拉面"}]},{"dinnername":"早餐","list":[{"DishName":"八宝粥"},{"DishName":"小花卷"}]},{"dinnername":"午餐","list":[{"DishName":"清蒸鲤鱼"},{"DishName":"水煮肉片"}]}]},{"week":"星期四","dinner":[{"dinnername":"早点","list":[{"DishName":"绿豆饼"}]},{"dinnername":"午点","list":[{"DishName":"海苔"}]},{"dinnername":"晚餐","list":[]},{"dinnername":"早餐","list":[{"DishName":"燕麦粥"}]},{"dinnername":"午餐","list":[{"DishName":"娃娃菜"},{"DishName":"猪心肉"}]}]},{"week":"星期五","dinner":[{"dinnername":"早点","list":[{"DishName":"豆浆"}]},{"dinnername":"午点","list":[{"DishName":"干煸鸡翅"}]},{"dinnername":"晚餐","list":[{"DishName":"杀猪菜"}]},{"dinnername":"早餐","list":[{"DishName":"西红柿鸡蛋面"}]},{"dinnername":"午餐","list":[{"DishName":"炒豆芽"}]}]},{"week":"星期六","dinner":[{"dinnername":"早点","list":[{"DishName":"包子"}]},{"dinnername":"午点","list":[{"DishName":"娃娃菜"}]},{"dinnername":"晚餐","list":[{"DishName":"西瓜饼"}]},{"dinnername":"早餐","list":[{"DishName":"油条"}]},{"dinnername":"午餐","list":[{"DishName":"驴肉火烧"}]}]},{"week":"星期日","dinner":[{"dinnername":"早点","list":[{"DishName":"冰镇西瓜"}]},{"dinnername":"午点","list":[{"DishName":"扒肉"}]},{"dinnername":"晚餐","list":[]},{"dinnername":"早餐","list":[{"DishName":"小笼包"}]},{"dinnername":"午餐","list":[{"DishName":"大鸡腿"}]}]}]*/private String status;private String msg;private List<DataBean> data;@Overridepublic String toString() {return "FootBean{" +"status='" + status + '\'' +", msg='" + msg + '\'' +", data=" + data +'}';}protected FootBean(Parcel in) {status = in.readString();msg = in.readString();}public static final Creator<FootBean> CREATOR = new Creator<FootBean>() {@Overridepublic FootBean createFromParcel(Parcel in) {return new FootBean(in);}@Overridepublic FootBean[] newArray(int size) {return new FootBean[size];}};public String getStatus() {return status;}public void setStatus(String status) {this.status = status;}public String getMsg() {return msg;}public void setMsg(String msg) {this.msg = msg;}public List<DataBean> getData() {return data;}public void setData(List<DataBean> data) {this.data = data;}@Overridepublic int describeContents() {return 0;}@Overridepublic void writeToParcel(Parcel dest, int flags) {dest.writeString(status);dest.writeString(msg);}public static class DataBean implements Parcelable {/*** week : 星期一* dinner : [{"dinnername":"早点","list":[{"DishName":"包子"},{"DishName":"窝窝头"},{"DishName":"白面膜"}]},{"dinnername":"午点","list":[{"DishName":"栗子"},{"DishName":"苹果"},{"DishName":"西瓜"}]},{"dinnername":"晚餐","list":[{"DishName":"鸡蛋灌饼"},{"DishName":"烤冷面"}]},{"dinnername":"早餐","list":[{"DishName":"花生米"},{"DishName":"白开水"},{"DishName":"西蓝花"}]},{"dinnername":"午餐","list":[{"DishName":"西红柿鸡蛋"},{"DishName":"宫爆鸡丁"},{"DishName":"火爆猪心"}]}]*/private String week;private List<DinnerBean> dinner;@Overridepublic String toString() {return "DataBean{" +"week='" + week + '\'' +", dinner=" + dinner +'}';}protected DataBean(Parcel in) {week = in.readString();}public static final Creator<DataBean> CREATOR = new Creator<DataBean>() {@Overridepublic DataBean createFromParcel(Parcel in) {return new DataBean(in);}@Overridepublic DataBean[] newArray(int size) {return new DataBean[size];}};public String getWeek() {return week;}public void setWeek(String week) {this.week = week;}public List<DinnerBean> getDinner() {return dinner;}public void setDinner(List<DinnerBean> dinner) {this.dinner = dinner;}@Overridepublic int describeContents() {return 0;}@Overridepublic void writeToParcel(Parcel dest, int flags) {dest.writeString(week);}public static class DinnerBean implements Parcelable {/*** dinnername : 早点* list : [{"DishName":"包子"},{"DishName":"窝窝头"},{"DishName":"白面膜"}]*/private String dinnername;private List<ListBean> list;@Overridepublic String toString() {return "DinnerBean{" +"dinnername='" + dinnername + '\'' +", list=" + list +'}';}protected DinnerBean(Parcel in) {dinnername = in.readString();}public static final Creator<DinnerBean> CREATOR = new Creator<DinnerBean>() {@Overridepublic DinnerBean createFromParcel(Parcel in) {return new DinnerBean(in);}@Overridepublic DinnerBean[] newArray(int size) {return new DinnerBean[size];}};public String getDinnername() {return dinnername;}public void setDinnername(String dinnername) {this.dinnername = dinnername;}public List<ListBean> getList() {return list;}public void setList(List<ListBean> list) {this.list = list;}@Overridepublic int describeContents() {return 0;}@Overridepublic void writeToParcel(Parcel dest, int flags) {dest.writeString(dinnername);}public static class ListBean implements Parcelable {/*** DishName : 包子*/private String DishName;@Overridepublic String toString() {return "ListBean{" +"DishName='" + DishName + '\'' +'}';}protected ListBean(Parcel in) {DishName = in.readString();}public static final Creator<ListBean> CREATOR = new Creator<ListBean>() {@Overridepublic ListBean createFromParcel(Parcel in) {return new ListBean(in);}@Overridepublic ListBean[] newArray(int size) {return new ListBean[size];}};public String getDishName() {return DishName;}public void setDishName(String DishName) {this.DishName = DishName;}@Overridepublic int describeContents() {return 0;}@Overridepublic void writeToParcel(Parcel dest, int flags) {dest.writeString(DishName);}}}}
}

