Click on the calendar to select a date (the accounting calendar currently has additions and subtractions)

Calendar (the accounting calendar currently has additions and subtractions)

1. Entity class

public class CalendarBean {
    //0：当月，1：上月，2：下一个月
    private int dayType;

    //星期
    private String weekOfDay;

    //日期
    private String day;

    //实际日期
    private Date date;

    public Date getDate() {
        return date;
    }

    public void setDate(Date date) {
        this.date = date;
    }

    public int getDayType() {
        return dayType;
    }

    public void setDayType(int dayType) {
        this.dayType = dayType;
    }

    public String getWeekOfDay() {
        return weekOfDay == null ? "" : weekOfDay;
    }

    public void setWeekOfDay(String weekOfDay) {
        this.weekOfDay = weekOfDay == null ? "" : weekOfDay;
    }

    public String getDay() {
        return day == null ? "" : day;
    }

    public void setDay(String day) {
        this.day = day == null ? "" : day;
    }
}

2. Adapter

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;

import java.util.ArrayList;
import java.util.List;

public abstract class BaseRecycerAdapter<T> extends RecyclerView.Adapter<ViewHolder> {

    private List<T> mData;
    private Context mContext;
    private int mResId;

    private OnItemClickListener<T> mItemClickListener;
    private OnItemLongClickListener<T> mItemLongClickListener;

    public BaseRecycerAdapter(Context context, List<T> datas, int resId) {
        this.mContext = context;
        this.mData = datas;
        this.mResId = resId;
    }

    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {

        View itemView = LayoutInflater.from(mContext).inflate(mResId, viewGroup, false);
        return new ViewHolder(itemView);
    }

    @Override
    public final void onBindViewHolder(@NonNull ViewHolder viewHolder, final int i) {

        final T t = mData.get(i);
        onBindViewHolder(viewHolder, t, i);
        viewHolder.getRootView().setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (mItemClickListener != null) {
                    mItemClickListener.onItemClick(t, i);
                }
            }
        });

        viewHolder.getRootView().setOnLongClickListener(new View.OnLongClickListener() {
            @Override
            public boolean onLongClick(View view) {
                if (mItemLongClickListener != null) {
                    mItemLongClickListener.onItemLongClickListener(t, i);
                }
                return false;
            }
        });
    }

    @Override
    public int getItemCount() {
        if (mData != null && mData.size() > 0) {
            return mData.size();
        }
        return 0;
    }

    /**
     * @param viewHolder
     * @param itemVO
     * @param position
     */
    public abstract void onBindViewHolder(ViewHolder viewHolder, T itemVO, int position);

    public interface OnItemClickListener<T> {
        void onItemClick(T t, int position);
    }

    public interface OnItemLongClickListener<T> {
        void onItemLongClickListener(T t, int position);
    }

    public BaseRecycerAdapter setOnItemClickListener(OnItemClickListener listener) {
        if (listener != null) {
            this.mItemClickListener = listener;
        }
        return this;
    }

    public BaseRecycerAdapter setOnItemLongClickListener(OnItemLongClickListener listener) {
        this.mItemLongClickListener = listener;
        return this;
    }

    public List<T> getData() {
        if (mData == null) {
            mData = new ArrayList<>();
        }
        return mData;
    }

    public void setData(List<T> mData) {
        this.mData = mData;
    }
}

3. Adapter

import android.text.TextUtils;
import android.util.SparseArray;
import android.view.View;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;

public class ViewHolder extends RecyclerView.ViewHolder {

    private SparseArray<View> mViews;
    private View mRootView;

    public ViewHolder(@NonNull View itemView) {
        super(itemView);
        this.mRootView = itemView;
        mViews = new SparseArray<>();
    }

    //获取view
    public <T extends View> T findViewById(int id) {
        View view = mViews.get(id);
        if (view == null) {
            view = itemView.findViewById(id);
            mViews.put(id, view);
        }
        return (T) view;
    }

    public View getRootView() {
        return mRootView;
    }

    /**
     * 直接设置TextView的内容，仅限TextView及它的子类使用
     *
     * @param id   需要设置View的ID
     * @param text 需要设置的内容
     * @return
     */
    public ViewHolder setText(int id, String text) {
        if (!TextUtils.isEmpty(text) && id != 0) {
            View view = findViewById(id);
            if (view instanceof TextView) {
                ((TextView) view).setText(text);
            }
        }
        return this;
    }
}

