diff --git a/src/小米便签代码精读.txt b/src/小米便签代码精读.txt
new file mode 100644
index 0000000..0c30135
--- /dev/null
+++ b/src/小米便签代码精读.txt
@@ -0,0 +1,1122 @@
+package net.micode.notes.data;
+
+import android.content.Context;
+import android.database.Cursor;
+import android.provider.ContactsContract.CommonDataKinds.Phone;
+import android.provider.ContactsContract.Data;
+import android.telephony.PhoneNumberUtils;
+import android.util.Log;
+
+import java.util.HashMap;
+
+public class Contact {
+    private static HashMap<String, String> sContactCache;
+//用于构建查询联系人的条件语句
+    private static final String TAG = "Contact";
+
+    private static final String CALLER_ID_SELECTION = "PHONE_NUMBERS_EQUAL(" + Phone.NUMBER
+    + ",?) AND " + Data.MIMETYPE + "='" + Phone.CONTENT_ITEM_TYPE + "'"
+    + " AND " + Data.RAW_CONTACT_ID + " IN "
+            + "(SELECT raw_contact_id "
+            + " FROM phone_lookup"
+            + " WHERE min_match = '+')";
+
+    public static String getContact(Context context, String phoneNumber) {
+        if(sContactCache == null) {
+            sContactCache = new HashMap<String, String>();
+        }
+
+        if(sContactCache.containsKey(phoneNumber)) {
+            return sContactCache.get(phoneNumber);
+        }
+//这个条件语句使用了Android提供的一些常量和函数，用于查询电话号码相等且数据类型为电话的联系人信息。
+
+        String selection = CALLER_ID_SELECTION.replace("+",
+                PhoneNumberUtils.toCallerIDMinMatch(phoneNumber));
+//方法将电话号码中的"+"替换为最小匹配的呼叫者ID。
+        Cursor cursor = context.getContentResolver().query(
+                Data.CONTENT_URI,
+//查询联系人数据。
+                new String [] { Phone.DISPLAY_NAME },
+                selection,
+                new String[] { phoneNumber },
+                null);
+//表示查询条件，即根据电话号码进行匹配。
+        if (cursor != null && cursor.moveToFirst()) {
+            try {
+                String name = cursor.getString(0);
+                sContactCache.put(phoneNumber, name);
+                return name;
+            } catch (IndexOutOfBoundsException e) {
+                Log.e(TAG, " Cursor get string error " + e.toString());
+                return null;
+            } finally {
+                cursor.close();
+            }
+        } else {
+            Log.d(TAG, "No contact matched with number:" + phoneNumber);
+//表示查询条件中的参数，即要匹配的电话号码。
+            return null;
+        }
+    }
+}
+
+```java
+package net.micode.notes.data;
+
+import android.net.Uri;
+
+/**
+ * 此类表示与笔记相关的常量和数据结构。
+ */
+public class Notes {
+
+    // 内容提供程序的权限
+    public static final String AUTHORITY = "micode_notes";
+
+    // 用于记录日志的标签
+    public static final String TAG = "Notes";
+
+    // 表示不同类型笔记的常量
+    public static final int TYPE_NOTE     = 0;
+    public static final int TYPE_FOLDER   = 1;
+    public static final int TYPE_SYSTEM   = 2;
+
+    /**
+     * 以下是系统文件夹的标识符：
+     * {@link Notes#ID_ROOT_FOLDER} 是默认文件夹
+     * {@link Notes#ID_TEMPARAY_FOLDER} 用于不属于任何文件夹的笔记
+     * {@link Notes#ID_CALL_RECORD_FOLDER} 用于存储通话记录
+     * {@link Notes#ID_TRASH_FOLDER} 用于垃圾文件夹
+     */
+    public static final int ID_ROOT_FOLDER = 0;
+    public static final int ID_TEMPARAY_FOLDER = -1;
+    public static final int ID_CALL_RECORD_FOLDER = -2;
+    public static final int ID_TRASH_FOLDER = -3;
+
+    // Intent额外键
+    public static final String INTENT_EXTRA_ALERT_DATE = "net.micode.notes.alert_date";
+    public static final String INTENT_EXTRA_BACKGROUND_ID = "net.micode.notes.background_color_id";
+    public static final String INTENT_EXTRA_WIDGET_ID = "net.micode.notes.widget_id";
+    public static final String INTENT_EXTRA_WIDGET_TYPE = "net.micode.notes.widget_type";
+    public static final String INTENT_EXTRA_FOLDER_ID = "net.micode.notes.folder_id";
+    public static final String INTENT_EXTRA_CALL_DATE = "net.micode.notes.call_date";
+
+    // 表示不同类型小部件的常量
+    public static final int TYPE_WIDGET_INVALID = -1;
+    public static final int TYPE_WIDGET_2X = 0;
+    public static final int TYPE_WIDGET_4X = 1;
+
+    /**
+     * 包含数据类型常量的内部类。
+     */
+    public static class DataConstants {
+        // 不同笔记类型的内容项类型
+        public static final String NOTE = TextNote.CONTENT_ITEM_TYPE;
+        public static final String CALL_NOTE = CallNote.CONTENT_ITEM_TYPE;
+    }
+}
+```java
+/**
+ * 用于查询所有笔记和文件夹的 Uri
+ */
+public static final Uri CONTENT_NOTE_URI = Uri.parse("content://" + AUTHORITY + "/note");
+
+/**
+ * 用于查询数据的 Uri
+ */
+public static final Uri CONTENT_DATA_URI = Uri.parse("content://" + AUTHORITY + "/data");
+
+public interface NoteColumns {
+    /**
+     * 行的唯一 ID
+     * <P> 类型: INTEGER (long) </P>
+     */
+    public static final String ID = "_id";
+
+    /**
+     * 笔记或文件夹的父级 ID
+     * <P> 类型: INTEGER (long) </P>
+     */
+    public static final String PARENT_ID = "parent_id";
+
+    /**
+     * 笔记或文件夹的创建日期
+     * <P> 类型: INTEGER (long) </P>
+     */
+    public static final String CREATED_DATE = "created_date";
