Android File IO Tutorial with Internal and External Storage

No permissions are required to read or write files to internal storage for your ... For apps the target Android 10 (API level 29) or higher, a new feature ... Skiptocontent InthistutorialIwillcoverhowtocreatefilesinvariousmethodsinAndroidsuchasInternalStorage,ExternalStorage,theMediaStoreAPIandtheStorageAccessFramework. Iwillexplainthedifferencesbetweeneachofthesefilestoragemethodsandprovidesomecontextonwhentouseeach. IwillalsocoversomedetailsontheScopedStorageprivacyfeaturereleasedinAndroid10andenhancedinAndroid11forfilescreatedbyyourappinexternalstorage. IwillsharecodesamplesinthistutorialandIhavealsopublishedallthecodefromthistutorialintheGitHubrepositoryinthelinkbelow. https://github.com/learntodroid/FileIOTutorial AndroidInternalFileStorageTutorial ThissectionofthepostcontainsatutorialonhowtouseinternalstorageinAndroid.WewillcoverthefollowingtopicsinourtutorialontheuseofinternalstorageinAndroid. WhatisInternalStorageinAndroid?HowtoCreateaTextFileProgrammaticallyinInternalStorageinAndroidHowtoWriteTexttoaFileProgrammaticallyinInternalStorageinAndroidHowtoReadTextfromaFileProgrammaticallyinInternalStorageinAndroidHowtoDeleteaTextFileProgrammaticallyfromInternalStorageinAndroidHowtoViewFilesinInternalStorageusingtheAndroidDeviceFileExplorerHowtoRemoveFilesfromInternalStorageusingtheAndroidStorageUtility PleaseseeascreencapturebelowoftheAndroidappofwhatwewillbecreatinginthistutorial. WhatisInternalStorageinAndroid? InternalStorageinAndroidisusedforstoringfilesthatareonlyvisibletoyourapp.Nopermissionsarerequiredtoreadorwritefilestointernalstorageforyourapp.Ifyourappisuninstalledwithfilesininternalstorage,thesefileswillbedeletedasapartoftheuninstallationprocess. FilesininternalstorageinAndroidcaneitherbepersistentfilesorcachefiles. Cachefilesarestoredininternalstorageastemporaryfiles,theywillgetdeletedwhentheuseruninstallstheappbuttheycanalsobedeletedbeforethenbytheAndroidsystemclearingspaceinstorageorbydeletingthecachefileprogrammatically.Unlikecachefiles,persistentfilesininternalstoragecannotbedeletedbytheAndroidsystemautomatically. HowtoCreateaTextFileProgrammaticallyinInternalStorageinAndroid TocreateatextfileprogrammaticallyininternalstorageinAndroidwewillbeusingtheFileclassfromthejava.io.Filepackage. InthecodesampleIhavecreated,IamallowingtheusertoenterthenameofthefileinsideanEditTextaswellasallowingthemtouseaToggleButtontochooseiftheywantapersistentfileoracachefiletobecreatedininternalstorage. WewillusetheFileconstructorandprovidetwoparameters,thefirstisofthedatatypeFilewhichreferstothedirectorywheretheFilewecreatewillresideandthesecondparameterisofthedatatypeStringwhichwillbethenameofthefile. Forpersistentfilesininternalstorageweneedtousethe“files”directoryinsidetheinternalstoragedirectory.ToobtainthisdirectoryusethegetFilesDir()methodontheapplicationcontextwhichwillreturnaFileobjectpointingthe“files”directory. Forcachefilesininternalstorageweneedtousethe“cache”directoryinsidetheinternalstoragedirectory.ToobtainthisdirectoryusethegetCacheDir()methodontheapplicationcontextwhichwillreturnaFileobjectpointingthe“cache”directory. Beforewecreatethefile,Iwillfirstcheckwhetheritalreadyexistsusingtheexists()methodontheFileobjectwhichwillreturntrueiftheFilealreadyexistsorfalseifitdoesnotexist. Ifthefiledoesn’texist,IwillproceedtocreatethefileusingthecreateNewFile()methodontheFileobject. PleaseseethecodeexcerptbelowforprogrammaticallycreatingeitherapersistentorcachefileininternalstorageinAndroid. HowtoWriteTexttoaFileProgrammaticallyinInternalStorageinAndroid