1.毫秒设置成1000,实际上获取出来的时间是下个月的1号0点，改为999，防止出现其他月份；2. 滑动日历时，添加对月份变化的监听

CalendarPicker/src/main/java/com/github/gzuliyujiang/calendarpicker/CalendarPicker.java

@@ -29,6 +29,8 @@
 import com.github.gzuliyujiang.calendarpicker.core.FestivalProvider;
 import com.github.gzuliyujiang.calendarpicker.core.ItemViewProvider;
 import com.github.gzuliyujiang.calendarpicker.core.OnDateSelectedListener;
+import com.github.gzuliyujiang.calendarpicker.listener.OnPageChangeCallback;
+import com.github.gzuliyujiang.calendarpicker.listener.ScrollEventAdapter;
 import com.github.gzuliyujiang.dialog.DialogConfig;
 import com.github.gzuliyujiang.dialog.DialogStyle;
 import com.github.gzuliyujiang.dialog.ModalDialog;
@@ -47,6 +49,7 @@
 public class CalendarPicker extends ModalDialog implements OnDateSelectedListener {
     private CalendarView calendarView;
     private CalendarAdapter calendarAdapter;
+    private ScrollEventAdapter mScrollEventAdapter;
     private ColorScheme colorScheme;
     private boolean singleMode = false;
     private FestivalProvider festivalProvider;
@@ -104,8 +107,26 @@ protected void initData() {
             maxCalendar.set(Calendar.DAY_OF_MONTH, DateUtils.maxDaysOfMonth(maxCalendar.getTime()));
             maxDate = maxCalendar.getTime();
         }
+        if (mScrollEventAdapter == null) {
+            mScrollEventAdapter = new ScrollEventAdapter(calendarView.getBodyView());
+            calendarView.getBodyView().addOnScrollListener(mScrollEventAdapter);
+        }
         calendarAdapter = calendarView.getAdapter();
         calendarAdapter.setOnCalendarSelectedListener(this);
+        mScrollEventAdapter.setOnPageChangeCallback(new OnPageChangeCallback() {
+            @Override
+            public void onPageSelected(int position) {
+                if (calendarAdapter != null) {
+                    Date cDate = calendarAdapter.getDateValue(position);
+                    if (onSingleDatePickListener != null) {
+                        onSingleDatePickListener.onMonthChanged(cDate);
+                    }
+                    if (onRangeDatePickListener != null) {
+                        onRangeDatePickListener.onMonthChanged(cDate);
+                    }
+                }
+            }
+        });
         refreshData();
     }
 
@@ -331,4 +352,14 @@ public final CalendarView getCalendarView() {
         return calendarView;
     }
 
+    @Override
+    public void onDetachedFromWindow() {
+        super.onDetachedFromWindow();
+        if (mScrollEventAdapter != null && calendarView != null) {
+            mScrollEventAdapter.setOnPageChangeCallback(null);
+            calendarView.getBodyView().removeOnScrollListener(mScrollEventAdapter);
+            mScrollEventAdapter = null;
+        }
+    }
+
 }

CalendarPicker/src/main/java/com/github/gzuliyujiang/calendarpicker/OnRangeDatePickListener.java

@@ -25,4 +25,6 @@ public interface OnRangeDatePickListener {
 
     void onRangeDatePicked(@NonNull Date startDate, @NonNull Date endDate);
 
+    void onMonthChanged(Date date);
+
 }

CalendarPicker/src/main/java/com/github/gzuliyujiang/calendarpicker/OnSingleDatePickListener.java

@@ -25,4 +25,6 @@ public interface OnSingleDatePickListener {
 
     void onSingleDatePicked(@NonNull Date date);
 
+    void onMonthChanged(Date date);
+
 }

CalendarPicker/src/main/java/com/github/gzuliyujiang/calendarpicker/core/CalendarAdapter.java

@@ -275,7 +275,7 @@ public final int getDatePosition(Date date) {
             maxDate.set(Calendar.HOUR_OF_DAY, 23);
             maxDate.set(Calendar.MINUTE, 59);
             maxDate.set(Calendar.SECOND, 59);
-            maxDate.set(Calendar.MILLISECOND, 1000);
+            maxDate.set(Calendar.MILLISECOND, 999);
             if (time >= minDate.getTime().getTime() && time <= maxDate.getTime().getTime()) {
                 return i;
             }

CalendarPicker/src/main/java/com/github/gzuliyujiang/calendarpicker/listener/OnPageChangeCallback.java

@@ -0,0 +1,35 @@
+package com.github.gzuliyujiang.calendarpicker.listener;
+
+import androidx.annotation.Px;
+
+public abstract class OnPageChangeCallback {
+    /**
+     * This method will be invoked when the current page is scrolled, either as part
+     * of a programmatically initiated smooth scroll or a user initiated touch scroll.
+     *
+     * @param position Position index of the first page currently being displayed.
+     *                 Page position+1 will be visible if positionOffset is nonzero.
+     * @param positionOffset Value from [0, 1) indicating the offset from the page at position.
+     * @param positionOffsetPixels Value in pixels indicating the offset from position.
+     */
+    public void onPageScrolled(int position, float positionOffset,
+                               @Px int positionOffsetPixels) {
+    }
+
+    /**
+     * This method will be invoked when a new page becomes selected. Animation is not
+     * necessarily complete.
+     *
+     * @param position Position index of the new selected page.
+     */
+    public void onPageSelected(int position) {
+    }
+
+    /**
+     * Called when the scroll state changes. Useful for discovering when the user begins
+     * dragging, when a fake drag is started, when the pager is automatically settling to the
+     * current page, or when it is fully stopped/idle. {@code state} can be one of {@link
+     */
+    public void onPageScrollStateChanged(int state) {
+    }
+}