+
+    /**
+     * 最新修改日期
+     * <P> 类型: INTEGER (long) </P>
+     */
+    public static final String MODIFIED_DATE = "modified_date";
+
+
+    /**
+     * 提醒日期
+     * <P> 类型: INTEGER (long) </P>
+     */
+    public static final String ALERTED_DATE = "alert_date";
+
+    /**
+     * 文件夹名称或笔记的文本内容
+     * <P> 类型: TEXT </P>
+     */
+    public static final String SNIPPET = "snippet";
+
+    /**
+     * 笔记的小部件 ID
+     * <P> 类型: INTEGER (long) </P>
+     */
+    public static final String WIDGET_ID = "widget_id";
+
+    /**
+     * 笔记的小部件类型
+     * <P> 类型: INTEGER (long) </P>
+     */
+    public static final String WIDGET_TYPE = "widget_type";
+
+    /**
+     * 笔记的背景颜色 ID
+     * <P> 类型: INTEGER (long) </P>
+     */
+    public static final String BG_COLOR_ID = "bg_color_id";
+
+    /**
+     * 对于文本笔记，它没有附件，对于多媒体笔记，它至少有一个附件
+     * <P> 类型: INTEGER </P>
+     */
+    public static final String HAS_ATTACHMENT = "has_attachment";
+
+    /**
+     * 文件夹中笔记的计数
+     * <P> 类型: INTEGER (long) </P>
+     */
+    public static final String NOTES_COUNT = "notes_count";
+}
+
+```java
+/**
+ * 用于表示文本笔记的静态内部类
+ */
+public static final class TextNote implements DataColumns {
+    /**
+     * 指示文本是否处于待办事项模式的模式
+     * <P> 类型: Integer 1: 待办事项模式 0: 正常模式 </P>
+     */
+    public static final String MODE = DATA1;
+
+    public static final int MODE_CHECK_LIST = 1;
+
+    /**
+     * 内容类型为文本笔记的目录类型
+     */
+    public static final String CONTENT_TYPE = "vnd.android.cursor.dir/text_note";
+
+    /**
+     * 内容项类型为文本笔记的项目类型
+     */
+    public static final String CONTENT_ITEM_TYPE = "vnd.android.cursor.item/text_note";
+
+    /**
+     * 用于查询文本笔记的 Uri
+     */
+    public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY + "/text_note");
+}
+
+/**
+ * 用于表示通话记录的静态内部类
+ */
+public static final class CallNote implements DataColumns {
+    /**
+     * 此记录的通话日期
+     * <P> 类型: INTEGER (long) </P>
+     */
+    public static final String CALL_DATE = DATA1;
+
+    /**
+     * 此记录的电话号码
+     * <P> 类型: TEXT </P>
+     */
+    public static final String PHONE_NUMBER = DATA3;
+
+    /**
+     * 内容类型为通话记录的目录类型
+     */
+    public static final String CONTENT_TYPE = "vnd.android.cursor.dir/call_note";
+
+    /**
+     * 内容项类型为通话记录的项目类型
+     */
+    public static final String CONTENT_ITEM_TYPE = "vnd.android.cursor.item/call_note";
+
+    /**
+     * 用于查询通话记录的 Uri
+     */
+    public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY + "/call_note");
+}
+```
+
+
+package net.micode.notes.ui;
+import android.app.Activity;
+import android.app.AlertDialog;
+import android.content.Context;
+import android.content.DialogInterface;
+import android.content.Dialoginterface.OnClickListener;
+import android.content.DialogInterface.OnDismissListener;
+import android.content.Intent;
+import android.media.AudioManager;
+import android.media.MediaPlayer;
+import android.media.RingtoneManager;
+import android.net.Uri; import android.os.Bundle;
+import android.os.PowerManager;
+import android.provider.Settings;
+import android.view.Window;
+import android.view.WindowManager;
+import net.micode.notes.R:
+import net.micode.notes.data.Notes;
+import net.micode.notes.tool.DataUtils;
+import java.io.IOException;
+
+public class AlarmAlertActivity extends Activity implements OnClickListener, OnDismissListener { 
+	private long mNoteld;
+	//文本在数据库存储中的ID号 
+	private String mSnippet;
+	//闹钟提示时出现的文本片段 
+	private static final intSNIPPET_PREW_MAX_LEN=60;
+
+MediaPlayer mPlayer;
+
+@Override
+protected vold onCreate(Bundle savedInstanceState) { 
+	super.onCreate(savedInstanceState);
+//Bundle类型的数据与Map类型的数据相似，都是以key-value的形式存储数据的
+//onsavelnstanceState方法是用来保存Activity的状态的
+//能从 onCreate的参数savedInsanceState中获得状态数据 
+requestWindowFeature(Window.FEATURE_NO_TITLE);
+//界面显示一-无标题
+final Window win=getWindow();
+win.addFlags(WindowManager.LayoutParams.FLAG SHOW_WHEN LOCKED);
+if (lisScreenOn()){
+win.addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON
+//保持窗体点亮
+WindowManager.LayoutParams.FLAG_TURN_SCREEN_ON
+//将窗体点亮
+|WindowManager.LayoutParams.FLAG_ALLOW_LOCK_WHILE_SCREEN_ON
+//允许窗体点亮时锁屏
+WindowManager.LayoutParams.FLAG_LAYOUT_INSET_DECOR);]
+//在手机锁屏后如果到了闹钟提示时间，点亮屏幕
+Intent intent =getIntent();
+try{
+mNoteld=Long.valueOf(intent.getData().getPathSegments().get(1));
+mSnippet =DataUtils.getSnippetByld(this.getContentResolver(), mNoteld);
+//根据ID从数据库中获取标签的内容:
+//getContentResolver()是实现数据共享，实例存储。
+mSnippet = mSnippet.length() >SNIPPET_PREW_MAX_LEN ? mSnippet.substring(0,
+SNIPPET_PREW_MAX_LEN)+getResources().getString(R.string.notelist_string_info):mSnippet;
+//判断标签片段是否达到符合长度} catch (IllegalArgumentException e){ e.printStackTrace(); return;
+
+try
+// 代码区
+
+catch(Exception e)
+//异常处理
+代码区如果有错误，就会返回所写异常的处理。*/ mPlayer = new MediaPlayer();
+if (DataUtils,visibleInNoteDatabase(getContentResolver(), mNoteld, Notes.TYPE_NOTE)) { showActionDialog();