TowritetexttoafileresidingintheinternalstorageofourappprogrammaticallywewillbeusingtheFileOutputStreamclassfromthejava.io.FileOutputStreampackage. Inourcodesample,wewillbewritingthefilenamethathasbeenenteredintheEditTextbytheuserandwilldetermineifthefileisapersistentfileoracachefilebasedonthecheckedstatusoftheToggleButton. Alsoinourcodesample,theuserwillenterthetexttheywishtowriteintothefileinanEditTextandselectthe“WriteFile”buttonwhentheyarereadytowritethetexttothefile. TosetuptheFileOutputStreamforwritingthetexttothefile,wewillfirstcheckifthefileisapersistentfileorcachefileininternalstorage. IfitisapersistentfilethenwewillsetuptheFileOutputStreamusingtheopenFileOutput(String,int)methodontheapplicationcontextpassingthefilenameandtheContext.MODE_PRIVATEflagasparameters.TheContext.MODE_PRIVATEflagforthefilecreationmodemeansthecreatedfilecanonlybeaccessedbythecallingapplication. IfthefileisacachefilethenwewillsetuptheFileOutputStreambypassingaFileobjectpointingtothecachefileasaparametertotheFileOutputStreamconstructor. ThentowritethetexttothefileusingtheFileOutputStreamwewillcallthewrite(byte[])methodbypassingabytearrayasaparameterthatconsistsofthetextfromthefilecontentsEditTextencodedusingtheUTF-8formatintoabytearray. PleaseseethecodeexcerptbelowforprogrammaticallywritingtexttoeitherapersistentorcachefileininternalstorageinAndroid. HowtoReadTextfromaFileProgrammaticallyinInternalStorageinAndroid ToreadthetextfromafileresidingintheinternalstorageofourappprogrammaticallywewillbeusingtheFileInputStreamclassfromthejava.io.FileInputStreampackage. Inourcodesample,wewilloverwritethefilecontentsEditTextwiththetextreadfromthefileenteredintofilenameEditTextwhentheuserselectsthe“ReadFile”button. TosetuptheFileInputStreamforreadingthetextfromthefile,wewillfirstcheckifthefileisapersistentfileoracachefileininternalstorage. IfitisapersistentfilethenwewillsetuptheFileInputStreamusingtheopenFileInput(String)methodontheapplicationcontextpassingthefilenameasaparameter. IfthefileisacachefilethenwewillsetuptheFileInputStreambypassingaFileobjectpointingtothecachefileasaparametertotheFileInputStreamconstructor. ThenwecreatewillanInputStreamReaderfromtheFileInputStreamandusethattocreateaBufferedReaderwhichallowsustoreadfromthefileonelineatatime.WewillcreateanemptyArrayListofStringstostoreeachlineoftextfromthefile. NextwewillusetheBufferedReaderinsideawhilelooptoextracteachlineoftextoneatatimeuntilthereisnomoretext.EachlineoftextreadusingtheBufferedReaderwillbeinsertedintotheArrayListsequentially. Onceallofthelinesoftexthavebeenreadfromthefilewewillusethejoin(…)methodfromtheTextUtilsclasstocreateasingleStringoftextbyjoiningallofthelinesoftextintheArrayListtogetherwithanewlinecharacterbetweenalllinesoftext.ThiswillallowthetexttobeformattedcorrectlywhendisplayedintheEditTextcontainingthefilecontents. PleaseseethecodeexcerptbelowforprogrammaticallyreadingtextfromaeitherapersistentorcachefileininternalstorageinAndroid. HowtoDeleteaTextFileProgrammaticallyfromInternalStorageinAndroid