Summary of Android data persistence tools

Summary of Android data persistence tools

Programmers are the lazy creature and never duplicate the wheel during development. In actual development, data eating is a problem that must be solved, I will summarize several tool classes in addition to processing sqlite, because sqlite Can Use orm directly, and persistent data can be stored in I/O, SharedPreference, and other methods.

External Storage card

Package cn.edu. zafu. utils; import java. io. file; import java. io. fileInputStream; import java. io. fileNotFoundException; import java. io. fileOutputStream; import java. io. IOException; import java. io. unsupportedEncodingException; import android. OS. environment;/*** external memory card tool class * requires permission to be added * android. permission. WRITE_EXTERNAL_STORAGE * android. permission. MOUNT_UNMOUNT_FILESYSTEMS ** @ author lizhangqu * @ version 1.0 * */Public class ExternalStorageUtil {/*** whether to write ** @ return writability */public static boolean isExternalStorageWritable () {String state = Environment. getExternalStorageState (); if (Environment. MEDIA_MOUNTED.equals (state) {return true;} return false;}/*** readable ** @ return readability */public static boolean isExternalStorageReadable () {String state = Environment. getExternalStorageState (); if (Environment. MEDIA_MOU NTED. equals (state) | Environment. MEDIA_MOUNTED_READ_ONLY.equals (state) {return true;} return false;}/*** obtain the root path ** @ return external memory card root path */public static String getExternalStoragePath () {if (isExternalStorageWritable () return Environment. getExternalStorageDirectory (). getAbsolutePath (); elsereturn null;}/*** get the download directory path ** @ return external memory card download path */public static String getExternalDownloadPath () {return Environm Ent. getExternalStoragePublicDirectory (Environment. DIRECTORY_DOWNLOADS ). getAbsolutePath ();} /*** write the file to the root path ** @ param fileName file name * @ param content Context * @ return indicates whether the file is successfully written */public static boolean write (String fileName, String content) {return write ("/", fileName, content );} /*** write byte to the root directory ** @ param fileName file name * @ param bytes file byte array * @ return write successful */public static boolean writeBytes (String fileName, byt E [] bytes) {return writeBytes ("/", fileName, bytes);}/*** write a string to the file in the specified directory, the path starts with/and ends with ** @ param path: the path relative to the root path. The path starts, end with/* @ param fileName file name * @ param content File content * @ return write successful */public static boolean write (String path, String fileName, String content) {return writeBytes (path, fileName, content. getBytes ();}/*** write a byte array to the file in the specified directory. The path starts/ends with/** @ param path relative to the root path, path starts with/and ends with/* @ param fileNam E file name * @ param bytes byte array * @ return */public static boolean writeBytes (String path, String fileName, byte bytes []) {boolean flag = false; if (! Path. equals ("/") {File dir = new File (getExternalStoragePath () + path); if (! Dir. exists () {if (! (Dir. mkdir () | dir. isDirectory () {// File directory creation failed or not a directory return false; }}} file File = new File (getExternalStoragePath () + path + fileName ); fileOutputStream fos = null; try {fos = new FileOutputStream (file, false); fos. write (bytes); flag = true;} catch (FileNotFoundException e) {e. printStackTrace ();} catch (IOException e) {e. printStackTrace ();} finally {if (fos! = Null) {try {fos. close ();} catch (IOException e) {e. printStackTrace () ;}} return flag ;} /*** read byte from the root path ** @ param fileName file name * @ return byte array */public static byte [] readBytes (String fileName) {return readBytes ("/", fileName);}/*** read bytes from the specified directory. The path starts with/and ends with ** @ param path relative to the root path. The path starts, end with/* @ param fileName File name * @ return byte array */public static byte [] readBytes (String path, String fileName) {file File file = n Ew File (getExternalStoragePath () + path + fileName); if (! File. isFile () {return null;} else {FileInputStream FD = null; try {fiis = new FileInputStream (file); int length = fiis. available (); byte [] buffer = new byte [length]; FCM. read (buffer); return buffer;} catch (FileNotFoundException e) {e. printStackTrace ();} catch (IOException e) {e. printStackTrace ();} finally {if (FS! = Null) {try {FS. close ();} catch (IOException e) {e. printStackTrace () ;}} return null ;}} /*** read text from the root directory ** @ param fileName file name * @ return String */public static String read (String fileName) {return read ("/", fileName);}/*** read text from the specified directory. The path starts with/and ends with ** @ param path relative to the root path. The path starts, end with/* @ param fileName file name * @ return String */public static String read (String path, String fileName) {try {byte [] readBytes = readBytes (path, fileName ); if (readBytes = null) {return null;} return new String (readBytes, "UTF-8");} catch (UnsupportedEncodingException e) {e. printStackTrace ();} return null;}/*** delete from the root directory ** @ param fileName file name * @ return delete successful */public static boolean delete (String fileName) {return delete ("/", fileName);}/*** delete from the specified directory. The path starts/ends with/** @ param path relative to the root path, path starts with/and ends with/* @ param fileName file name * @ return: whether the deletion is successful */public static boolean delete (String path, String fileName) {File file = new File (getExternalStoragePath () + path + fileName); if (file. exists () return file. delete (); elsereturn true ;}}