+试访	试读	
+//弹出对话框 playAlarmSound();//闹钟提示音激发}else{ finish();
+//完成闹钟动作
+
+private boolean isScreenOn(){
+//判断屏幕是否锁屏，调用系统函数判断
+PowerManager pm = (PowerManager) getSystemService(Context.POWER_SERVICE); return pm.isScreenOn();
+
+private vold playAlarmSound() {//闹钟提示音激发
+Uri	url	RingtoneManager.getActualDefaultRingtoneUri(this,	
+RingtoneManager.TYPE_ALARM);
+//调用系统的铃声管理URI，得到闹钟提示音
+int silentModeStreams =Settings.System.getInt(getContentResolver(),
+Settings.System.MODE_RINGER_STREAMS_AFFECTED,0);
+if ((silentModeStreams & (1<<AudioManager.STREAM_ALARM)) != 0) {
+mPlayer.setAudioStreamType(silentModeStreams);
+}else{
+mPlayer.setAudioStreamType(AudioManager.STREAM_ALARM);
+}
+try{
+mPlayer.setDataSource(this, url);
+//方法:setDataSource(Context context, Uri uri)
+//解释:无返回值，设置多媒体数据来源[根据Uni]
+mPlayer.prepare();
+//准备同步
+mPlayer.setLooping(true);
+//设置是否循环播放
+
+mPlayer.start();
+//开始播放
+} catch (IllegalArgumentException e) {
+// TODO Auto-generated catch block e.printStackTrace();
+//e.printStackTrace()函数功能是抛出异常，还将显示出更深的调用信息
+//System.out.printin(e)，这个方法打印出异常，并且输出在哪里出现的异常
+}catch (SecurityException e) {
+// TODO Auto-generated catch block 
+e.printStackTrace();
+} catch (IllegalStateException e)
+{
+// TODO Auto-generated catch block e.printStackTrace();} catch (I0Exception e)
+ {
+// TODO Auto-generated catch block e.printStackTrace();
+
+private void showActionDialog(){
+AlertDialog.Builder dialog = new AlertDialog.Builder(this);
+//AlertDialog的构造方法全部是Protected的
+//所以不能直接通过new一个AlertDialog来创建出一个AlertDialog。
+//要创建一个AlertDialog，就要用到AlertDialog.Builder中的create()方法
+
+//为对话框设置标题
+dialog.setMessage(mSnippet);
+//为对话框设置内容
+dialog.setPositiveButton(R.string.notealert_ok, this);
+//给对话框添加"Yes"按钮 if (isScreenOn()) {
+dialog.setNegativeButton(R.string.notealert_enter, this);}
+//对话框添加"No"按钮
+dialog.show().setOnDismissListener(this);
+
+public void onClick(Dialoginterface dialog, int which) { 
+switch (which) {
+//用which 来选择click后下一步的操作 case DialogInterface.BUTTON NEGATIVE:
+//这是取消操作
+Intent intent = new Intent(this, NoteEditActivity.class);
+//实现两个类间的数据传输
+
+MediaPlayer mPlayer;
+@Override
+protected void onCreate(Bundle savedInstanceState) { 
+super.onCreate(savedInstanceState);
+//Bundle 类型的数据与Map类型的数据相似，都是以key-value的形式存储数据的
+//onsavelnstanceState方法是用来保存Activity的状态的
+//能从onCreate的参数savedInsanceState中获得状态数据 requestWindowFeature(Window.FEATURE_NO_TITLE);
+//界面显示
+
+final Window win=getWindow();
+win.addFlags(WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED);
+if(!isScreenOn()){
+win.addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON
+
+//保持窗体点亮
+|WindowManager.LayoutParams.FLAG_TURN_SCREEN_ON
+//将窗体点亮
+|WindowManager.LayoutParams.FLAG_ALLOW_LOCK_WHILE_SCREEN_ON
+//允许窗体点亮时锁屏
+|WindowManager.LayoutParams.FLAG_LAYOUT_INSET_DECOR);}
+//在手机锁屏后如果到了闹钟提示时间，点亮屏幕
+Intent intent =getintent();
+try{
+
+mNoteld =Long.valueOf(intent.getData().getPathSegments().get(1));
+mSnippet = DataUtils.getSnippetByld(this.getContentResolver(),mNoteld);
+//根据ID从数据库中获取标签的内容;
+//getContentResolver()是实现数据共享，实例存储。
+mSnippet = mSnippet.length() >SNIPPET_PREW_MAX_LEN ? mSnippet.substring(0,
+SNIPPET_PREW_MAX_LEN) +getResources().getString(R.string.notelist_string_info):mSnippet;
+//判断标签片段是否达到符合长度} catch (IllegalArgumentException e){ e.printStackTrace(); return;
+/* try
+// 代码区
+catch(Exception e){
+//异常处理
+代码区如果有错误，就会返回所写异常的处理。*/ mPlayer = new MediaPlayer();
+if (DataUtils.visiblelnNoteDatabase(getContentResolver(), mNoteld, Notes.TYPE_NOTE)) { showActionDialog();
+//弹出对话框 playAlarmSound();
+//闹钟提示音激发
+
+} else{ finish();
+//完成闹钟动作
+
+private boolean isScreenOn(){
+//判断屏幕是否锁屏，调用系统函数判断，最后返回值是布尔类型
+PowerManager pm = (PowerManager) getSystemService(Context.POWER_SERVICE); return pm.isScreenOn();
+
+private void playAlarmSound() {
+//闹钟提示音激发
+Uri	url	RingtoneManager.getActualDefaultRingtoneUri(this,	
+RingtoneManager.TYPE_ALARM);
+//调用系统的铃声管理URI，得到闹钟提示音
+int silentModeStreams = Settings.System.getint(getContentResolver(),
+Settings.System.MODE_RINGER_STREAMS_AFFECTED, 0);
+if ((silentModeStreams & (1 << AudioManager.STREAM_ALARM)) != 0) { mPlayer.setAudioStreamType(silentModeStreams);}else{
+mPlayer.setAudioStreamType(AudioManager.STREAM_ALARM);
+try{
+mPlayer.setDataSource(this, url);
+//方法:setDataSource(Context context, Uri uri)
+//解释:无返回值，设置多媒体数据来源[根据Uni] mPlayer.prepare();
+//准备同步
+mPlayer.setLooping(true);//设置是否循环播放
+
+mPlayer.start();
+//开始播放
+} catch (IllegalArgumentException e) {
+// TODO Auto-generated catch block e.printStackTrace();
+
+// TODO Auto-generated catch block e.printStackTrace();
+}catch (IllegalStateException e){
+// TODO Auto-generated ctch block e.printStackTrace();} catch (IOException e) {
+// TODO Auto-generated catch block e.printStackTrace();
+
+private void showActionDialog(){
+AlertDialog,Builder dialog = new AlertDialog.Builder(this);
+//AlertDialog的构造方法全部是Protected的
+//所以不能直接通过new一个AlertDialog来创建出一个AlertDialog.