接下来就是给 RecyclerView 添加自定义分割线新建一个 DividerItemDecoration 类继承RecyclerView.ItemDecoration

public class DividerItemDecoration extends RecyclerView.ItemDecoration {private Paint mPaint;//取名mDivider似乎更恰当private Drawable mDrawable;//分割线高度，默认为1pxprivate int mDividerHeight = 2;//列表的方向private int mOrientation;//系统自带的参数private static final int[] ATTRS = new int[]{android.R.attr.listDivider};//水平public static final int HORIZONTAL_LIST = RecyclerView.HORIZONTAL;//垂直public static final int VERTICAL_LIST = RecyclerView.VERTICAL;//水平+垂直public static final int BOTH_SET = 2;/*** 默认分割线：高度为2px，颜色为灰色** @param context     上下文* @param orientation 列表方向*/public DividerItemDecoration(Context context, int orientation) {this.setOrientation(orientation);//获取xml配置的参数final TypedArray a = context.obtainStyledAttributes(ATTRS);//typedArray.getDrawable(attr)这句是说我们可以通过我们的资源获得资源，使用我们的资源名attr去获得资源id//看不懂就用自己写一个分割线的图片吧，方法：ContextCompat.getDrawable(context, drawableId);mDrawable = a.getDrawable(0);//官方的解释是：回收TypedArray，以便后面重用。在调用这个函数后，你就不能再使用这个TypedArray。//在TypedArray后调用recycle主要是为了缓存。a.recycle();}/*** 自定义分割线** @param context     上下文* @param orientation 列表方向* @param drawableId  分割线图片*/public DividerItemDecoration(Context context, int orientation, int drawableId) {this.setOrientation(orientation);//旧的getDrawable方法弃用了，这个是新的mDrawable = ContextCompat.getDrawable(context, drawableId);mDividerHeight = mDrawable.getIntrinsicHeight();}/*** 自定义分割线** @param context       上下文* @param orientation   列表方向* @param dividerHeight 分割线高度* @param dividerColor  分割线颜色*/public DividerItemDecoration(Context context, int orientation, int dividerHeight, int dividerColor) {this.setOrientation(orientation);mDividerHeight = dividerHeight;Log.e("mDividerHeight", mDividerHeight + "===================");//抗锯齿画笔mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);mPaint.setColor(dividerColor);//填满颜色mPaint.setStyle(Paint.Style.FILL);}/*** 设置方向** @param orientation*/public void setOrientation(int orientation) {if (orientation < 0 || orientation > 2)throw new IllegalArgumentException("invalid orientation");mOrientation = orientation;}/*** 绘制分割线之后,需要留出一个外边框,就是说item之间的间距要换一下** @param outRect outRect.set(0, 0, 0, 0);的四个参数理解成margin就好了* @param view    视图* @param parent  父级view* @param state*/@Overridepublic void getItemOffsets(@NonNull Rect outRect, @NonNull View view, @NonNull RecyclerView parent, @NonNull RecyclerView.State state) {//下面super...代码其实调用的就是那个过时的getItemOffsets,也就是说这个方法体内容也可以通通移到那个过时的getItemOffsets中super.getItemOffsets(outRect, view, parent, state);//获取layoutParams参数RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams) view.getLayoutParams();//当前位置int itemPosition = layoutParams.getViewLayoutPosition();//ItemView数量int childCount = parent.getAdapter().getItemCount();switch (mOrientation) {case BOTH_SET://获取Layout的相关参数int spanCount = this.getSpanCount(parent);if (isLastRaw(parent, itemPosition, spanCount, childCount)) {// 如果是最后一行，则不需要绘制底部outRect.set(0, 0, mDividerHeight, 0);} else if (isLastColum(parent, itemPosition, spanCount, childCount)) {// 如果是最后一列，则不需要绘制右边outRect.set(0, 0, 0, mDividerHeight);} else {outRect.set(0, 0, mDividerHeight, mDividerHeight);}break;case VERTICAL_LIST:childCount -= 1;//水平布局右侧留Margin,如果是最后一列,就不要留Margin了outRect.set(0, 0, (itemPosition != childCount) ? mDividerHeight : 0, 0);break;case HORIZONTAL_LIST:childCount -= 1;//垂直布局底部留边，最后一行不留outRect.set(0, 0, 0, (itemPosition != childCount) ? mDividerHeight : 0);break;}}/*** 绘制分割线** @param c* @param parent* @param state*/@Overridepublic void onDraw(@NonNull Canvas c, @NonNull RecyclerView parent, @NonNull RecyclerView.State state) {super.onDraw(c, parent, state);if (mOrientation == VERTICAL_LIST) {drawVertical(c, parent);} else if (mOrientation == HORIZONTAL_LIST) {drawHorizontal(c, parent);} else {drawHorizontal(c, parent);drawVertical(c, parent);}}/*** 绘制横向 item 分割线** @param canvas 画布* @param parent 父容器*/private void drawHorizontal(Canvas canvas, RecyclerView parent) {final int x = parent.getPaddingLeft();final int width = parent.getMeasuredWidth() - parent.getPaddingRight();//getChildCount()(ViewGroup.getChildCount) 返回的是显示层面上的“所包含的子 View 个数”。