/* * Copyright (c) 2010-2011, The MiCode Open Source Community (www.micode.net) * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package net.micode.notes.tool; import android.content.Context; import android.database.Cursor; import android.os.Environment; import android.text.TextUtils; import android.text.format.DateFormat; import android.util.Log; import net.micode.notes.R; import net.micode.notes.data.Notes; import net.micode.notes.data.Notes.DataColumns; import net.micode.notes.data.Notes.DataConstants; import net.micode.notes.data.Notes.NoteColumns; import java.io.File; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.io.PrintStream; 好的,我将为`BackupUtils.java`文件中的每个语句提供更细致的注释: ```java public class BackupUtils { private static final String TAG = "BackupUtils"; // 定义日志标签,用于识别日志输出的来源 private static BackupUtils sInstance; // 声明一个静态实例变量,用于实现单例模式 // 提供一个公共的静态方法,用于获取BackupUtils的单例实例 public static synchronized BackupUtils getInstance(Context context) { if (sInstance == null) { sInstance = new BackupUtils(context); // 如果实例不存在,则新建一个实例 } return sInstance; // 返回单例实例 } // 定义一系列状态码,用于表示备份或恢复的状态 public static final int STATE_SD_CARD_UNMOUONTED = 0; // SD卡未挂载 public static final int STATE_BACKUP_FILE_NOT_EXIST = 1; // 备份文件不存在 public static final int STATE_DATA_DESTROIED = 2; // 数据格式不正确,可能被其他程序更改 public static final int STATE_SYSTEM_ERROR = 3; // 系统错误,导致备份或恢复失败 public static final int STATE_SUCCESS = 4; // 备份或恢复成功 private TextExport mTextExport; // TextExport对象,用于将数据导出到文本 // BackupUtils的私有构造函数,传入Context对象 private BackupUtils(Context context) { mTextExport = new TextExport(context); // 初始化TextExport对象 } // 检查外部存储(SD卡)是否可用 private static boolean externalStorageAvailable() { return Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState()); // 比较存储状态是否为已挂载 } // 导出数据到文本文件,并返回操作结果状态码 public int exportToText() { return mTextExport.exportToText(); // 调用TextExport对象的exportToText方法 } // 获取导出文本文件的文件名 public String getExportedTextFileName() { return mTextExport.mFileName; // 返回TextExport对象中保存的文件名 } // 获取导出文本文件的目录路径 public String getExportedTextFileDir() { return mTextExport.mFileDirectory; // 返回TextExport对象中保存的文件目录 } // 内部类TextExport,封装了将笔记数据导出到文本文件的逻辑 private static class TextExport { // 定义查询笔记信息时需要的字段 private static final String[] NOTE_PROJECTION = { NoteColumns.ID, NoteColumns.MODIFIED_DATE, NoteColumns.SNIPPET, NoteColumns.TYPE }; // 定义NOTE_PROJECTION数组中各个字段的索引 private static final int NOTE_COLUMN_ID = 0; private static final int NOTE_COLUMN_MODIFIED_DATE = 1; private static final int NOTE_COLUMN_SNIPPET = 2; // 定义查询笔记数据时需要的字段 private static final String[] DATA_PROJECTION = { DataColumns.CONTENT, DataColumns.MIME_TYPE, DataColumns.DATA1, DataColumns.DATA2, DataColumns.DATA3, DataColumns.DATA4, }; // 定义DATA_PROJECTION数组中各个字段的索引 private static final int DATA_COLUMN_CONTENT = 0; private static final int DATA_COLUMN_MIME_TYPE = 1; private static final int DATA_COLUMN_CALL_DATE = 2; private static final int DATA_COLUMN_PHONE_NUMBER = 4; // 用于格式化导出文本的字符串数组 private final String[] TEXT_FORMAT; // 定义格式化字符串数组中的索引 private static final int FORMAT_FOLDER_NAME = 0; private static final int FORMAT_NOTE_DATE = 1; private static final int FORMAT_NOTE_CONTENT = 2; private Context mContext; // 应用程序上下文 private String mFileName; // 导出文本文件的文件名 private String mFileDirectory; // 导出文本文件的目录 // TextExport类的构造函数,初始化上下文和格式化字符串数组 public TextExport(Context context) { TEXT_FORMAT = context.getResources().getStringArray(R.array.format_for_exported_note); // 从资源文件中获取格式化字符串数组 mContext = context; // 保存上下文对象 mFileName = ""; // 