+
+//要创建一个AlertDialog，就要用到AlertDialog,Builder 中的create()方法
+//如这里的 dialog 就是新建了一个AlertDialog dialog.setTitle(R.string.app_name);
+//为对话框设置标题
+dialog.setMessage(mSnippet);
+//为对话框设置内容
+dialog.setPositiveButton(R.string.notealert_ok, this);
+//给对话框添加"Yes"按钮 if (isScreenOn()) {
+dialog.setNegativeButton(R.string.notealert_enter, this);}
+//对话框添加"No"按钮
+dialog.show().setOnDismissListener(this);
+
+public void onClick(DialogInterface dialog, int which) { switch (which) {
+//用which 来选择 click后下一步的操作 case DialogInterface.BUTTON_NEGATIVE:
+//这是取消操作
+Intent intent = new Intent(this, NoteEditActivity.class);//实现两个类间的数据传输
+
+/*
+*Get currentMinute
+*@return The Current Minute
+
+public int getCurrentMinute(){
+return mDate.get(Calendar.MINUTE);
+/**
+*Set current minute
+public void setCurrentMinute(int minute){
+if (!mlnitialising && minute ==getCurrentMinute()) { return;
+
+mMinuteSpinner.setValue(minute);
+
+mDate.set(Calendar.MINUTE,minute); onDateTimeChanged();
+
+1**
+*@return true lf this is in 24 hour view else false.
+\
+public boolean is24HourView (){ return mls24HourView;
+
+/*
+*Set whether in 24 hour or AM/PM mode.
+*@param is24HourView True for 24 hour mode. False for AM/PM mode.
+public void set24HourView(boolean is24HourView){
+// TODO Auto-generated catch block e.printStackTrace();
+//e.printStackTrace()函数功能是抛出异常，还将显示出更深的调用信息
+//System.out.printin(e)，这个方法打印出异常，并且输出在哪里出现的异常
+}catch (SecurityException e) {
+// TODO Auto-generated catch block 
+e.printStackTrace();
+} catch (IllegalStateException e)
+{
+// TODO Auto-generated catch block e.printStackTrace();} catch (I0Exception e)
+ {
+// TODO Auto-generated catch block e.printStackTrace();
+
+private void showActionDialog(){
+AlertDialog.Builder dialog = new AlertDialog.Builder(this);
+//AlertDialog的构造方法全部是Protected的
+//所以不能直接通过new一个AlertDialog来创建出一个AlertDialog。
+//要创建一个AlertDialog，就要用到AlertDialog.Builder中的create()方法
+
+//为对话框设置标题
+dialog.setMessage(mSnippet);
+//为对话框设置内容
+dialog.setPositiveButton(R.string.notealert_ok, this);
+//给对话框添加"Yes"按钮 if (isScreenOn()) {
+dialog.setNegativeButton(R.string.notealert_enter, this);}
+//对话框添加"No"按钮
+dialog.show().setOnDismissListener(this);
+
+public void onClick(Dialoginterface dialog, int which) { 
+switch (which) {
+//用which 来选择click后下一步的操作 case DialogInterface.BUTTON NEGATIVE:
+//这是取消操作
+Intent intent = new Intent(this, NoteEditActivity.class);
+//实现两个类间的数据传输
+
+
+if (mls24HourView== is24HourView) { return;
+mls24HourView= is24HourView;
+mAmPmSpinner.setVisibility(is24HourView?View.GONE:View.VISIBLE); 
+int hour = getCurrentHourOfDay(); 
+updateHourControl(); setCurrentHour(hour); 
+updateAmPmControl();
+
+private void updateDateControl(){
+Calendar cal =Calendar.getlnstance();
+cal.setTimelnMillis(mDate.getTimelnMillis());
+cal.add(Calendar.DAY OF YEAR,-DAYS IN ALL WEEK/2-1); 
+mDateSpinner.setDisplayedValues(null); for (inti=0;i<DAYS_IN_ALL_WEEK; ++i) { 
+cal.add(Calendar.DAY_OF_YEAR, 1);
+mDateDisplayValues[i] = (String) DateFormat.format("MM.dd EEEE", cal);
+mDateSpinner.setDisplayedValues(mDateDisplayValues); 
+mDateSpinner.setValue(DAYS_IN_ALL_WEEK/ 2); mDateSpinner.invalidate();}
+//对于星期几的算法
+private void updateAmPmControl(){ if (mls24HourView) {
+mAmPmSpinner.setVisibility(View.GONE);}else{
+int index= mlsAm ? Calendar.AM:Calendar.PM; 
+mAmPmSpinner.setValue(index);
+mAmPmSpinner.setVisibility(View.VISIBLE);}
+//对于上下午操作的算法
+
+private void updateHourControl(){ if (mls24HourView) {
+mHourSpinner.setMinValue(HOUR_SPINNER_MIN_VAL_24_HOUR_VIEW);
+mHourSpinner.setMaxValue(HOUR_SPINNER_MAX_VAL_24_HOUR_VIEW);}else{
+mHourSpinner.setMinValue(HOUR_SPINNER_MIN_VAL_12_HOUR_VIEW);
+mHourSpinner.setMaxValue(HOUR_SPINNER_MAX_VAL_12_HOUR_VIEW);}
+//对与小时的算法
+
+*Set the callback that indicates the 'Set' button has been pressed.* @param callback the callback, if null will do nothing
+public void setOnDateTimeChangedListener(OnDateTimeChangedListener callback){ 
+mOnDateTimeChangedListener =callback;
+package net.micode.notes.data;
+
+import android.content.ContentValues;
+import android.content.Context;
+import android.database.sqlite.SQLiteDatabase;
+import android.database.sqlite.SQLiteOpenHelper;
+import android.util.Log;
+
+import net.micode.notes.data.Notes.DataColumns;
+import net.micode.notes.data.Notes.DataConstants;
+import net.micode.notes.data.Notes.NoteColumns;
+
+/**
+ * 笔记数据库帮助类，用于创建和管理笔记数据库
+ */
+public class NotesDatabaseHelper extends SQLiteOpenHelper {
+    private static final String DB_NAME = "note.db"; // 数据库名称
+
+    private static final int DB_VERSION = 4; // 数据库版本号
+
+
+
+MediaPlayer mPlayer;
+
+@Override
+protected vold onCreate(Bundle savedInstanceState) { 