final int childSize = parent.getChildCount();for (int i = 0; i < childSize; i++) {final View child = parent.getChildAt(i);RecyclerView.LayoutParams layoutParams =(RecyclerView.LayoutParams) child.getLayoutParams();//item底部的Y轴坐标+margin值final int y = child.getBottom() + layoutParams.bottomMargin;final int height = y + mDividerHeight;Log.e("height", height + "===================");if (mDrawable != null) {//setBounds(x,y,width,height); x:组件在容器X轴上的起点 y:组件在容器Y轴上的起点// width:组件的长度 height:组件的高度mDrawable.setBounds(x, y, width, height);mDrawable.draw(canvas);}if (mPaint != null) {canvas.drawRect(x, y, width, height, mPaint);}}}/*** 绘制纵向 item 分割线** @param canvas* @param parent*/private void drawVertical(Canvas canvas, RecyclerView parent) {final int top = parent.getPaddingTop();final int bottom = parent.getMeasuredHeight() - parent.getPaddingBottom();final int childSize = parent.getChildCount();for (int i = 0; i < childSize; i++) {final View child = parent.getChildAt(i);RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams) child.getLayoutParams();final int left = child.getRight() + layoutParams.rightMargin;final int right = left + mDividerHeight;if (mDrawable != null) {mDrawable.setBounds(left, top, right, bottom);mDrawable.draw(canvas);}if (mPaint != null) {canvas.drawRect(left, top, right, bottom, mPaint);}}}/*** 获取列数** @param parent* @return*/private int getSpanCount(RecyclerView parent) {int spanCount = -1;RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();if (layoutManager instanceof GridLayoutManager) {spanCount = ((GridLayoutManager) layoutManager).getSpanCount();} else if (layoutManager instanceof StaggeredGridLayoutManager) {spanCount = ((StaggeredGridLayoutManager) layoutManager).getSpanCount();}return spanCount;}private boolean isLastColum(RecyclerView parent, int pos, int spanCount,int childCount) {RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();if (layoutManager instanceof GridLayoutManager) {int orientation = ((GridLayoutManager) layoutManager).getOrientation();if (orientation == StaggeredGridLayoutManager.VERTICAL) {// 如果是最后一列，则不需要绘制右边return (pos + 1) % spanCount == 0;} else {childCount = childCount - childCount % spanCount;// 如果是最后一列，则不需要绘制右边return pos >= childCount;}} else if (layoutManager instanceof StaggeredGridLayoutManager) {int orientation = ((StaggeredGridLayoutManager) layoutManager).getOrientation();if (orientation == StaggeredGridLayoutManager.VERTICAL) {// 如果是最后一列，则不需要绘制右边return (pos + 1) % spanCount == 0;} else {childCount = childCount - childCount % spanCount;// 如果是最后一列，则不需要绘制右边return pos >= childCount;}}return false;}private boolean isLastRaw(RecyclerView parent, int pos, int spanCount, int childCount) {int orientation;RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();if (layoutManager instanceof GridLayoutManager) {childCount = childCount - childCount % spanCount;orientation = ((GridLayoutManager) layoutManager).getOrientation();if (orientation == StaggeredGridLayoutManager.VERTICAL) {// 如果是最后一行，则不需要绘制底部childCount = childCount - childCount % spanCount;if (pos >= childCount)return true;} else {// StaggeredGridLayoutManager 横向滚动// 如果是最后一行，则不需要绘制底部if ((pos + 1) % spanCount == 0)return true;}} else if (layoutManager instanceof StaggeredGridLayoutManager) {orientation = ((StaggeredGridLayoutManager) layoutManager).getOrientation();if (orientation == StaggeredGridLayoutManager.VERTICAL) {// 如果是最后一行，则不需要绘制底部childCount = childCount - childCount % spanCount;if (pos >= childCount)return true;} else {// StaggeredGridLayoutManager 横向滚动// 如果是最后一行，则不需要绘制底部if ((pos + 1) % spanCount == 0)return true;}}return false;}
}