初始化文件名为空字符串 mFileDirectory = ""; // 初始化文件目录为空字符串 } // 根据索引获取格式化字符串 private String getFormat(int id) { return TEXT_FORMAT[id]; // 返回格式化字符串数组中指定索引的字符串 } // 导出指定文件夹ID的笔记到文本 private void exportFolderToText(String folderId, PrintStream ps) { // 查询属于该文件夹的笔记 Cursor notesCursor = mContext.getContentResolver().query(Notes.CONTENT_NOTE_URI, NOTE_PROJECTION, NoteColumns.PARENT_ID + "=?", new String[] { folderId }, null); if (notesCursor != null) { if (notesCursor.moveToFirst()) { do { // 打印笔记的最后修改日期 ps.println(String.format(getFormat(FORMAT_NOTE_DATE), DateFormat.format( mContext.getString(R.string.format_datetime_mdhm), notesCursor.getLong(NOTE_COLUMN_MODIFIED_DATE)))); // 查询属于该笔记的数据 String noteId = notesCursor.getString(NOTE_COLUMN_ID); exportNoteToText(noteId, ps); } while (notesCursor.moveToNext()); } notesCursor.close(); // 关闭游标 } } // 导出指定ID的笔记到文本 private void exportNoteToText(String noteId, PrintStream ps) { // 查询笔记数据 Cursor dataCursor = mContext.getContentResolver().query(Notes.CONTENT_DATA_URI, DATA_PROJECTION, DataColumns.NOTE_ID + "=?", new String[] { noteId }, null); if (dataCursor != null) { if (dataCursor.moveToFirst()) { do { String mimeType = dataCursor.getString(DATA_COLUMN_MIME_TYPE); if (DataConstants.CALL_NOTE.equals(mimeType)) { // 如果MIME类型为通话笔记,则打印电话号码、通话日期和位置 String phoneNumber = dataCursor.getString(DATA_COLUMN_PHONE_NUMBER); long callDate = dataCursor.getLong(DATA_COLUMN_CALL_DATE); String location = dataCursor.getString(DATA_COLUMN_CONTENT); if (!TextUtils.isEmpty(phoneNumber)) { ps.println(String.format(getFormat(FORMAT_NOTE_CONTENT), phoneNumber)); } ps.println(String.format(getFormat(FORMAT_NOTE_CONTENT), DateFormat .format(mContext.getString(R.string.format_datetime_mdhm), callDate))); if (!TextUtils.isEmpty(location)) { ps.println(String.format(getFormat(FORMAT_NOTE_CONTENT), location)); } } else if (DataConstants.NOTE.equals(mimeType)) { // 如果MIME类型为普通笔记,则打印笔记内容 String content = dataCursor.getString(DATA_COLUMN_CONTENT); if (!TextUtils.isEmpty(content)) { ps.println(String.format(getFormat(FORMAT_NOTE_CONTENT), content)); } } } while (dataCursor.moveToNext()); } dataCursor.close(); // 关闭游标 } // 打印笔记之间的分隔符 try { ps.write(new byte[] { Character.LINE_SEPARATOR, Character.LETTER_NUMBER }); } catch (IOException e) { Log.e(TAG, e.toString()); } } // 执行导出操作,将笔记数据导出为用户可读的文本格式 public int exportToText() { if (!externalStorageAvailable()) { Log.d(TAG, "Media was not mounted"); // 如果SD卡未挂载,则记录日志并返回状态码 return STATE_SD_CARD_UNMOUONTED; } PrintStream ps = getExportToTextPrintStream(); // 获取指向导出文本文件的PrintStream对象 if (ps == null) { Log.e(TAG, "get print stream error"); // 如果获取PrintStream失败,则记录日志并返回状态码 return STATE_SYSTEM_ERROR; } // 查询所有文件夹和其笔记,除了垃圾箱文件夹和通话记录文件夹 Cursor folderCursor = mContext.getContentResolver().query( Notes.CONTENT_NOTE_URI, NOTE_PROJECTION, "(" + NoteColumns.TYPE + "=" + Notes.TYPE_FOLDER + " AND " + NoteColumns.PARENT_ID + "<>" + Notes.ID_TRASH_FOLER + ") OR " + NoteColumns.ID + "=" + Notes.ID_CALL_RECORD_FOLDER, null, null); if (folderCursor != null) { if (folderCursor.moveToFirst()) { do { // 打印文件夹名称 String folderName = ""; if(folderCursor.getLong(NOTE_COLUMN_ID) == Notes.ID_CALL_RECORD_FOLDER) { folderName = mContext.getString(R.string.call_record_folder_name); // 如果是通话记录文件夹,则使用资源文件中的名称 } else { folderName = folderCursor.getString(NOTE_COLUMN_SNIPPET); // 否则,使用查询到的文件夹名称 } if (!TextUtils.isEmpty(folderName)) { ps.println(String.format(getFormat(FORMAT_FOLDER_NAME), folderName)); } String folderId = folderCursor.getString(NOTE_COLUMN_ID); exportFolderToText(folderId