+	super.onCreate(savedInstanceState);
+//Bundle类型的数据与Map类型的数据相似，都是以key-value的形式存储数据的
+//onsavelnstanceState方法是用来保存Activity的状态的
+//能从 onCreate的参数savedInsanceState中获得状态数据 
+requestWindowFeature(Window.FEATURE_NO_TITLE);
+//界面显示一-无标题
+final Window win=getWindow();
+win.addFlags(WindowManager.LayoutParams.FLAG SHOW_WHEN LOCKED);
+if (lisScreenOn()){
+win.addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON
+//保持窗体点亮
+WindowManager.LayoutParams.FLAG_TURN_SCREEN_ON
+//将窗体点亮
+|WindowManager.LayoutParams.FLAG_ALLOW_LOCK_WHILE_SCREEN_ON
+//允许窗体点亮时锁屏
+WindowManager.LayoutParams.FLAG_LAYOUT_INSET_DECOR);]
+//在手机锁屏后如果到了闹钟提示时间，点亮屏幕
+Intent intent =getIntent();
+try{
+mNoteld=Long.valueOf(intent.getData().getPathSegments().get(1));
+mSnippet =DataUtils.getSnippetByld(this.getContentResolver(), mNoteld);
+//根据ID从数据库中获取标签的内容:
+//getContentResolver()是实现数据共享，实例存储。
+mSnippet = mSnippet.length() >SNIPPET_PREW_MAX_LEN ? mSnippet.substring(0,
+SNIPPET_PREW_MAX_LEN)+getResources().getString(R.string.notelist_string_info):mSnippet;
+//判断标签片段是否达到符合长度} catch (IllegalArgumentException e){ e.printStackTrace(); return;
+
+try
+// 代码区
+
+catch(Exception e)
+//异常处理
+代码区如果有错误，就会返回所写异常的处理。*/ mPlayer = new MediaPlayer();
+if (DataUtils,visibleInNoteDatabase(getContentResolver(), mNoteld, Notes.TYPE_NOTE)) { showActionDialog();
+试访	试读	
+//弹出对话框 playAlarmSound();//闹钟提示音激发}else{ finish();
+//完成闹钟动作
+
+private boolean isScreenOn(){
+//判断屏幕是否锁屏，调用系统函数判断
+PowerManager pm = (PowerManager) getSystemService(Context.POWER_SERVICE); return pm.isScreenOn();
+
+private vold playAlarmSound() {//闹钟提示音激发
+Uri	url	RingtoneManager.getActualDefaultRingtoneUri(this,	
+RingtoneManager.TYPE_ALARM);
+//调用系统的铃声管理URI，得到闹钟提示音
+int silentModeStreams =Settings.System.getInt(getContentResolver(),
+Settings.System.MODE_RINGER_STREAMS_AFFECTED,0);
+if ((silentModeStreams & (1<<AudioManager.STREAM_ALARM)) != 0) {
+mPlayer.setAudioStreamType(silentModeStreams);
+}else{
+mPlayer.setAudioStreamType(AudioManager.STREAM_ALARM);
+}
+try{
+mPlayer.setDataSource(this, url);
+//方法:setDataSource(Context context, Uri uri)
+//解释:无返回值，设置多媒体数据来源[根据Uni]
+mPlayer.prepare();
+//准备同步
+mPlayer.setLooping(true);
+//设置是否循环播放
+
+mPlayer.start();
+//开始播放
+} catch (IllegalArgumentException e) {
+// TODO Auto-generated catch block e.printStackTrace();
+//e.printStackTrace()函数功能是抛出异常，还将显示出更深的调用信息
+//System.out.printin(e)，这个方法打印出异常，并且输出在哪里出现的异常
+}catch (SecurityException e) {
+// TODO Auto-generated catch block 
+e.printStackTrace();
+} catch (IllegalStateException e)
+{
+// TODO Auto-generated catch block e.printStackTrace();} catch (I0Exception e)
+ {
+// TODO Auto-generated catch block e.printStackTrace();
+
+private void showActionDialog(){
+AlertDialog.Builder dialog = new AlertDialog.Builder(this);
+//AlertDialog的构造方法全部是Protected的
+//所以不能直接通过new一个AlertDialog来创建出一个AlertDialog。
+//要创建一个AlertDialog，就要用到AlertDialog.Builder中的create()方法
+
+//为对话框设置标题
+dialog.setMessage(mSnippet);
+//为对话框设置内容
+dialog.setPositiveButton(R.string.notealert_ok, this);
+//给对话框添加"Yes"按钮 if (isScreenOn()) {
+dialog.setNegativeButton(R.string.notealert_enter, this);}
+//对话框添加"No"按钮
+dialog.show().setOnDismissListener(this);
+
+public void onClick(Dialoginterface dialog, int which) { 
+switch (which) {
+//用which 来选择click后下一步的操作 case DialogInterface.BUTTON NEGATIVE:
+//这是取消操作
+Intent intent = new Intent(this, NoteEditActivity.class);
+//实现两个类间的数据传输
+
+
+if (mls24HourView== is24HourView) { return;
+mls24HourView= is24HourView;
+mAmPmSpinner.setVisibility(is24HourView?View.GONE:View.VISIBLE); 
+int hour = getCurrentHourOfDay(); 
+updateHourControl(); setCurrentHour(hour); 
+updateAmPmControl();
+
+private void updateDateControl(){
+Calendar cal =Calendar.getlnstance();
+cal.setTimelnMillis(mDate.getTimelnMillis());
+cal.add(Calendar.DAY OF YEAR,-DAYS IN ALL WEEK/2-1); 
+mDateSpinner.setDisplayedValues(null); for (inti=0;i<DAYS_IN_ALL_WEEK; ++i) { 
+cal.add(Calendar.DAY_OF_YEAR, 1);
+mDateDisplayValues[i] = (String) DateFormat.format("MM.dd EEEE", cal);
+mDateSpinner.setDisplayedValues(mDateDisplayValues); 
+mDateSpinner.setValue(DAYS_IN_ALL_WEEK/ 2); mDateSpinner.invalidate();}
+//对于星期几的算法
+private void updateAmPmControl(){ if (mls24HourView) {
+mAmPmSpinner.setVisibility(View.GONE);}else{
+int index= mlsAm ? Calendar.AM:Calendar.PM; 
+mAmPmSpinner.setValue(index);
+mAmPmSpinner.setVisibility(View.VISIBLE);}
+//对于上下午操作的算法
+
+private void updateHourControl(){ if (mls24HourView) {
+mHourSpinner.setMinValue(HOUR_SPINNER_MIN_VAL_24_HOUR_VIEW);
+mHourSpinner.setMaxValue(HOUR_SPINNER_MAX_VAL_24_HOUR_VIEW);}else{
+mHourSpinner.setMinValue(HOUR_SPINNER_MIN_VAL_12_HOUR_VIEW);