4. Customized calendar view

public class CustomCalendarView extends FrameLayout {

    protected float FLIP_DISTANCE;

    private SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM");

    private RecyclerView listView;
    private ArrayList<CalendarBean> mDatas = new ArrayList<>();
    private BaseRecycerAdapter mAdapter;

    //当前显示月份
    private CalendarBean mCurrentMonthCalendar;

    public CustomCalendarView(@NonNull Context context) {
        super(context);
        init(context, null);
    }

    public CustomCalendarView(@NonNull Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        init(context, attrs);
    }

    public CustomCalendarView(@NonNull Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init(context, attrs);
    }

    private void init(Context context, AttributeSet attrs) {
        FLIP_DISTANCE = ViewConfiguration.get(context).getScaledTouchSlop();
        View view = LayoutInflater.from(context).inflate(R.layout.view_calendar, this);
        listView = view.findViewById(R.id.list_date);

        initAdapter();

        initData(null);

        listView.setLayoutManager(new GridLayoutManager(context, 7));
        listView.setAdapter(mAdapter);

    }

    private float downX;
    private float downY;

    @Override
    public boolean dispatchTouchEvent(MotionEvent event) {
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                downX = event.getX();
                downY = event.getY();
                break;
            case MotionEvent.ACTION_MOVE:
                break;
            case MotionEvent.ACTION_UP:
                float upX = event.getX();
                float upY = event.getY();

                float suduY = Math.abs(downY - upY);
                if (upX - downX > suduY && upX - downX > FLIP_DISTANCE) {
                    goLastMonth();
                }

                if (downX - upX > suduY && downX - upX > FLIP_DISTANCE) {
                    goNextMonth();
                }
                break;
        }
        return super.dispatchTouchEvent(event);
    }

    private void initAdapter() {
        mAdapter = new BaseRecycerAdapter<CalendarBean>(getContext(), mDatas, R.layout.item_scheduling_day) {
            @Override
            public void onBindViewHolder(ViewHolder viewHolder, CalendarBean itemVO, int position) {
                TextView tv_day = viewHolder.findViewById(R.id.tv_day);
                ConstraintLayout cl_calendar_selection = viewHolder.findViewById(R.id.cl_calendar_selection);
//                TextView tv_state = viewHolder.findViewById(R.id.tv_state);
                tv_day.setText(itemVO.getDay());
//点击切换
                if (itemVO.getCheck()) {
                    cl_calendar_selection.setBackground(getContext().getDrawable(R.drawable.calendar_selection));
                } else {
                    cl_calendar_selection.setBackground(getContext().getDrawable(R.color.white));
                }

                if (itemVO.getDayType() == 1) {
                    //上个月数据
                    tv_day.setTextColor(getResources().getColor(R.color.color_999999));
                    viewHolder.getRootView().setBackgroundColor(getResources().getColor(R.color.color_ffffff));
//                    tv_state.setVisibility(INVISIBLE);
                } else {
                    viewHolder.getRootView().setBackgroundColor(getResources().getColor(R.color.color_ffffff));
                    tv_day.setTextColor(getResources().getColor(R.color.color_434343));
//                    tv_state.setVisibility(VISIBLE);
                }
            }
        };
    }


    /**
     * 初始化时间
     *
     * @param indexDate yyyy-MM-dd
     */
    private void initData(CalendarBean indexDate) {

        Calendar instance = Calendar.getInstance();

        if (indexDate != null) {
            //自定月份
            instance.setTime(indexDate.getDate());
        }

        //获取当前月最大的日期
        int maxDate = instance.getActualMaximum(Calendar.DATE);
        instance.set(Calendar.DAY_OF_MONTH, 1);
        //获取当前月所有的天数
        for (int i = 0; i < maxDate; i++, instance.add(Calendar.DATE, 1)) {
            int day = instance.get(Calendar.DAY_OF_MONTH);
            CalendarBean calendarBean = new CalendarBean();
            calendarBean.setDay(String.valueOf(day));
            calendarBean.setDate(instance.getTime());
            mDatas.add(calendarBean);
        }

        //赋值当前月份
        mCurrentMonthCalendar = mDatas.get(0);

        String format = simpleDateFormat.format(mCurrentMonthCalendar.getDate());
        String[] split = format.split("-");

