Creating temporary files in Android

Question

What s the best way to create a temporary file in Android    Can File createTempFile be used  The documentation is very vague about it   In particular  it s not clear when temporary files created with File createTempFile are deleted  if ever

User · Answer

Do it in simple  According to documentation  https   developer android com training data-storage files  String imageName    IMG     String valueOf System currentTimeMillis       jpg           picFile   new File ProfileActivity this getCacheDir   imageName     and delete it after usage   picFile delete

User · Answer

You can use the cache dir using context getCacheDir     File temp File createTempFile  prefix   suffix  context getCacheDir

User · Answer

You can use the File deleteOnExit   method  https   developer android com reference java io File html deleteOnExit    It is referenced here https   developer android com reference java io File html createTempFile java lang String  java lang String  java io File

User · Answer

This is what I typically do   File outputDir   context getCacheDir       context being the Activity pointer File outputFile   File createTempFile  prefix    extension   outputDir     As for their deletion  I am not complete sure either  Since I use this in my implementation of a cache  I manually delete the oldest files till the cache directory size comes down to my preset value

User · Answer

For temporary internal files their are 2 options  1   File file   file   File createTempFile filename  null  this getCacheDir       2   File file file   new File this getCacheDir    filename     Both options adds files in the applications cache directory and thus can be cleared to make space as required but option 1 will add a random number on the end of the filename to keep files unique  It will also add a file extension which is  tmp by default  but it can be set to anything via the use of the 2nd parameter  The use of the random number means despite specifying a filename it doesn t stay the same as the number is added along with the suffix file extension   tmp by default  e g you specify your filename as internal file and comes out as internal file1456345 tmp  Whereas you can specify the extension you can t specify the number that is added  You can however find the filename it generates via file getName     but you would need to store it somewhere so you can use it whenever you wanted for example to delete or read the file  Therefore for this reason I prefer the 2nd option as the filename you specify is the filename that is created

User · Answer

Best practices on internal and external temporary files   Internal Cache     If you d like to cache some data  rather than store it persistently    you should use getCacheDir   to open a File that represents the   internal directory where your application should save temporary cache   files       When the device is low on internal storage space  Android may delete   these cache files to recover space  However  you should not rely on   the system to clean up these files for you  You should always maintain   the cache files yourself and stay within a reasonable limit of space   consumed  such as 1MB  When the user uninstalls your application    these files are removed    External Cache     To open a File that represents the external storage directory where   you should save cache files  call getExternalCacheDir    If the user   uninstalls your application  these files will be automatically   deleted       Similar to ContextCompat getExternalFilesDirs    mentioned above    you can also access a cache directory on a secondary external storage    if available  by calling ContextCompat getExternalCacheDirs              Tip  To preserve file space and maintain your app s performance  it s     important that you carefully manage your cache files and remove those     that aren t needed anymore throughout your app s lifecycle

[android] Creating temporary files in Android

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