TodeleteafileresidingintheinternalstorageofourappprogrammaticallywewillbeusingtheFileclassfromthejava.io.Filepackage. FirstwewillcreateFileobjectpointingtheFilewewanttodeletebyusingthefilenameenteredbytheuserandselectingtheappropriatefiledirectorybasedonwhetherthefileisapersistentfileoracachefile. Thenwewillusetheexists()methodontheFileobjecttoconfirmthatitexists,andifitdoesexistwewillproceedtodeleteusingthedelete()methodontheFileobject. PleaseseethecodeexcerptbelowforprogrammaticallydeletingeitherapersistentorcachefileininternalstorageinAndroid. HowtoViewFilesinInternalStorageusingtheAndroidDeviceFileExplorer TheDeviceFileExplorerisatoolavailableinAndroidStudiothatallowsyoutoviewallofthefilesontheAndroiddeviceconnectedtoAndroidStudio. TheDeviceFileExplorercanbeusedtoreadboththepersistentandcachefilesinsideinternalstorageofyourAndroidapp. ToaccesstheDeviceFileExplorerinAndroidStudioselectthe“View”menu,hoverover“ToolWindows”andselectthe“DeviceFileExplorer”menuitem. TheDeviceFileExplorerwillloadontherightsideofAndroidStudioandwilldisplayafiletreeofallofthedirectoriesandfilesontheAndroiddevice. Tolocatepersistentfilesininternalstorageofyourappnavigatethroughtothefollowingdirectory. data/data//files Tolocatecachefilesininternalstorageofyourappnavigatethroughtothefollowingdirectory. data/data//cache YoucanalsoopenanyfiletoreadinsideAndroidStudiobydoubleclickingonthefilename. HowtoRemoveFilesfromInternalStorageusingtheAndroidStorageUtility ItispossibletouseastorageutilityanAndroiddevicetoremovepersistentandcachefilesfromtheinternalstorageofyourapp. InthestorageutilityshownintheGIFbelow.ThetotalamountofstorageusedbyyourAndroidappbrokendownbytheAppsize,UserdataandCacheisshownalongwithabuttonto“Clearstorage”andabuttonto“Clearcache”. Selectingthe“Clearstorage”buttonwilldeleteallpersistentandcachefilesfromtheinternalstorageofyourapp. Selectingthe“Clearcache”buttonwilldeleteonlythecachefilesfromtheinternalstorageofyourappleavingthepersistentfilesininternalstorage. AndroidExternalFileStorageTutorial WhatisExternalStorageinAndroid? InAndroidExternalStorageisusedforstoringfilesthatotherappsareabletoaccess.Externalstorageisbetterforstoringlargerfilesthatneedtobesharedwithotherapps. Filesinexternalstoragecanbeappspecific,meaningthatwhentheappisuninstalledthesefilesinexternalstoragewillbedeleted.Appspecificfilesinexternalstoragecanbepersistentfilesorcachefiles. ForAndroid4.4(APIlevel19)andhigher,nostoragerelatedpermissionsarerequiredtoaccessappspecificdirectorieswithexternalstorage. ForappsthetargetAndroid10(APIlevel29)orhigher,anewfeaturecalledscopedstorageisappliedbydefaulttoexternalstoragewhichwillpreventotherappsfromaccessingyourappspecificfilesinexternalstorage. ScopestoragecanbedisabledbyusingtherequestLegacyExternalStorageflagandsettingitto“true”intheAndroidapp’smanifest. TolearnmoreaboutscopedstoragecheckouttheYouTubevideobelow. https://www.youtube.com/watch?v=UnJ3amzJM94 Mediafilessuchasimages,audioandvideocanbeexposedtootherappsinexternalstoragethroughtheuseoftheAndroidMediaStoreAPI. OtherfilesyouwanttosharetootherappsinexternalstoragesuchasdocumentscanbesharedusingtheStorageAccessFramework. HowtoStorePersistentandCacheFilesinExternalStorageinAndroid