+mHourSpinner.setMaxValue(HOUR_SPINNER_MAX_VAL_12_HOUR_VIEW);}
+//对与小时的算法
+
+*Set the callback that indicates the 'Set' button has been pressed.* @param callback the callback, if null will do nothing
+public void setOnDateTimeChangedListener(OnDateTimeChangedListener callback){ 
+mOnDateTimeChangedListener =callback;
+package net.micode.notes.data;
+
+import android.content.ContentValues;
+import android.content.Context;
+import android.database.sqlite.SQLiteDatabase;
+import android.database.sqlite.SQLiteOpenHelper;
+import android.util.Log;
+
+import net.micode.notes.data.Notes.DataColumns;
+import net.micode.notes.data.Notes.DataConstants;
+import net.micode.notes.data.Notes.NoteColumns;
+
+/**
+ * 笔记数据库帮助类，用于创建和管理笔记数据库
+ */
+public class NotesDatabaseHelper extends SQLiteOpenHelper {
+    private static final String DB_NAME = "note.db"; // 数据库名称
+
+    private static final int DB_VERSION = 4; // 数据库版本号
+
+    /**
+     * 定义数据库表的接口
+     */
+    public interface TABLE {
+        public static final String NOTE = "note"; // 笔记表
+
+        public static final String DATA = "data"; // 数据表
+    }
+
+    private static final String TAG = "NotesDatabaseHelper"; // 日志标签
+
+    private static NotesDatabaseHelper mInstance; // 数据库帮助类实例
+
+    /**
+     * 创建笔记表的 SQL 语句
+     */
+    private static final String CREATE_NOTE_TABLE_SQL =
+        "CREATE TABLE " + TABLE.NOTE + "(" +
+            NoteColumns.ID + " INTEGER PRIMARY KEY," +
+            NoteColumns.PARENT_ID + " INTEGER NOT NULL DEFAULT 0," +
+            NoteColumns.ALERTED_DATE + " INTEGER NOT NULL DEFAULT 0," +
+            NoteColumns.BG_COLOR_ID + " INTEGER NOT NULL DEFAULT 0," +
+            NoteColumns.CREATED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +
+            NoteColumns.HAS_ATTACHMENT + " INTEGER NOT NULL DEFAULT 0," +
+            NoteColumns.MODIFIED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +
+            NoteColumns.NOTES_COUNT + " INTEGER NOT NULL DEFAULT 0," +
+            NoteColumns.SNIPPET + " TEXT NOT NULL DEFAULT ''," +
+            NoteColumns.TYPE + " INTEGER NOT NULL DEFAULT 0," +
+            NoteColumns.WIDGET_ID + " INTEGER NOT NULL DEFAULT 0," +
+            NoteColumns.WIDGET_TYPE + " INTEGER NOT NULL DEFAULT -1," +
+            NoteColumns.SYNC_ID + " INTEGER NOT NULL DEFAULT 0," +
+            NoteColumns.LOCAL_MODIFIED + " INTEGER NOT NULL DEFAULT 0," +
+            NoteColumns.ORIGIN_PARENT_ID + " INTEGER NOT NULL DEFAULT 0," +
+            NoteColumns.GTASK_ID + " TEXT NOT NULL DEFAULT ''," +
+            NoteColumns.VERSION + " INTEGER NOT NULL DEFAULT 0" +
+        ")";
+
+    /**
+     * 创建数据表的 SQL 语句
+     */
+    private static final String CREATE_DATA_TABLE_SQL =
+        "CREATE TABLE " + TABLE.DATA + "(" +
+            DataColumns.ID + " INTEGER PRIMARY KEY," +
+            DataColumns.MIME_TYPE + " TEXT NOT NULL," +
+            DataColumns.NOTE_ID + " INTEGER NOT NULL DEFAULT 0," +
+            NoteColumns.CREATED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +
+            NoteColumns.MODIFIED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +
+            DataColumns.CONTENT + " TEXT NOT NULL DEFAULT ''," +
+            DataColumns.DATA1 + " INTEGER," +
+            DataColumns.DATA2 + " INTEGER," +
+            DataColumns.DATA3 + " TEXT NOT NULL DEFAULT ''," +
+            DataColumns.DATA4 + " TEXT NOT NULL DEFAULT ''," +
+            DataColumns.DATA5 + " TEXT NOT NULL DEFAULT ''" +
+        ")";
+
+    // 这里可能还有其他方法，比如构造函数、数据库升级方法等
+}
+
+private static final String CREATE_DATA_NOTE_ID_INDEX_SQL =
+    "CREATE INDEX IF NOT EXISTS note_id_index ON " +
+    TABLE.DATA + "(" + DataColumns.NOTE_ID + ");";
+
+/**
+ * 当将笔记移动到文件夹时增加文件夹的笔记计数
+ */
+private static final String NOTE_INCREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER =
+    "CREATE TRIGGER increase_folder_count_on_update "+
+    " AFTER UPDATE OF " + NoteColumns.PARENT_ID + " ON " + TABLE.NOTE +
+    " BEGIN " +
+    "  UPDATE " + TABLE.NOTE +
+    "   SET " + NoteColumns.NOTES_COUNT + "=" + NoteColumns.NOTES_COUNT + " + 1" +
+    "  WHERE " + NoteColumns.ID + "=new." + NoteColumns.PARENT_ID + ";" +
+    " END";
+
+/**
+ * 当从文件夹中移除笔记时减少文件夹的笔记计数
+ */
+private static final String NOTE_DECREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER =
+    "CREATE TRIGGER decrease_folder_count_on_update " +
+    " AFTER UPDATE OF " + NoteColumns.PARENT_ID + " ON " + TABLE.NOTE +
+    " BEGIN " +
+    "  UPDATE " + TABLE.NOTE +
+    "   SET " + NoteColumns.NOTES_COUNT + "=" + NoteColumns.NOTES_COUNT + "-1" +
