Android internal storage permissionAndroid Internal storageAndroid app folderAndroid/data/datarequestLegacyExternalStorageAndroid 11 write file to external storageAndroid 11 data folder emptyAndroid internal storageAndroid - Internal Storage - Tutorialspoint
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Android provides many kinds of storage for applications to store their data. These storage places are shared preferences, internal and external storage, ...
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Android-InternalStorage
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Androidprovidesmanykindsofstorageforapplicationstostoretheirdata.Thesestorageplacesaresharedpreferences,internalandexternalstorage,SQLitestorage,andstoragevianetworkconnection.
Inthischapterwearegoingtolookattheinternalstorage.Internalstorageisthestorageoftheprivatedataonthedevicememory.
Bydefaultthesefilesareprivateandareaccessedbyonlyyourapplicationandgetdeleted,whenuserdeleteyourapplication.
Writingfile
Inordertouseinternalstoragetowritesomedatainthefile,calltheopenFileOutput()methodwiththenameofthefileandthemode.Themodecouldbeprivate,publice.t.c.Itssyntaxisgivenbelow−
FileOutputStreamfOut=openFileOutput("filenamehere",MODE_WORLD_READABLE);
ThemethodopenFileOutput()returnsaninstanceofFileOutputStream.SoyoureceiveitintheobjectofFileInputStream.Afterthatyoucancallwritemethodtowritedataonthefile.Itssyntaxisgivenbelow−
Stringstr="data";
fOut.write(str.getBytes());
fOut.close();
Readingfile
Inordertoreadfromthefileyoujustcreated,calltheopenFileInput()methodwiththenameofthefile.ItreturnsaninstanceofFileInputStream.Itssyntaxisgivenbelow−
FileInputStreamfin=openFileInput(file);
Afterthat,youcancallreadmethodtoreadonecharacteratatimefromthefileandthenyoucanprintit.Itssyntaxisgivenbelow−
intc;
Stringtemp="";
while((c=fin.read())!=-1){
temp=temp+Character.toString((char)c);
}
//stringtempcontainsallthedataofthefile.
fin.close();
Apartfromthethemethodsofwriteandclose,thereareothermethodsprovidedbytheFileOutputStreamclassforbetterwritingfiles.Thesemethodsarelistedbelow−
Sr.No
Method&description
1
FileOutputStream(Filefile,booleanappend)
ThismethodconstructsanewFileOutputStreamthatwritestofile.
2
getChannel()
Thismethodreturnsawrite-onlyFileChannelthatsharesitspositionwiththisstream
3
getFD()
Thismethodreturnstheunderlyingfiledescriptor
4
write(byte[]buffer,intbyteOffset,intbyteCount)
ThismethodWritescountbytesfromthebytearraybufferstartingatpositionoffsettothisstream
Apartfromthethemethodsofreadandclose,thereareothermethodsprovidedbytheFileInputStreamclassforbetterreadingfiles.Thesemethodsarelistedbelow−
Sr.No
Method&description
1
available()
Thismethodreturnsanestimatednumberofbytesthatcanbereadorskippedwithoutblockingformoreinput
2
getChannel()
Thismethodreturnsaread-onlyFileChannelthatsharesitspositionwiththisstream
3
getFD()
Thismethodreturnstheunderlyingfiledescriptor
4
read(byte[]buffer,intbyteOffset,intbyteCount)
Thismethodreadsatmostlengthbytesfromthisstreamandstorestheminthebytearraybstartingatoffset
Example
Hereisanexampledemonstratingtheuseofinternalstoragetostoreandreadfiles.Itcreatesabasicstorageapplicationthatallowsyoutoreadandwritefrominternalstorage.
Toexperimentwiththisexample,youcanrunthisonanactualdeviceorinanemulator.
Steps
Description
1
YouwilluseAndroidStudioIDEtocreateanAndroidapplicationunderapackagecom.example.sairamkrishna.myapplication.
2
Modifysrc/MainActivity.javafiletoaddnecessarycode.
3
Modifytheres/layout/activity_maintoaddrespectiveXMLcomponents
4
Runtheapplicationandchoosearunningandroiddeviceandinstalltheapplicationonitandverifytheresults
Followingisthecontentofthemodifiedmainactivityfilesrc/MainActivity.java.
packagecom.example.sairamkrishna.myapplication;
importandroid.app.Activity;
importandroid.os.Bundle;
importandroid.view.View;
importandroid.widget.Button;
importandroid.widget.EditText;
importandroid.widget.TextView;
importandroid.widget.Toast;
importjava.io.FileInputStream;
importjava.io.FileOutputStream;
publicclassMainActivityextendsActivity{
Buttonb1,b2;
TextViewtv;
EditTexted1;
Stringdata;
privateStringfile="mydata";
@Override
protectedvoidonCreate(BundlesavedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
b1=(Button)findViewById(R.id.button);
b2=(Button)findViewById(R.id.button2);
ed1=(EditText)findViewById(R.id.editText);
tv=(TextView)findViewById(R.id.textView2);
b1.setOnClickListener(newView.OnClickListener(){
@Override
publicvoidonClick(Viewv){
data=ed1.getText().toString();
try{
FileOutputStreamfOut=openFileOutput(file,MODE_WORLD_READABLE);
fOut.write(data.getBytes());
fOut.close();
Toast.makeText(getBaseContext(),"filesaved",Toast.LENGTH_SHORT).show();
}
catch(Exceptione){
//TODOAuto-generatedcatchblock
e.printStackTrace();
}
}
});
b2.setOnClickListener(newView.OnClickListener(){
@Override
publicvoidonClick(Viewv){
try{
FileInputStreamfin=openFileInput(file);
intc;
Stringtemp="";
while((c=fin.read())!=-1){
temp=temp+Character.toString((char)c);
}
tv.setText(temp);
Toast.makeText(getBaseContext(),"fileread",Toast.LENGTH_SHORT).show();
}
catch(Exceptione){
}
}
});
}
}
Followingisthemodifiedcontentofthexmlres/layout/activity_main.xml.
Inthefollowingcodeabcindicatesthelogooftutorialspoint.com
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