Android Writing Logs to text File

Question

I m Trying to Write Logs to Custom Log txt File on Android File using this code of Mine but then this method creates file but contains nothing  Basically I want to read previous contents of the file and then append my data with the existing content    The Code is as follows    public static void write String str                 InputStream fileInputStream   null          FileOutputStream fileOutpurStream   null          try                        fileInputStream   new FileInputStream file               fileOutpurStream   new FileOutputStream file               if file exists                                  int ch   0                  int current   0                  StringBuffer buffer   new StringBuffer                    while  ch   fileInputStream read       -1                                        buffer append  char  ch                       current                                      byte data   new byte  int file length                     fileInputStream read data                      fileOutpurStream write data                   fileOutpurStream write str getBytes   0 str getBytes   length                   fileOutpurStream flush                               else                                  file createNewFile                    fileOutpurStream write str getBytes   0 str getBytes   length                   fileOutpurStream flush                                    catch Exception e                        e printStackTrace                      finally                       try                               fileInputStream close                    fileOutpurStream flush                    fileOutpurStream close                    fileOutpurStream   null                  fileInputStream   null                            catch  IOException e                                   TODO Auto-generated catch block                 e printStackTrace

User · Answer

Use slf4android lib   It s simple implementation of slf4j api using android java util logging     Features    logging to file out of the box logging to any other destination by LoggerConfiguration configuration   addHandlerToLogger shake your device to send logs with screenshot via email  really small  it tooks only  55kB   slf4android is maintained mainly by  miensol   Read more about slf4android on our blog    Introducing slf4android Integrate slf4android with Crashlytics

User · Answer

Many of the previous versions on log4j dont work now  05 2019   But you can use Hyperlog - I can confirm it works    Add this line to your dependencies  amp  sync project  implementation  com hypertrack hyperlog 0 0 10   Create a new application class  create a new java class and extend Application   Then in the onCreate method add these lines   HyperLog initialize this   HyperLog setLogLevel Log VERBOSE    HyperLog getDeviceLogsInFile this    Change manifest file to have application file defined    lt application     android name   AppClass             Different ways to log   HyperLog d TAG  debug    HyperLog i TAG  information    HyperLog e TAG  error    HyperLog v TAG  verbose    HyperLog w TAG  warning    HyperLog a TAG  assert    HyperLog exception TAG  exception  throwable    Find your log files  Navigate to  RootFolder android data  appPackageName LogFiles

User · Answer

In general  you must have a file handle before opening the stream   You have a fileOutputStream handle before createNewFile   in the else block   The stream does not create the file if it doesn t exist   Not really android specific  but that s a lot IO for this purpose   What if you do many  write  operations one after another   You will be reading the entire contents and writing the entire contents  taking time  and more importantly  battery life   I suggest using java io RandomAccessFile  seek   ing to the end  then writeChars   to append   It will be much cleaner code and likely much faster

User · Answer

I solved this problem with following piece of code in command line way   File outputFile   new File  pathToFile     Runtime getRuntime   exec  logcat -c    Runtime getRuntime   exec  logcat -v time -f     outputFile getAbsolutePath      Where  time  option adds metadata field details for date  invocation time  priority tag  and PID of the process issuing the message   Then in your code just do something similar to this  using android util Log    Log d  yourappname    Your message

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This variant is much shorter    try       final File path   new File              Environment getExternalStorageDirectory     DBO logs5        if   path exists              path mkdir              Runtime getRuntime   exec               logcat  -d -f     path   File separator                        dbo logcat                          txt      catch  IOException e        e printStackTrace

