diff --git a/app/src/main/java/net/micode/notes/ui/DateTimePicker.java b/app/src/main/java/net/micode/notes/ui/DateTimePicker.java
index 496b0cd..182690a 100644
--- a/app/src/main/java/net/micode/notes/ui/DateTimePicker.java
+++ b/app/src/main/java/net/micode/notes/ui/DateTimePicker.java
@@ -28,10 +28,18 @@ import android.view.View;
 import android.widget.FrameLayout;
 import android.widget.NumberPicker;
 
+/**
+ * 日期选择器，是 [FrameLayout] 的子类
+ */
 public class DateTimePicker extends FrameLayout {
 
     private static final boolean DEFAULT_ENABLE_STATE = true;
 
+    /**
+     * 常量声明，包含一些数值范围等
+     * 例如小时可选范围为0~23小时
+     * 分钟可选范围为0~59分钟
+      */
     private static final int HOURS_IN_HALF_DAY = 12;
     private static final int HOURS_IN_ALL_DAY = 24;
     private static final int DAYS_IN_ALL_WEEK = 7;
@@ -46,25 +54,59 @@ public class DateTimePicker extends FrameLayout {
     private static final int AMPM_SPINNER_MIN_VAL = 0;
     private static final int AMPM_SPINNER_MAX_VAL = 1;
 
+    /**
+     * 天数选择器
+      */
     private final NumberPicker mDateSpinner;
+    /**
+     * 时间选择器
+      */
     private final NumberPicker mHourSpinner;
+    /**
+     * 分钟选择器
+      */
     private final NumberPicker mMinuteSpinner;
+    /**
+     * AM / PM 早晚选择器
+      */
     private final NumberPicker mAmPmSpinner;
+    /**
+     * 日期实例对象
+      */
     private Calendar mDate;
-
+    /**
+     * 日期显示的数值
+     */
     private String[] mDateDisplayValues = new String[DAYS_IN_ALL_WEEK];
-
+    /**
+     * 是否是早晨
+      */
     private boolean mIsAm;
-
+    /**
+     * 是否是24小时制
+      */
     private boolean mIs24HourView;
-
+    /**
+     * 是否启用
+      */
     private boolean mIsEnabled = DEFAULT_ENABLE_STATE;
-
+    /**
+     * 是否正在初始化中
+      */
     private boolean mInitialising;
-
+    /**
+     * 日期变更监听器
+     */
     private OnDateTimeChangedListener mOnDateTimeChangedListener;
-
-    private NumberPicker.OnValueChangeListener mOnDateChangedListener = new NumberPicker.OnValueChangeListener() {
+    /**
+     * 数值改变监听器
+     *
+     * 在数值更改时同步修改 mDate 的数值
+     * 并刷新选择器的数值
+     * 触发时间改变监听器
+     */
+    private NumberPicker.OnValueChangeListener mOnDateChangedListener =
+            new NumberPicker.OnValueChangeListener() {
         @Override
         public void onValueChange(NumberPicker picker, int oldVal, int newVal) {
             mDate.add(Calendar.DAY_OF_YEAR, newVal - oldVal);
@@ -72,8 +114,13 @@ public class DateTimePicker extends FrameLayout {
             onDateTimeChanged();
         }
     };
-
-    private NumberPicker.OnValueChangeListener mOnHourChangedListener = new NumberPicker.OnValueChangeListener() {
+    /**
+     * 数值改变监听器
+     *
+     * 在数值改变时传入选择器对象和操作前与操作后的数值
+     * 对数值进行具体的分析
+     */
+    private NumberPicker.OnValueChangeListener mOnHourChangedListener = new NumberPicker.OnValueChangeListener(){
         @Override
         public void onValueChange(NumberPicker picker, int oldVal, int newVal) {
             boolean isDateChanged = false;
@@ -114,7 +161,9 @@ public class DateTimePicker extends FrameLayout {
             }
         }
     };
-
+    /**
+     * 分钟改变监听器
+     */
     private NumberPicker.OnValueChangeListener mOnMinuteChangedListener = new NumberPicker.OnValueChangeListener() {
         @Override
         public void onValueChange(NumberPicker picker, int oldVal, int newVal) {
@@ -143,7 +192,10 @@ public class DateTimePicker extends FrameLayout {
             onDateTimeChanged();
         }
     };
-
+    /**
+     * 早晚变更的监听器
+     * 在选择AM / PM的时候通知监听器触发方法
+     */
     private NumberPicker.OnValueChangeListener mOnAmPmChangedListener = new NumberPicker.OnValueChangeListener() {
         @Override
         public void onValueChange(NumberPicker picker, int oldVal, int newVal) {
@@ -185,7 +237,7 @@ public class DateTimePicker extends FrameLayout {
 
         mHourSpinner = (NumberPicker) findViewById(R.id.hour);
         mHourSpinner.setOnValueChangedListener(mOnHourChangedListener);
-        mMinuteSpinner =  (NumberPicker) findViewById(R.id.minute);
+        mMinuteSpinner = (NumberPicker) findViewById(R.id.minute);
         mMinuteSpinner.setMinValue(MINUT_SPINNER_MIN_VAL);
         mMinuteSpinner.setMaxValue(MINUT_SPINNER_MAX_VAL);
         mMinuteSpinner.setOnLongPressUpdateInterval(100);
@@ -475,11 +527,19 @@ public class DateTimePicker extends FrameLayout {
     public void setOnDateTimeChangedListener(OnDateTimeChangedListener callback) {
         mOnDateTimeChangedListener = callback;
     }
-
+    /**
+     * 在日期时间改变时调用该方法
+     * 如果日期时间改变监听器为空则不处理
+     * 不为空则调用监听器的方法
+     */
     private void onDateTimeChanged() {
-        if (mOnDateTimeChangedListener != null) {
-            mOnDateTimeChangedListener.onDateTimeChanged(this, getCurrentYear(),
-                    getCurrentMonth(), getCurrentDay(), getCurrentHourOfDay(), getCurrentMinute());
-        }
+        if (mOnDateTimeChangedListener == null) return;
+        mOnDateTimeChangedListener.onDateTimeChanged(this,
+                getCurrentYear(),
+                getCurrentMonth(),
+                getCurrentDay(),
+                getCurrentHourOfDay(),
+                getCurrentMinute()
+        );
     }
 }