+    "  WHERE " + NoteColumns.ID + "=old." + NoteColumns.PARENT_ID +
+    "  AND " + NoteColumns.NOTES_COUNT + ">0" + ";" +
+    " END";
+
+/**
+ * 当将新的笔记插入文件夹时增加文件夹的笔记计数
+ */
+private static final String NOTE_INCREASE_FOLDER_COUNT_ON_INSERT_TRIGGER =
+    "CREATE TRIGGER increase_folder_count_on_insert " +
+    " AFTER INSERT ON " + TABLE.NOTE +
+    " BEGIN " +
+    "  UPDATE " + TABLE.NOTE +
+    "   SET " + NoteColumns.NOTES_COUNT + "=" + NoteColumns.NOTES_COUNT + " + 1" +
+    "  WHERE " + NoteColumns.ID + "=new." + NoteColumns.PARENT_ID + ";" +
+    " END";
+
+/**
+ * 当从文件夹中删除笔记时减少文件夹的笔记计数
+ */
+private static final String NOTE_DECREASE_FOLDER_COUNT_ON_DELETE_TRIGGER =
+    "CREATE TRIGGER decrease_folder_count_on_delete " +
+    " AFTER DELETE ON " + TABLE.NOTE +
+    " BEGIN " +
+    "  UPDATE " + TABLE.NOTE +
+    "   SET " + NoteColumns.NOTES_COUNT + "=" + NoteColumns.NOTES_COUNT + "-1" +
+    "  WHERE " + NoteColumns.ID + "=old." + NoteColumns.PARENT_ID +
+    "  AND " + NoteColumns.NOTES_COUNT + ">0;" +
+    " END";
+
+/**
+ * 当插入类型为 {@link DataConstants#NOTE} 的数据时更新笔记内容
+ */
+private static final String DATA_UPDATE_NOTE_CONTENT_ON_INSERT_TRIGGER =
+    "CREATE TRIGGER update_note_content_on_insert " +
+    " AFTER INSERT ON " + TABLE.DATA +
+    " WHEN new." + DataColumns.MIME_TYPE + "='" + DataConstants.NOTE + "'" +
+    " BEGIN" +
+    "  UPDATE " + TABLE.NOTE +
+    "   SET " + NoteColumns.SNIPPET + "=new." + DataColumns.CONTENT +
+    "  WHERE " + NoteColumns.ID + "=new." + DataColumns.NOTE_ID + ";" +
+    " END";
+
+/**
+ * 当类型为 {@link DataConstants#NOTE} 的数据发生更改时更新笔记内容
+ */
+private static final String DATA_UPDATE_NOTE_CONTENT_ON_UPDATE_TRIGGER =
+    "CREATE TRIGGER update_note_content_on_update " +
+    " AFTER UPDATE ON " + TABLE.DATA +
+    " WHEN old." + DataColumns.MIME_TYPE + "='" + DataConstants.NOTE + "'" +
+    " BEGIN" +
+    "  UPDATE " + TABLE.NOTE +
+    "   SET " + NoteColumns.SNIPPET + "=new." + DataColumns.CONTENT +
+    "  WHERE " + NoteColumns.ID + "=new." + DataColumns.NOTE_ID + ";" +
+    " END";
+```java
+/**
+ * 当类型为 {@link DataConstants#NOTE} 的数据被删除时，更新笔记内容
+ */
+private static final String DATA_UPDATE_NOTE_CONTENT_ON_DELETE_TRIGGER =
+    "CREATE TRIGGER update_note_content_on_delete " +
+    "AFTER delete ON " + TABLE.DATA +
+    " WHEN old." + DataColumns.MIME_TYPE + "='" + DataConstants.NOTE + "'" +
+    " BEGIN" +
+    "  UPDATE " + TABLE.NOTE +
+    "   SET " + NoteColumns.SNIPPET + "=''" +
+    "  WHERE " + NoteColumns.ID + "=old." + DataColumns.NOTE_ID + ";" +
+    " END";
+
+/**
+ * 删除已删除笔记所属的数据
+ */
+private static final String NOTE_DELETE_DATA_ON_DELETE_TRIGGER =
+    "CREATE TRIGGER delete_data_on_delete " +
+    "AFTER DELETE ON " + TABLE.NOTE +
+    " BEGIN" +
+    "  DELETE FROM " + TABLE.DATA +
+    "   WHERE " + DataColumns.NOTE_ID + "=old." + NoteColumns.ID + ";" +
+    " END";
+
+/**
+ * 删除已删除文件夹所属的笔记
+ */
+private static final String FOLDER_DELETE_NOTES_ON_DELETE_TRIGGER =
+    "CREATE TRIGGER folder_delete_notes_on_delete " +
+    "AFTER DELETE ON " + TABLE.NOTE +
+    " BEGIN" +
+    "  DELETE FROM " + TABLE.NOTE +
+    "   WHERE " + NoteColumns.PARENT_ID + "=old." + NoteColumns.ID + ";" +
+    " END";
+
+/**
+ * 将已移至回收站的文件夹中的笔记移动至回收站
+ */
+private static final String FOLDER_MOVE_NOTES_ON_TRASH_TRIGGER =
+    "CREATE TRIGGER folder_move_notes_on_trash " +
+    "AFTER UPDATE ON " + TABLE.NOTE +
+    " WHEN new." + NoteColumns.PARENT_ID + "=" + Notes.ID_TRASH_FOLER +
+    " BEGIN" +
+    "  UPDATE " + TABLE.NOTE +
+    "   SET " + NoteColumns.PARENT_ID + "=" + Notes.ID_TRASH_FOLER +
+    "  WHERE " + NoteColumns.PARENT_ID + "=old." + NoteColumns.ID + ";" +
+    " END";
+
+public NotesDatabaseHelper(Context context) {
+    super(context, DB_NAME, null, DB_VERSION);
+}
+
+public void createNoteTable(SQLiteDatabase db) {
+    db.execSQL(CREATE_NOTE_TABLE_SQL);
+    reCreateNoteTableTriggers(db);
+    createSystemFolder(db);
+    Log.d(TAG, "note table has been created");
+}
+
+private void reCreateNoteTableTriggers(SQLiteDatabase db) {
+    db.execSQL("DROP TRIGGER IF EXISTS increase_folder_count_on_update");
+    db.execSQL("DROP TRIGGER IF EXISTS decrease_folder_count_on_update");
+    db.execSQL("DROP TRIGGER IF EXISTS decrease_folder_count_on_delete");
+    db.execSQL("DROP TRIGGER IF EXISTS delete_data_on_delete");
+    db.execSQL("DROP TRIGGER IF EXISTS increase_folder_count_on_insert");
+    db.execSQL("DROP TRIGGER IF EXISTS folder_delete_notes_on_delete");
+    db.execSQL("DROP TRIGGER IF EXISTS folder_move_notes_on_trash");
+
+    db.execSQL(NOTE_INCREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER);