User · Answer

For those new to Java logging in general and Android logging   Log4j is generic java logging implementation and is now a project of Apache software foundation  It is not Android specific and so has some incompatibilities with Android  SL4J is not a logging implementation  It is  an abstraction layer  It helps avoid a situations like  each 3rd party library  dependencies to a project  trying to using its own logging implementation like Log4j  Source    Some options for logging to txt in Android are below   Use logcat -f as in this answer to log to file  Note that from Android 4 2  READ LOGS permission doesn t have any impact and every Application  unless phone is rooted  could only read its own logs  The  disadvantage here is logcat buffer is circular and has a size limit  You might not get earlier logs  Use microlog4android   written for mobile devices like Android   as in earlier answer  There could be a way  but I couldn t figure  how to use microlog4Android for logging to application internal storage  Only option for logs path was external storage like sdcard and so I couldn t use it  Use Log4j with android-logging-log4j  What does android-logging-log4j do   It makes Log4j easier to use in Android by giving two functions    option to send logs to logcat in addition to logging file a simple way to set Log4j configuration options like file path  max file size  number of backups etc by providing LogConfigurator class      Simple example below  Notice that logger object in below example is a Log4j object returned and not an android-logging-log4j class  So android-logging-log4j is used only for configuring Log4j  Yet to try LogBack  LogBack is developed by same person who came up with Log4J 1 x and SL4J libraries  Not related to Log4j 2 x though    Steps for using Log4j in Android    Add both log4j-1 2 x jar and android-logging-log4j-1 0 3 jar to the libs folder  Add permissions only if using external storage  lt uses-permission android name  android permission WRITE EXTERNAL STORAGE   gt  Write Log4j helper class  package com example logger   import android os Environment  import de mindpipe android logging log4j LogConfigurator   public class Log4jHelper       private final static LogConfigurator mLogConfigrator   new LogConfigurator         static           configureLog4j               private static void configureLog4j             String fileName   Environment getExternalStorageDirectory            log4j log           String filePattern     d -   c  -  p    m n           int maxBackupSize   10          long maxFileSize   1024   1024           configure  fileName  filePattern  maxBackupSize  maxFileSize               private static void configure  String fileName  String filePattern  int maxBackupSize  long maxFileSize             mLogConfigrator setFileName  fileName            mLogConfigrator setMaxFileSize  maxFileSize            mLogConfigrator setFilePattern filePattern           mLogConfigrator setMaxBackupSize maxBackupSize           mLogConfigrator setUseLogCatAppender true           mLogConfigrator configure                public static org apache log4j Logger getLogger  String name             org apache log4j Logger logger   org apache log4j Logger getLogger  name            return logger           In Activity class  org apache log4j Logger log  Log4jHelper getLogger   YourActivity     log error  Error    log info  Info    log warn  Warn       Example Source  Note that  log4j 2 x   improved functionalities   rewritten from scratch is not backward comptible with log4j 1 x  So you have to use log4j 1 2 x jar with android-logging-log4j jar  I was able to log to application internal file and later email the file with setReadable true  false

User · Answer

microlog4android works for me but the documentation is pretty poor  All they need to add is a this is a quick start tutorial   Here is a quick tutorial I found    Add the following static variable in your main Activity   private static final Logger logger   LoggerFactory getLogger     Add the following to your onCreate   method   PropertyConfigurator getConfigurator this  configure     Create a file named microlog properties and store it in assets directory Edit the microlog properties file as follows   microlog level DEBUG microlog appender LogCatAppender FileAppender microlog formatter PatternFormatter microlog formatter PatternFormatter pattern  c   P   m  T  Add logging statements like this   logger debug  M4A       For each class you create a logger object as specified in 1   6 You may be add the following permission        lt uses-permission android name  android permission WRITE EXTERNAL STORAGE    gt    Here is the source for tutorial

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Hope this can help     public void appendLog String text              File logFile   new File  sdcard log file       if   logFile exists               try                  logFile createNewFile                   catch  IOException e                      TODO Auto-generated catch block          e printStackTrace                    try              BufferedWriter for performance  true to set append to file flag       BufferedWriter buf   new BufferedWriter new FileWriter logFile  true           buf append text         buf newLine          buf close            catch  IOException e                TODO Auto-generated catch block       e printStackTrace

User · Answer

This may be late but hope this may help   Try this      public void writefile                 File externalStorageDir   Environment getExternalStorageDirectory            File myFile   new File externalStorageDir    yourfilename txt             if myFile exists                         try                       FileOutputStream fostream   new FileOutputStream myFile           OutputStreamWriter oswriter   new OutputStreamWriter fostream            BufferedWriter bwriter   new BufferedWriter oswriter              bwriter write  Hi welcome             bwriter newLine                        bwriter close             oswriter close             fostream close                      catch  IOException e                        e printStackTrace                            else                       try                   myFile createNewFile                              catch  IOException e                                 e printStackTrace                              here bfwritter newline writes your text into the file  And add the permission    lt uses-permission android name    android permission WRITE EXTERNAL STORAGE   gt    in your manifest file without fail

User · Answer

I have created a simple  lightweight class  about 260 LoC  that extends the standard android util Log implementation with file based logging  Every log message is logged via android util Log and also written to a text file on the device   You can find it on github  https   github com volkerv FileLog

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File logFile   new File filename       try        Process process   Runtime getRuntime   exec  quot logcat AndroidRuntime E   S      -f  quot    logFile              catch   Exception e          Basic Logger  quot Error Basic quot    quot error  quot  e      try this code for Writing Error Log in File