        Date date = new Date();
        instance.setTime(date);
        instance.add(Calendar.DATE, 0);
        Date time = instance.getTime();
        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");
        String format1 = simpleDateFormat.format(time);
        String[] split1 = format1.split("-");
        String s = split1[2];
        int i = Integer.parseInt(s);

        for (CalendarBean mData : mDatas) {
            int i1 = Integer.parseInt(mData.getDay());
            //当前时间
            if (split[0].equals(split1[0]) && split[1].equals(split1[1]) && i1 == i) {
                mData.setCheck(true);
            }
        }
        //点击传入给适配器
        mAdapter.setOnItemClickListener(new BaseRecycerAdapter.OnItemClickListener() {
            @Override
            public void onItemClick(Object o, int position) {
                for (CalendarBean mData : mDatas) {
                    mData.setCheck(false);
                }
                mDatas.get(position).setCheck(true);
                mAdapter.notifyDataSetChanged();
            }
        });

        ArrayList<CalendarBean> calendarBeans = processDay(mDatas);
        mDatas.clear();
        mDatas.addAll(calendarBeans);

        mAdapter.notifyDataSetChanged();
    }

    /**
     * 获取当前月份
     *
     * @return
     */
    public String getMonth() {
        return simpleDateFormat.format(mCurrentMonthCalendar.getDate());
    }

    /**
     * 显示下一个月
     */
    public void goNextMonth() {
        String lastMonth = simpleDateFormat.format(mCurrentMonthCalendar.getDate());
        Calendar instance = Calendar.getInstance();
        instance.setTime(mCurrentMonthCalendar.getDate());
        instance.add(Calendar.MONTH, 1);
        CalendarBean tempBean = new CalendarBean();
        tempBean.setDate(instance.getTime());

        mDatas.clear();
        initData(tempBean);
        String newMonth = simpleDateFormat.format(tempBean.getDate());
        if (listener != null) {
            listener.onMonthChanger(lastMonth, newMonth);
        }
    }

    /**
     * 显示上一个月
     */
    public void goLastMonth() {
        String lastMonth = simpleDateFormat.format(mCurrentMonthCalendar.getDate());
        Calendar instance = Calendar.getInstance();
        instance.setTime(mCurrentMonthCalendar.getDate());
        instance.add(Calendar.MONTH, -1);
        CalendarBean tempBean = new CalendarBean();
        tempBean.setDate(instance.getTime());

        mDatas.clear();
        initData(tempBean);
        String newMonth = simpleDateFormat.format(tempBean.getDate());
        if (listener != null) {
            listener.onMonthChanger(lastMonth, newMonth);
        }
    }


    /**
     * 拼接上一个月数据和下一个月数据
     *
     * @param signDatas
     * @return
     */
    private ArrayList<CalendarBean> processDay(ArrayList<CalendarBean> signDatas) {

        ArrayList<CalendarBean> list = new ArrayList<>();

        //获取上一个月需要补全的天数
        ArrayList<CalendarBean> lastMonth = getLastMonth(signDatas.get(0));

        //获取下一个月需要补全的天数
        ArrayList<CalendarBean> nextMonth = getNextMonth(signDatas.get(0));

        if (lastMonth != null && lastMonth.size() > 0) {
            //如果有上一个月的天数，进行添加
            list.addAll(lastMonth);
        }

        if (signDatas != null) {
            //当前月天数
            list.addAll(signDatas);
        }

        if (nextMonth != null && nextMonth.size() > 0) {
            //如果有下一个月的天数，进行添加
            list.addAll(nextMonth);
        }
        return list;
    }

    /**
     * 获取上一个月需要补全的天数
     *
     * @return
     */
    private ArrayList<CalendarBean> getLastMonth(CalendarBean calendarBean) {
        //获取当前月第一天
        Calendar calendarFirstDay = Calendar.getInstance();
        calendarFirstDay.setTime(calendarBean.getDate());
        calendarFirstDay.set(Calendar.DAY_OF_MONTH, 1);
        //当月第一天是星期几
        int firstDayOfWeek = calendarFirstDay.get(Calendar.DAY_OF_WEEK);
        if (firstDayOfWeek != 1) {
            /**
             *   firstDayOfWeek =1时，就是星期日，当前月第一天已经处于星期日，不需要添加上一个月补充天数
             */
            //需要补全的天数，当needAdd为负数时候，说明是星期日，需要补6天
            int needAdd = firstDayOfWeek - 1;