+    db.execSQL(NOTE_DECREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER);
+    db.execSQL(NOTE_DECREASE_FOLDER_COUNT_ON_DELETE_TRIGGER);
+    db.execSQL(NOTE_DELETE_DATA_ON_DELETE_TRIGGER);
+    db.execSQL(NOTE_INCREASE_FOLDER_COUNT_ON_INSERT_TRIGGER);
+    db.execSQL(FOLDER_DELETE_NOTES_ON_DELETE_TRIGGER);
+    db.execSQL(FOLDER_MOVE_NOTES_ON_TRASH_TRIGGER);
+}
+
+private void createSystemFolder(SQLiteDatabase db) {
+    ContentValues values = new ContentValues();
+
+    /**
+     * 为通话笔记创建通话记录文件夹
+     */
+    values.put(NoteColumns.ID, Notes.ID_CALL_RECORD_FOLDER);
+    values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
+    db.insert(TABLE.NOTE, null, values);
+
+    /**
+     * 根文件夹，即默认文件夹
+     */
+    values.clear();
+    values.put(NoteColumns.ID, Notes.ID_ROOT_FOLDER);
+    values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
+    db.insert(TABLE.NOTE, null, values);
+
+    /**
+     * 临时文件夹，用于移动笔记
+     */
+    values.clear();
+    values.put(NoteColumns.ID, Notes.ID_TEMPARAY_FOLDER);
+    values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
+    db.insert(TABLE.NOTE, null, values);
+
+    /**
+     * 创建回收站文件夹
+     */
+    values.clear();
+    values.put(NoteColumns.ID, Notes.ID_TRASH_FOLER);
+    values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
+    db.insert(TABLE.NOTE, null, values);
+}
+
+public void createDataTable(SQLiteDatabase db) {
+    db.execSQL(CREATE_DATA_TABLE_SQL);
+    reCreateDataTableTriggers(db);
+    db.execSQL(CREATE_DATA_NOTE_ID_INDEX_SQL);
+    Log.d(TAG, "data table has been created");
+}
+
+private void reCreateDataTableTriggers(SQLiteDatabase db) {
+    db.execSQL("DROP TRIGGER IF EXISTS update_note_content_on_insert");
+    db.execSQL("DROP TRIGGER IF EXISTS update_note_content_on_update");
+    db.execSQL("DROP TRIGGER IF EXISTS update_note_content_on_delete");
+
+    db.execSQL(DATA_UPDATE_NOTE_CONTENT_ON_INSERT_TRIGGER);
+    db.execSQL(DATA_UPDATE_NOTE_CONTENT_ON_UPDATE_TRIGGER);
+    db.execSQL(DATA_UPDATE_NOTE_CONTENT_ON_DELETE_TRIGGER);
+}
+
+
+```java
+/**
+ * 获取数据库辅助类的实例，使用了同步锁确保线程安全
+ * @param context 上下文对象
+ * @return NotesDatabaseHelper 实例
+ */
+static synchronized NotesDatabaseHelper getInstance(Context context) {
+    if (mInstance == null) {
+        mInstance = new NotesDatabaseHelper(context);
+    }
+    return mInstance;
+}
+
+@Override
+public void onCreate(SQLiteDatabase db) {
+    // 创建笔记表和数据表
+    createNoteTable(db);
+    createDataTable(db);
+}
+
+@Override
+public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
+    boolean reCreateTriggers = false; // 是否需要重新创建触发器
+    boolean skipV2 = false; // 是否跳过版本2的升级
+
+    if (oldVersion == 1) {
+        upgradeToV2(db); // 升级到版本2
+        skipV2 = true; // 此次升级包含了从版本2到版本3的升级
+        oldVersion++;
+    }
+
+    if (oldVersion == 2 && !skipV2) {
+        upgradeToV3(db); // 升级到版本3
+        reCreateTriggers = true;
+        oldVersion++;
+    }
+
+    if (oldVersion == 3) {
+        upgradeToV4(db); // 升级到版本4
+        oldVersion++;
+    }
+
+    // 如果需要重新创建触发器，则执行相应的方法
+    if (reCreateTriggers) {
+        reCreateNoteTableTriggers(db);
+        reCreateDataTableTriggers(db);
+    }
+
+    // 如果旧版本号与新版本号不匹配，则抛出异常
+    if (oldVersion != newVersion) {
+        throw new IllegalStateException("升级笔记数据库到版本 " + newVersion + " 失败");
+    }
+}
+
+/**
+ * 升级到版本2的方法
+ * @param db SQLiteDatabase 对象
+ */
+private void upgradeToV2(SQLiteDatabase db) {
+    db.execSQL("DROP TABLE IF EXISTS " + TABLE.NOTE); // 删除笔记表
+    db.execSQL("DROP TABLE IF EXISTS " + TABLE.DATA); // 删除数据表
+    createNoteTable(db); // 重新创建笔记表
+    createDataTable(db); // 重新创建数据表
+}
+
+/**
+ * 升级到版本3的方法
+ * @param db SQLiteDatabase 对象
+ */
+private void upgradeToV3(SQLiteDatabase db) {
+    // 删除不再使用的触发器
+    db.execSQL("DROP TRIGGER IF EXISTS update_note_modified_date_on_insert");
+    db.execSQL("DROP TRIGGER IF EXISTS update_note_modified_date_on_delete");
+    db.execSQL("DROP TRIGGER IF EXISTS update_note_modified_date_on_update");
+    // 添加一个用于保存 Gtask ID 的列
+    db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.GTASK_ID
+            + " TEXT NOT NULL DEFAULT ''");
+    // 添加一个垃圾箱系统文件夹
+    ContentValues values = new ContentValues();
+    values.put(NoteColumns.ID, Notes.ID_TRASH_FOLER);
+    values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
+    db.insert(TABLE.NOTE, null, values);
+}
+
+/**
+ * 升级到版本4的方法
+ * @param db SQLiteDatabase 对象
+ */
+private void upgradeToV4(SQLiteDatabase db) {
+    // 添加一个版本号的列
+    db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.VERSION
+            + " INTEGER NOT NULL DEFAULT 0");
+}
+
+