Built-in storage card

Package cn.edu. zafu. utils; import java. io. file; import java. io. fileInputStream; import java. io. fileNotFoundException; import java. io. fileOutputStream; import java. io. IOException; import java. io. unsupportedEncodingException; import android. content. context; /*** internal memory card tool class ** @ author lizhangqu * @ version 1.0 */public class InternalStorageUtil {/*** Append content after the original file ** @ param context * @ param fileName file name * @ p The text appended by aram content * @ return whether the append is successful */public static boolean append (Context context, String fileName, String content) {return writeBytes (context, fileName, content. getBytes (), true);}/*** write to the file, if a file exists, it overwrites the ** @ param context Context * @ param fileName file name * @ param content written text * @ return whether the file is successfully written */public static boolean write (context, string fileName, String content) {return writeBytes (context, fileNam E, content. getBytes (), false );} /***** write byte ** @ param context Context * @ param fileName file name * @ param content write byte * @ return write successful */public static boolean writeBytes (context, string fileName, byte [] content) {return writeBytes (context, fileName, content, false);}/*** write to the file, when a file exists, determine whether to overwrite the ** @ param context * @ param fileName file name * @ param content written byte * @ param isAppend whether to append * @ retur N whether the write is successful */public static boolean writeBytes (Context context, String fileName, byte [] content, boolean isAppend) {FileOutputStream fout = null; boolean flag = false; try {if (isAppend) {fout = context. openFileOutput (fileName, Context. MODE_APPEND);} else {fout = context. openFileOutput (fileName, Context. MODE_PRIVATE);} fout. write (content); flag = true;} catch (FileNotFoundException e) {e. printStackTrace () ;} Catch (IOException e) {e. printStackTrace ();} finally {try {if (fout! = Null) {fout. close (); fout = null ;}} catch (IOException e) {e. printStackTrace () ;}} return flag ;} /*** read File ** @ param context Context * @ param fileName file name * @ return file content String */public static String read (context, String fileName) {byte [] buffer = readBytes (context, fileName); String result = null; try {result = new String (buffer, "UTF-8");} catch (UnsupportedEncodingException e) {e. printStackTrace ();} Return result;}/*** @ param context Context * @ param fileName file name * @ return byte array */public static byte [] readBytes (context, String fileName) {FileInputStream fin = null; byte [] buffer = null; try {fin = context. openFileInput (fileName); int length = fin. available (); buffer = new byte [length]; fin. read (buffer);} catch (FileNotFoundException e) {e. printStackTrace ();} catch (IOException e) {e. printStac KTrace ();} finally {try {if (fin! = Null) {fin. close (); fin = null ;}} catch (IOException e) {e. printStackTrace () ;}} return buffer;}/*** clear all files, if a file is not cleared, false is returned ** @ param context Context * @ return: whether the file is clear */public static boolean clear (context) {boolean flag = true; string [] files = context. fileList (); for (String fileName: files) {boolean result = context. deleteFile (fileName); if (result = false) {flag = false ;}} return flag ;} /*** clear the file by file name ** @ param context Context * @ param fileName file name * @ return whether the file is successfully deleted */public static boolean delete (context, String fileName) {return context. deleteFile (fileName);}/*** returns the absolute path of the internal storage ** @ param context Context * @ return app built-in folder path */public static String getFileDir (context) {File filesDir = context. getFilesDir (); return filesDir. getAbsolutePath ();}}