这里还需要一个工具类用来引用资源文件下的内容新建一个Utils类

public class Utils {public static String getFromAssets(Context context, String fileName) {InputStreamReader inputReader = null;BufferedReader bufReader = null;try {inputReader = new InputStreamReader(context.getResources().getAssets().open(fileName));bufReader = new BufferedReader(inputReader);String line = "";StringBuilder result = new StringBuilder();while ((line = bufReader.readLine()) != null)result.append(line);return result.toString();} catch (Exception e) {e.printStackTrace();} finally {try {if (inputReader != null) {inputReader.close();}if (bufReader != null) {bufReader.close();}} catch (IOException e) {e.printStackTrace();}}return "";}
}

列表是少不了适配器的新建一个FootAdapter继RecyclerView.Adapter<RecyclerView.ViewHolder>

public class FootAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {private List<String> mDataList = new ArrayList<>();public FootAdapter(List<String> dataList) {this.mDataList = dataList;}@NonNull@Overridepublic RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {return new ViewHolder(LayoutInflater.from(parent.getContext()).inflate(R.layout.item_recycler_layout, parent, false));}@Overridepublic void onBindViewHolder(@NonNull RecyclerView.ViewHolder holder, int position) {if (holder instanceof ViewHolder) {((ViewHolder) holder).textView.setText(mDataList.get(position));}}@Overridepublic int getItemCount() {return mDataList.size();}private static class ViewHolder extends RecyclerView.ViewHolder {TextView textView;public ViewHolder(@NonNull View itemView) {super(itemView);textView = itemView.findViewById(R.id.item_title);}}
}

布局文件也简单就一个TextView

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:app="http://schemas.android.com/apk/res-auto"android:layout_width="match_parent"android:layout_height="wrap_content"><TextViewandroid:id="@+id/item_title"android:layout_width="match_parent"android:layout_height="wrap_content"android:gravity="center"android:minHeight="60dp"app:layout_constraintStart_toStartOf="parent"app:layout_constraintTop_toTopOf="parent" /></androidx.constraintlayout.widget.ConstraintLayout>

