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tool/BackupUtils.java 代码注释

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master
feng 3 years ago
parent 11d55da229
commit 86b3b1879f
1 changed files with 28 additions and 23 deletions
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51
src/Notes/app/src/main/java/net/micode/notes/tool/BackupUtils.java
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@ -39,10 +39,14 @@ import java.io.PrintStream;
public class BackupUtils {
private static final String TAG = "BackupUtils";
// Singleton stuff
private static BackupUtils sInstance;
private static BackupUtils sInstance; //类里面为什么可以定义自身类的对象
public static synchronized BackupUtils getInstance(Context context) {
//ynchronized 关键字，代表这个方法加锁,相当于不管哪一个线程（例如线程A）
//运行到这个方法时,都要检查有没有其它线程B（或者C、 D等）正在用这个方法(或者该类的其他同步方法)，有的话要等正在使用synchronized方法的线程B（或者C 、D）运行完这个方法后再运行此线程A,没有的话,锁定调用者,然后直接运行
//它包括两种用法：synchronized 方法和 synchronized 块
if (sInstance == null) {
//如果当前备份不存在，则新声明一个
sInstance = new BackupUtils(context);
}
return sInstance;
@ -52,24 +56,24 @@ public class BackupUtils {
* Following states are signs to represents backup or restore
* status
*/
// Currently, the sdcard is not mounted
// Currently, the sdcard is not mounted SD卡没有被装入手机
public static final int STATE_SD_CARD_UNMOUONTED = 0;
// The backup file not exist
// The backup file not exist 备份文件夹不存在
public static final int STATE_BACKUP_FILE_NOT_EXIST = 1;
// The data is not well formated, may be changed by other programs
// The data is not well formated, may be changed by other programs 数据已被破坏，可能被修改
public static final int STATE_DATA_DESTROIED = 2;
// Some run-time exception which causes restore or backup fails
// Some run-time exception which causes restore or backup fails 超时异常
public static final int STATE_SYSTEM_ERROR = 3;
// Backup or restore success
// Backup or restore success 成功存储
public static final int STATE_SUCCESS = 4;
private TextExport mTextExport;
private BackupUtils(Context context) {
mTextExport = new TextExport(context);
}
} //初始化函数
private static boolean externalStorageAvailable() {
private static boolean externalStorageAvailable() { //外部存储功能是否可用
return Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState());
}
@ -128,19 +132,19 @@ public class BackupUtils {
public TextExport(Context context) {
TEXT_FORMAT = context.getResources().getStringArray(R.array.format_for_exported_note);
mContext = context;
mFileName = "";
mFileName = ""; //为什么为空?
mFileDirectory = "";
}
private String getFormat(int id) {
return TEXT_FORMAT[id];
}
} //获取文本的组成部分
/**
* Export the folder identified by folder id to text
*/
private void exportFolderToText(String folderId, PrintStream ps) {
// Query notes belong to this folder
// Query notes belong to this folder 通过查询parent id是文件夹id的note来选出制定ID文件夹下的Note
Cursor notesCursor = mContext.getContentResolver().query(Notes.CONTENT_NOTE_URI,
NOTE_PROJECTION, NoteColumns.PARENT_ID + "=?", new String[] {
folderId
@ -149,13 +153,13 @@ public class BackupUtils {
if (notesCursor != null) {
if (notesCursor.moveToFirst()) {
do {
// Print note's last modified date
// Print note's last modified date ps里面保存有这份note的日期
ps.println(String.format(getFormat(FORMAT_NOTE_DATE), DateFormat.format(
mContext.getString(R.string.format_datetime_mdhm),
notesCursor.getLong(NOTE_COLUMN_MODIFIED_DATE))));
// Query data belong to this note
String noteId = notesCursor.getString(NOTE_COLUMN_ID);
exportNoteToText(noteId, ps);
exportNoteToText(noteId, ps); //将文件导出到text
} while (notesCursor.moveToNext());
}
notesCursor.close();
@ -172,7 +176,7 @@ public class BackupUtils {
}, null);
if (dataCursor != null) {
if (dataCursor.moveToFirst()) {
if (dataCursor.moveToFirst()) { //利用光标来扫描内容，区别为callnote和note两种，靠ps.printline输出
do {
String mimeType = dataCursor.getString(DATA_COLUMN_MIME_TYPE);
if (DataConstants.CALL_NOTE.equals(mimeType)) {
@ -181,7 +185,7 @@ public class BackupUtils {
long callDate = dataCursor.getLong(DATA_COLUMN_CALL_DATE);
String location = dataCursor.getString(DATA_COLUMN_CONTENT);
if (!TextUtils.isEmpty(phoneNumber)) {
if (!TextUtils.isEmpty(phoneNumber)) { //判断是否为空字符
ps.println(String.format(getFormat(FORMAT_NOTE_CONTENT),
phoneNumber));
}
@ -218,7 +222,8 @@ public class BackupUtils {
/**
* Note will be exported as text which is user readable
*/
public int exportToText() {
public int exportToText() { //总函数，调用上面的exportFolder和exportNote
if (!externalStorageAvailable()) {
Log.d(TAG, "Media was not mounted");
return STATE_SD_CARD_UNMOUONTED;
@ -229,7 +234,7 @@ public class BackupUtils {
Log.e(TAG, "get print stream error");
return STATE_SYSTEM_ERROR;
}
// First export folder and its notes
// First export folder and its notes 将根目录里的便签导出（由于不属于任何文件夹，因此无法通过文件夹导出来实现这一部分便签的导出）
Cursor folderCursor = mContext.getContentResolver().query(
Notes.CONTENT_NOTE_URI,
NOTE_PROJECTION,
@ -297,7 +302,7 @@ public class BackupUtils {
PrintStream ps = null;
try {
FileOutputStream fos = new FileOutputStream(file);
ps = new PrintStream(fos);
ps = new PrintStream(fos); //将ps输出流输出到特定的文件，目的就是导出到文件，而不是直接输出
} catch (FileNotFoundException e) {
e.printStackTrace();
return null;
@ -314,16 +319,16 @@ public class BackupUtils {
*/
private static File generateFileMountedOnSDcard(Context context, int filePathResId, int fileNameFormatResId) {
StringBuilder sb = new StringBuilder();
sb.append(Environment.getExternalStorageDirectory());
sb.append(context.getString(filePathResId));
File filedir = new File(sb.toString());
sb.append(Environment.getExternalStorageDirectory()); //外部（SD卡）的存储路径
sb.append(context.getString(filePathResId)); //文件的存储路径
File filedir = new File(sb.toString()); //filedir应该就是用来存储路径信息
sb.append(context.getString(
fileNameFormatResId,
DateFormat.format(context.getString(R.string.format_date_ymd),
System.currentTimeMillis())));
File file = new File(sb.toString());
try {
try { //如果这些文件不存在，则新建
if (!filedir.exists()) {
filedir.mkdir();
}
@ -336,7 +341,7 @@ public class BackupUtils {
} catch (IOException e) {
e.printStackTrace();
}
// try catch 异常处理
return null;
}
}

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