Read resource files

Package cn.edu. zafu. utils; import java. io. IOException; import java. io. inputStream; import java. io. unsupportedEncodingException; import android. content. context; /*** read assert resources ** @ author lizhangqu * @ version 1.0 */public class ResouceFileUtil {/*** read text resources from the assert folder ** @ param context * @ param fileName file name * @ return file content String */public static String readStringFromAssert (Context context, string file Name) {String result = null; byte [] buffer = readBytesFromAssert (context, fileName); try {result = new String (buffer, "UTF-8");} catch (UnsupportedEncodingException e) {e. printStackTrace ();} return result ;} /*** read text resources from the raw folder ** @ param context Context * @ param rawId raw resource id * @ return file content String */public static String readStringFromRaw (context, int rawId) {String result = null; byte [] buffer = readB YtesFromRaw (context, rawId); try {result = new String (buffer, "UTF-8");} catch (UnsupportedEncodingException e) {e. printStackTrace ();} return result ;} /*** read the file from the assert folder to the byte array ** @ param context Context * @ param fileName file name * @ return file byte array */public static byte [] readBytesFromAssert (context context, string fileName) {InputStream is = null; byte [] buffer = null; try {is = context. getAssets (). open (fileNam E); int size = is. available (); buffer = new byte [size]; is. read (buffer);} catch (IOException e) {e. printStackTrace ();} finally {if (is! = Null) {try {is. close (); is = null;} catch (IOException e) {e. printStackTrace () ;}} return buffer ;} /*** read the file from the raw folder to the byte array ** @ param context * @ param rawId raw resource id * @ return file byte array */public static byte [] readBytesFromRaw (Context context, int rawId) {InputStream is = null; byte [] buffer = null; try {is = context. getResources (). openRawResource (rawId); int size = is. available (); buffer = new byte [size ]; Is. read (buffer);} catch (IOException e) {e. printStackTrace ();} finally {if (is! = Null) {try {is. close (); is = null;} catch (IOException e) {e. printStackTrace () ;}} return buffer ;}}

SharedPreference operation

Package cn.edu. zafu. utils; import android. content. context; import android. content. sharedPreferences; /*** tool class for persistent data in SharedPreference mode ** @ author lizhangqu * @ version 1.0 */public class SharedPreferenceUtil {/*** Save the key-Value Pair ** @ param context * @ param fileName file name * @ param key * @ param value * @ return whether the file is saved successfully */public static boolean set (Context context, string fileName, String key, String value) {SharedPreferences sharedPreferences = context. getSharedPreferences (fileName, Context. MODE_PRIVATE); SharedPreferences. editor editor = sharedPreferences. edit (); editor. putString (key, value); return editor. commit ();}/*** get the key value, if not, return "" ** @ param context * @ param fileName file name * @ param key * @ return value, if not, "" */public static String get (Context context, String fileName, String key) {return get (context, fileName, key, "");} is returned ,"");} /*** get the value corresponding to the key, if not, return defaultValue ** @ param context * @ param fileName file name * @ param key * @ param defaultValue default * @ return value, if no value exists, ultvalue */public static String get (Context context, String fileName, String key, String defaultValue) {SharedPreferences sharedPreferences = context. getSharedPreferences (fileName, Context. MODE_PRIVATE); String value = sharedPreferences. getString (key, defaultValue); // The second parameter is the default value return value ;} /*** remove an item * @ param context Context * @ param fileName file name * @ param key * @ return whether the file is successfully removed */public static boolean remove (context, String fileName, string key) {SharedPreferences sharedPreferences = context. getSharedPreferences (fileName, Context. MODE_PRIVATE); SharedPreferences. editor editor = sharedPreferences. edit (); editor. remove (key); return editor. commit ();}/*** clear file content * @ param context Context * @ param fileName file name * @ return whether the file is cleared successfully */public static boolean clear (context, string fileName) {SharedPreferences sharedPreferences = context. getSharedPreferences (fileName, Context. MODE_PRIVATE); SharedPreferences. editor editor = sharedPreferences. edit (); editor. clear (); return editor. commit ();} /*** whether a certain item exists * @ param context * @ param fileName file name * @ param key * @ return whether the value corresponding to this key exists */public static boolean contatins (context context, string fileName, String key) {SharedPreferences sharedPreferences = context. getSharedPreferences (fileName, Context. MODE_PRIVATE); return sharedPreferences. contains (key );}}