            ArrayList<CalendarBean> lastMonth = new ArrayList<>();
            for (int i = 0; i < needAdd; i++) {
                CalendarBean dayBean = new CalendarBean();
                //0：当月，1：上月，2：下一个月
                dayBean.setDayType(1);
                dayBean.setWeekOfDay(getWeekString(i));
                //取出上一个月需要补全的天数
                //calendarFirstDay.set(Calendar.DAY_OF_MONTH, 0 - i);
                calendarFirstDay.add(Calendar.DATE, -1);
                //上一个月的天数
                int lastMonthDay = calendarFirstDay.get(Calendar.DAY_OF_MONTH);
                dayBean.setDay(String.valueOf(lastMonthDay));
                dayBean.setDate(dayBean.getDate());
                lastMonth.add(0, dayBean);
            }

            return lastMonth;

        }
        return new ArrayList<>();
    }

    /**
     * 获取下一个月需要补全的天数
     *
     * @return
     */
    private ArrayList<CalendarBean> getNextMonth(CalendarBean calendarBean) {

        //获取当前月最后一天
        Calendar calendarLastDay = Calendar.getInstance();
        calendarLastDay.setTime(calendarBean.getDate());
        calendarLastDay.add(Calendar.MONTH, 1);
        calendarLastDay.set(Calendar.DAY_OF_MONTH, 0);
        //获取当前月最后一天是星期几
        int nextDayOfWeek = calendarLastDay.get(Calendar.DAY_OF_WEEK);
        if (nextDayOfWeek != 7) {
            /**
             *   nextDayOfWeek =7时，就是星期六，当前月最后一天已经处于星期六，不需要添加上一个月补充天数
             */
            int needAdd = 7 - nextDayOfWeek;

            ArrayList<CalendarBean> nextMonth = new ArrayList<>();
            for (int i = 1; i <= needAdd; i++) {
                CalendarBean dayBean = new CalendarBean();
                //0：当月，1：上月，2：下一个月
                dayBean.setDayType(2);
                dayBean.setWeekOfDay(getWeekString(i));
                //取出上一个月需要补全的天数
                calendarLastDay.set(Calendar.DAY_OF_MONTH, i);
                //上一个月的天数
                int lastMonthDay = calendarLastDay.get(Calendar.DAY_OF_MONTH);
                dayBean.setDay(String.valueOf(lastMonthDay));
                dayBean.setDate(dayBean.getDate());
                nextMonth.add(dayBean);
            }
            return nextMonth;
        }
        return new ArrayList<>();
    }

    private String getWeekString(int i) {
        switch (i) {
            case 1:
                return "星期日";
            case 2:
                return "星期一";
            case 3:
                return "星期二";
            case 4:
                return "星期三";
            case 5:
                return "星期四";
            case 6:
                return "星期五";
            case 7:
                return "星期六";
            default:
                return "超出范围";
        }
    }

    private OnMonthChangerListener listener;

    public void setOnMonthChangerListener(OnMonthChangerListener listener) {
        this.listener = listener;
    }

    public interface OnMonthChangerListener {
        void onMonthChanger(String lastMonth, String newMonth);
    }
}

5. Items in the adapter

<?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="55dp"
    android:layout_height="68dp">

    <androidx.constraintlayout.widget.ConstraintLayout
        android:id="@+id/cl_calendar_selection"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <TextView
            android:id="@+id/tv_day"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="15dp"
            android:text="21"
            android:textColor="#434343"
            android:textSize="13sp"
            android:textStyle="bold"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

        <androidx.appcompat.widget.AppCompatTextView
            android:id="@+id/appCompatTextView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="3dp"
            android:text="+200.00"
            android:textColor="#FF7D7E"
            android:textSize="12sp"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toBottomOf="@id/tv_day" />

        <androidx.appcompat.widget.AppCompatTextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="-0.00"
            android:textColor="#3ED1AE"
            android:textSize="12sp"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/appCompatTextView" />

    </androidx.constraintlayout.widget.ConstraintLayout>

</androidx.constraintlayout.widget.ConstraintLayout>

6. Customize the xml in the view

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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="wrap_content"
    android:orientation="vertical">

    <LinearLayout
        android:id="@+id/ll_week"
        android:layout_width="match_parent"
        android:layout_height="33dp"
        android:orientation="horizontal"
        app:layout_constraintLeft_toLeftOf="parent">