最后就是MainActivity了布局文件

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:app="http://schemas.android.com/apk/res-auto"xmlns:tools="http://schemas.android.com/tools"android:layout_width="match_parent"android:layout_height="match_parent"android:layout_margin="5dp"tools:context=".MainActivity"><androidx.recyclerview.widget.RecyclerViewandroid:id="@+id/recycler_view"android:layout_width="match_parent"android:layout_height="wrap_content"android:background="@drawable/bg_recycer"android:overScrollMode="never"app:layout_constraintStart_toStartOf="parent"app:layout_constraintTop_toTopOf="parent" /></androidx.constraintlayout.widget.ConstraintLayout>

这里主要就是定义 7 个 List，其中mDataList为整体List ，mWeeks用以加载星期展示，其余的就是列表展开下的餐段以及熟普信息具体参考上述 Json可视化展示图片，然后通络循环数据列表依次加载到相应的List 上

public class MainActivity extends AppCompatActivity {private static final String TAG = "Demo-MainActivity";private List<String> mBreakfastList1 = new ArrayList<>();private List<String> mBreakfastList2 = new ArrayList<>();private List<String> mLunch1 = new ArrayList<>();private List<String> mLunch2 = new ArrayList<>();private List<String> mDinner = new ArrayList<>();private List<String> mWeeks = new ArrayList<>();private List<String> mDataList = new ArrayList<>();private RecyclerView mRecyclerView;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);String data = Utils.getFromAssets(this, "data.json");getDataList(data);mDataList.addAll(mWeeks);mDataList.add("早餐");mDataList.addAll(mBreakfastList1);mDataList.add("早点");mDataList.addAll(mBreakfastList2);mDataList.add("午餐");mDataList.addAll(mLunch1);mDataList.add("午点");mDataList.addAll(mLunch1);mDataList.add("晚餐");mDataList.addAll(mDinner);mRecyclerView = findViewById(R.id.recycler_view);mRecyclerView.setLayoutManager(new GridLayoutManager(this, mWeeks.size()));mRecyclerView.setHasFixedSize(true);mRecyclerView.addItemDecoration(new DividerItemDecoration(this, DividerItemDecoration.BOTH_SET, 3, getColor(R.color.colorAccent)));FootAdapter adapter = new FootAdapter(mDataList);mRecyclerView.setAdapter(adapter);}private void getDataList(String data) {FootBean bean = new Gson().fromJson(data, FootBean.class);Log.d(TAG, "bean = " + bean.toString());mWeeks.add("");for (FootBean.DataBean dataBean : bean.getData()) {
//            if (dataBean.getWeek().equals("星期六") || dataBean.getWeek().equals("星期日")) {
//                return;
//            }mWeeks.add(dataBean.getWeek());for (FootBean.DataBean.DinnerBean dinnerBean : dataBean.getDinner()) {if (dinnerBean.getDinnername().equals("早餐")) {StringBuilder sb = new StringBuilder();for (int i = 0; i < dinnerBean.getList().size(); i++) {sb.append(dinnerBean.getList().get(i).getDishName());if (i != dinnerBean.getList().size() - 1) {sb.append("\n");}}mBreakfastList1.add(sb.toString());}if (dinnerBean.getDinnername().equals("早点")) {StringBuilder sb = new StringBuilder();for (int i = 0; i < dinnerBean.getList().size(); i++) {sb.append(dinnerBean.getList().get(i).getDishName());if (i != dinnerBean.getList().size() - 1) {sb.append("\n");}}mBreakfastList2.add(sb.toString());}if (dinnerBean.getDinnername().equals("午餐")) {StringBuilder sb = new StringBuilder();for (int i = 0; i < dinnerBean.getList().size(); i++) {sb.append(dinnerBean.getList().get(i).getDishName());if (i != dinnerBean.getList().size() - 1) {sb.append("\n");}}mLunch1.add(sb.toString());}if (dinnerBean.getDinnername().equals("午点")) {StringBuilder sb = new StringBuilder();for (int i = 0; i < dinnerBean.getList().size(); i++) {sb.append(dinnerBean.getList().get(i).getDishName());if (i != dinnerBean.getList().size() - 1) {sb.append("\n");}}mLunch2.add(sb.toString());}if (dinnerBean.getDinnername().equals("晚餐")) {StringBuilder sb = new StringBuilder();for (int i = 0; i < dinnerBean.getList().size(); i++) {sb.append(dinnerBean.getList().get(i).getDishName());if (i != dinnerBean.getList().size() - 1) {sb.append("\n");}}mDinner.add(sb.toString());}}}}
}

源码后续会上传，有什么问题评论区留言，第一时间回复。

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