User · Answer

After long time of investigation I found that    android util Log by default use java util logging Logger LogCat uses logger with name     to get instance of it use LogManager getLogManager   getLogger     Android Devices adds to LogCat logger instance of com android internal logging AndroidHandler after run of debug apps But    com android internal logging AndroidHandler prints messages to logcat only with levels more then java util logging Level INFO such as  Level INFO  Level WARNING  Level SEVERE  Level OFF      So to write logs to file just simple to the rootLogger     add a java util logging FileHandler     class App   Application      override fun onCreate           super onCreate         Log d TAG  printLoggers  before setup           val rootLogger   java util logging LogManager getLogManager   getLogger           val dirFile   destinationFolder       val file   File dirFile  logFile txt         val handler   java util logging FileHandler file absolutePath  5  1024   1024  5Mb    1  true        handler formatter   AndroidLogFormatter filePath   file absolutePath         rootLogger  addHandler handler         Log d TAG  printLoggers  after setup               val destinationFolder  File         get                 val parent                    Environment getExternalStoragePublicDirectory Environment DIRECTORY DOWNLOADS  absoluteFile             val destinationFolder   File parent   MyApp               if   destinationFolder exists                      destinationFolder mkdirs                   destinationFolder mkdir                             return destinationFolder             class AndroidLogFormatter val filePath  String       var tagPrefix  String         Formatter          override fun format record  LogRecord   String           val tag   record getTag tagPrefix          val date   record getDate           val level   record getLogCatLevel           val message   record getLogCatMessage           return   date  level tag   message n           fun LogRecord getTag tagPrefix  String   String       val name   loggerName     val maxLength   30     val tag   tagPrefix    if  name length  gt  maxLength  name substring name length - maxLength  else name      return tag    fun LogRecord getDate    String        return Date millis  formatedBy  yyyy-MM-dd HH mm ss SSS      fun Date  formatedBy dateFormat  String   String        val date   this     date    return null     val writeFormat   SimpleDateFormat dateFormat  Locale getDefault      MM   HH mm     return writeFormat format date     fun LogRecord getLogCatMessage    String       var message   message      if  thrown    null            message    Log getStackTraceString thrown            return message    fun Int getAndroidLevel    Int       return when           this  gt   Level SEVERE intValue   - gt       SEVERE             Log ERROR                   this  gt   Level WARNING intValue   - gt       WARNING             Log WARN                   this  gt   Level INFO intValue   - gt       INFO             Log INFO                   else - gt                Log DEBUG                    fun LogRecord getLogCatLevel    String       return when  level intValue   getAndroidLevel              Log ERROR - gt       SEVERE              E                     Log WARN - gt       WARNING              W                     Log INFO - gt       INFO              I                     Log DEBUG - gt                 D                     else - gt                 D                      fun getLoggerLevel level  Int   Level       return when  level            Log ERROR - gt       SEVERE             Level SEVERE                   Log WARN - gt       WARNING             Level WARNING                   Log INFO - gt       INFO             Level INFO                   Log DEBUG - gt                Level FINE                   else - gt                Level FINEST                     To print all loggers at your app use   Log e TAG  printLoggers  before setup      private fun printLoggers caller  String  printIfEmpty  Boolean   true   String           val builder   StringBuilder           val loggerNames   LogManager getLogManager   loggerNames         builder appendln  --------------------------------------------------------------           builder appendln  printLoggers   caller           while  loggerNames hasMoreElements                  val element   loggerNames nextElement               val logger   LogManager getLogManager   getLogger element              val parentLogger  Logger    logger parent             val handlers   logger handlers             val level   logger  level             if   printIfEmpty  amp  amp  handlers isEmpty                      continue                           val handlersNames   handlers map                   val handlerName   it javaClass simpleName                 val formatter  Formatter    it formatter                 val formatterName   if  formatter is AndroidLogFormatter                           formatter javaClass simpleName    formatter filePath                      else                       formatter  javaClass  simpleName                                     handlerName  formatterName                             builder appendln  level   level logger     element   handlers   handlersNames parentLogger    parentLogger  name                      builder appendln  --------------------------------------------------------------           return builder toString

User · Answer

You should take a look at microlog4android  They have a solution ready to log to a file   http   code google com p microlog4android

User · Answer

You can use the library I ve written  It s very easy to use   Add this dependency to your gradle file   dependencies       compile  com github danylovolokh android-logger 1 0 2      Initialize the library in the Application class   File logsDirectory   AndroidLogger getDefaultLogFilesDirectory this       int logFileMaxSizeBytes   2   1024   1024     2Mb     try           AndroidLogger initialize                  this                  logsDirectory                   Log File Name                   logFileMaxSizeBytes                  false                          catch  IOException e               Some error happened - most likely there is no free space on the system         This is how you use the library   AndroidLogger v  TAG    Verbose Message      And this is how to retrieve the logs   AndroidLogger processPendingLogsStopAndGetLogFiles new AndroidLogger GetFilesCallback              Override         public void onFiles File   logFiles                   get everything you need from these files             try                   AndroidLogger reinitAndroidLogger                  catch  IOException e                    e printStackTrace                                      Here is the link to the github page with more information  https   github com danylovolokh AndroidLogger  Hope it helps

User · Answer

Warning  I may be totally misunderstanding you  but if all you want is a log file  why sweat   Put this in a bat file  change the path to your tools directory  and  yourappname is of course your app s name    cd  C  devAndroid Software android-sdk-windows-1 6 r1 android-sdk-windows-1 6 r1 tools  adb logcat -v time   ActivityManager W  yourappname D    W  gt  C  devAndroid log yourappname log    Then in your code just do something similar to this   Log d  yourappname    Your message      To create the log  connect the USB cable and run your bat file   Regards

[android] Android Writing Logs to text File

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