AppspecificpersistentfilesinexternalstorageresideinadirectoryaccessibleusingthegetExternalFileDirs()method. AppspecificcachefilesinexternalstorageresideinadirectoryaccessibleusingthegetExternalCacheDirs()method. ThecodesamplebelowcontainscodeforwritingapersistentfileoracachefileintoexternalstorageinAndroid. ThecodesamplebelowcontainscodeforreadingapersistentfileoracachefilefromexternalstorageinAndroid. BelowisascreenshotofanAndroidappcreatingapersistentfileinappspecificexternalstorage. BelowisascreenshotoftheDeviceFileExplorerinAndroidStudioshowingthepersistentfilecreatedinappspecificexternalstorage. BelowisascreenshotofanAndroidappcreatingacachefileinappspecificexternalstorage. BelowisascreenshotoftheDeviceFileExplorerinAndroidStudioshowingthecachefilecreatedinappspecificexternalstorage. HowtoStoreMediaFilesinExternalStorageinAndroid Mediafilessuchasimages,videosandaudiocanbesharedinexternalstoragewithotherappsusingtheAndroidMediaStoreAPIprovidingtheyhavetheREAD_EXTERNAL_STORAGEpermission.MediafilessharedusingtheMediaStoreAPIwillnotbedeletedwhentheappisuninstalled. OnAndroid10(APIlevel29)orhigher,READ_EXTERNAL_STORAGEorWRITE_EXTERNAL_STORAGEpermissionsarerequiredtoaccessmediafilescreatedbyotherappsviatheMediaStoreAPI.OnAndroid9(APIlevel28)orlowerpermissionsarerequiredforaccessingallmediafilesviatheMediaStoreAPI. TodemonstratehowtostoragemediafilesinexternalstorageinAndroidusingtheMediaStoreAPI,IcreatedasampleappthatloadsanimagefromtheinternetusingtheGlidelibrarythenstoresitintothePicturesdirectoryinexternalstorageusingtheMediaStoreAPIforimages. TheappalsowilldisplayaRecyclerViewinagridlayoutofallimagesinthePicturesdirectoryretrievedusingtheMediaStoreAPI. IfyouwouldliketolearnmoreabouthowtosetupanduseGlideforimageloadinginyourAndroidappincludinghowtodownloadtheGlideusingGradleandhowtosetupthemanifesttoincludeinternetpermissions,checkoutthetutorialIwroteonhowtouseGlideatthelinkbelow. AndroidGlideTutorialwithExamplesinJava ForthissectionofthetutorialfirstwewillbecreatingaclassmodellinganimageretrievedfromtheMediaStoreAPI.SeethecodesamplefortheImageclassbelow. NextwewillbecreatingaRecyclerViewHolderclassfortheImagetodisplaytheImageintheRecyclerView.SeethecodesamplefortheImageViewHolderclassbelowwhichsetsthenameoftheImageintheTextViewandloadstheImageViewwithGlideinsidethebind(Image)method. ForthenextstepwewillcreateaRecyclerViewAdapterfortheRecyclerView.SeethecodesamplefortheGalleryRecyclerAdapterclassbelow. InthefinalstepinthissectionofthetutorialwewillcreateanActivityclassthatincludescodeforinsertinganImageintotheMediaStoreAPIandqueryingImagesfromtheMediaStoreAPIintotheRecyclerViewAdaptertobeshownintheRecyclerView. HowtoStoreDocumentsinExternalStorageinAndroid DocumentsandotherfilescanbesharedwithotherappsinexternalstorageusingtheStorageAccessFramework. NopermissionsarerequiredreadorwritefilesinexternalstoragetotheStorageAccessFramework.FilescreatedusingyourappviatheStorageAccessFrameworkwillnotautomaticallybedeletedwhenyouuninstallyourapp. PleaseseethecodesamplefortheactivityclassbelowthatcanreadandwritefilestoexternalstorageusingtheStorageAccessFramework. SeethescreencapturebelowshowingtheuserexperienceofcreatingandwritingtoatextdocumentgeneratingusingtheStorageAccessFramework. Sharethispost: ShareonFacebook ShareonTwitter ShareonEmail ShareonWhatsApp RecentPosts linktoHowtoCreateaPieChartinanAndroidAppwithMPAndroidChart https://www.youtube.com/watch?v=S3zqxVoIUig AllofthecodesamplesinthispostareavailableonGitHub. CodeSamples ProjectLevelBuild.GradleFile AppLevelBuild.Gradle...ContinueReading linktoHowtoCreateaBMICalculatorAndroidApp Asapartoftheseriesforcreatingappsfromscratch,IhaveputtogetheratutorialonhowtobuildaBMIcalculatorappforAndroid. 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