        <TextView
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:gravity="center"
            android:text="日"
            android:textColor="#999999"
            android:textSize="14dp" />

        <TextView
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:gravity="center"
            android:text="一"
            android:textColor="#999999"
            android:textSize="14dp" />

        <TextView
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:gravity="center"
            android:text="二"
            android:textColor="#999999"
            android:textSize="14dp" />

        <TextView
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:gravity="center"
            android:text="三"
            android:textColor="#999999"
            android:textSize="14dp" />

        <TextView
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:gravity="center"
            android:text="四"
            android:textColor="#999999"
            android:textSize="14dp" />

        <TextView
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:gravity="center"
            android:text="五"
            android:textColor="#999999"
            android:textSize="14dp" />

        <TextView
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:gravity="center"
            android:text="六"
            android:textColor="#999999"
            android:textSize="14dp" />

    </LinearLayout>

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/list_date"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@drawable/bud_get_goal_bg"
        tools:itemCount="31"
        tools:layoutManager="androidx.recyclerview.widget.GridLayoutManager"
        tools:listitem="@layout/item_scheduling_day"
        tools:spanCount="7" />

</LinearLayout>

7. xml of activity and fragment

    <?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:background="#F4F4F6"
    android:orientation="vertical"
    tools:context=".activity.BillingCalendarActivity">

    <androidx.constraintlayout.widget.ConstraintLayout
        android:id="@+id/constraintLayout8"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="19dp"
        app:layout_constraintTop_toTopOf="parent">

        <androidx.appcompat.widget.AppCompatImageView
            android:id="@+id/iv_billing_calendar_finish"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginStart="19dp"
            android:src="@drawable/ic_back_dt"
            app:layout_constraintBottom_toBottomOf="@+id/tv_date"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="@+id/tv_date" />

        <androidx.appcompat.widget.AppCompatImageView
            android:id="@+id/iv_billing_add"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginEnd="19dp"
            android:src="@drawable/billing_add_img"
            app:layout_constraintBottom_toBottomOf="@+id/tv_date"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintTop_toTopOf="@+id/tv_date" />

        <View
            android:id="@+id/view_line1"
            android:layout_width="0dp"
            android:layout_height="10dp"
            android:background="#F6F6F6"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

        <TextView
            android:id="@+id/tv_date"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="21dp"
            android:text="2020-05"
            android:textColor="#171717"
            android:textSize="18sp"
            android:textStyle="bold"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toBottomOf="@id/view_line1" />

        <ImageView
            android:id="@+id/iv_last_month"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:padding="21dp"
            android:src="@drawable/ic_arrow_left"
            app:layout_constraintBottom_toBottomOf="@id/tv_date"
            app:layout_constraintRight_toLeftOf="@id/tv_date"
            app:layout_constraintTop_toTopOf="@id/tv_date" />

        <ImageView
            android:id="@+id/iv_next_month"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:padding="21dp"
            android:src="@drawable/ic_arrow_right"
            app:layout_constraintBottom_toBottomOf="@id/tv_date"
            app:layout_constraintLeft_toRightOf="@id/tv_date"
            app:layout_constraintTop_toTopOf="@id/tv_date" />

        <View
            android:id="@+id/view_line2"
            android:layout_width="0dp"
            android:layout_height="0.5dp"
            android:background="#EDEDED"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintTop_toBottomOf="@id/iv_next_month" />

        <com.example.bookkeeping.widget.CustomCalendarView
            android:id="@+id/calendarView"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_marginStart="12dp"
            android:layout_marginEnd="12dp"
            android:background="@drawable/bud_get_goal_bg"
            app:layout_constraintTop_toBottomOf="@id/view_line2" />

    </androidx.constraintlayout.widget.ConstraintLayout>

</androidx.constraintlayout.widget.ConstraintLayout>

8. In activity or fragment

iv_billing_calendar_finish.setOnClickListener {
            finish()
        }

        //更改title的年和月
        val month = calendarView!!.month
        tv_date!!.text = month

        iv_last_month.setOnClickListener { //上一个月
            calendarView!!.goLastMonth()
        }
        iv_next_month.setOnClickListener { //下一个月
            calendarView!!.goNextMonth()
        }

        //更改title的年和月
        calendarView.setOnMonthChangerListener(CustomCalendarView.OnMonthChangerListener { lastMonth, newMonth ->
            tv_date.text = newMonth
        })