问题
I'm developing an application in which I'm storing username and password in SharedPreferences. All things are working fine for me, storing as well as retrieving the values. But I discovered that when I restart the device or the app is force closed the value stored in SharedPreferences is reset. And when I again launch my app I get null values in SharedPreferences key. Here, is what I'm doing for storing the values:
SharedPreferences emailLoginSP;
emailLoginSP = PreferenceManager.getDefaultSharedPreferences(getApplicationContext());
emailLoginSP.edit().putString("prefEmailId", email_text).commit();
emailLoginSP.edit().putString("prefUserId", userIDToken).commit();
emailLoginSP.edit().putString("prefAccess_token", accessToken).commit();
Intent i = new Intent(LoginWithEmail.this,UserInfoActivity.class);
i.putExtra("acess_token", accessToken);
i.putExtra("user_id", userIDToken);
i.putExtra("emailID", email_text);
startActivity(i);
And, this is how I'm retriving it:
SharedPreferences emailLoginSP = PreferenceManager.getDefaultSharedPreferences(getApplicationContext());
loginEmail = emailLoginSP.getString("prefEmailId", null);
loginUserId = emailLoginSP.getString("prefUserId", null);
loginAccessToken = emailLoginSP.getString("prefAccess_token", null);
All things are working fine till now. Again I'm stating my problem that I get null values when I force close or restart my device. Can we store it permanently in the app memory? Or, I'm doing something wrong here?
Any help will be appreciated.
回答1:
I have a login screen and wanted the app to appear as if it's remained "logged in" at the internal screen after the app is closed/destroyed/phone call/etc.
I have a Preferences Object to save values following Login or Register. I read preference values in all the key screen onResume() methods.
After login (for example):
SharedPreferences app_preferences = PreferenceManager.getDefaultSharedPreferences(activity);
SharedPreferences.Editor editor = app_preferences.edit();
editor.putString("sessionId", application.currentSessionId);
editor.putString("userId", application.currentUserId);
editor.putString("userEmail", application.currentUserEmail);
editor.putString("siteUserId", application.currentSiteUserId);
editor.commit();
Within onResume() of Activities: (ie, within internal screens)
SharedPreferences app_preferences = PreferenceManager.getDefaultSharedPreferences(activity);
application.currentSessionId = app_preferences.getString("sessionId", "");
application.currentUserId = app_preferences.getString("userId", "");
application.currentUserEmail = app_preferences.getString("userEmail", "");
application.currentSiteUserId = app_preferences.getString("siteUserId", "");
Note. I have application "global" variables, ie, application.currentSessionId, you can just substitute your variables
Try something similar maybe your not saving or retrieving the values correctly because SharePreferences should work
回答2:
Hi ! Solution that worked for me!
Solution 1 Solution 2
Solution 1:
SharedPreferences sharedPreferences = getSharedPreferences("namefile", Context.MODE_PRIVATE);//store or retrieved file "namefile.xml". /*or SharedPreferences sharedPreferences =getActivity().getSharedPreferences("namefile", Context.MODE_PRIVATE); (use Shared Preferences in Fragment)*/ String getValueFromKey = sharedPreferences.getString("yourKey",new String()); //Log.d("printf:",getValueFromKey ); getValueFromKey ="Hahaha"; /* Edit value or Do nothing …… */ SharedPreferences.Editor editor = sharedPreferences.edit(); editor.clear(); //[important] Clearing your editor before using it. editor.putString("yourKey", getValueFromKey); editor.commit();
Solution 2:
SharedPreferences sharedPreferences = getSharedPreferences("namefile", Context.MODE_PRIVATE);//store or retrieved file "namefile.xml". /*or SharedPreferences sharedPreferences = getActivity().getSharedPreferences("namefile", Context.MODE_PRIVATE); (use Shared Preferences in Fragment) */ Set<String> getListValueFromKey = sharedPreferences.getStringSet("yourKey",new HashSet<String>()); getListValueFromKey.add("Hahaha"); getListValueFromKey.add("Kakaka"); getListValueFromKey.add("Hohoho"); /* Add value or Do nothing …… */ SharedPreferences.Editor editor = sharedPreferences.edit(); editor.clear(); //[important] Clearing your editor before using it. editor.putStringSet("yourKey", getListValueFromKey); editor.commit();
I have had exactly same problem like yours and this worked for me. For my whole code sample see
回答3:
Change to:
SharedPreferences emailLoginSP;
SharedPreferences.Editor SPEdit;
emailLoginSP = getSharedPreferences("pref_file_name",MODE_PRIVATE);
SPEdit = emailLoginSP.edit();
SPEdit.putString("prefEmailId", email_text);
SPEdit.putString("prefUserId", userIDToken);
SPEdit.putString("prefAccess_token", accessToken);
SPEdit.commit();
NOTE: This is untested and from memory, so there may be an error.
You want to minimise the .commit() calls, which is why there is only one at the end.
pref_file_name can be whatever you want, with lower case letters, no numbers at start, etc.
回答4:
See I have done like below.
sharedPreferences = PreferenceManager
.getDefaultSharedPreferences(getApplicationContext());
editor = sharedPreferences.edit();
isPaidVerison = sharedPreferences.getInt("isPaidVerison", 0);
editor.putInt("isPaidVerison", 1);
editor.commit();
And this works fine. Data will remain in Sharedprefrences till will do not reinstall the app or till will d'not clear data.
And I retrive data this way.
isPaidVerison = sharedPreferences.getInt("isPaidVerison", 0);
回答5:
Make sure that you are using the same file to save and retrieve. This made me look really dumb :(
// When saving
public SharedPreferences.Editor getEditor(Activity activity, int mode) {
SharedPreferences sharedPref = activity.getApplicationContext().getSharedPreferences(PreferenceConstants.SWAGGER_USER_PREFS, mode);
SharedPreferences.Editor editor = sharedPref.edit();
return editor;
}
// When getting it
public SharedPreferences getSharedPref(Activity activity, int mode) {
SharedPreferences sharedPref = activity.getSharedPreferences(PreferenceConstants.SWAGGER_USER_PREFS, mode);
return sharedPref;
}
回答6:
If you want to try an approach other than shared preferences then you can use a file to write the values and then retrieve the values from it. Declare a text file emailLogin.txt and use it as follows to write the data.
try {
Context context = MainActivity.this;
OutputStreamWriter out=
new OutputStreamWriter(context.openFileOutput(EMAILLOGIN, 0));
out.write(email_text);
out.write("\r\n");
out.write(userIDToken);
out.write("\r\n");
out.write(accessToken);
out.write("\r\n");
out.close();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
After writing to the file, you can do the following to read from it.
File file = this.getFileStreamPath(EMAILLOGIN);
if(file.exists())
{
try {
InputStream in=openFileInput(NUMBERS);
if (in!=null) {
InputStreamReader tmp=new InputStreamReader(in);
BufferedReader reader=new BufferedReader(tmp);
String str;
String strcount[]= new String[20];
java.util.Arrays.fill(strcount, 0, 10, "");
while ((str = reader.readLine()) != null) {
strcount[linecount]=str;
}
loginEmail = strcount[0];
loginUserId = strcount[1];
loginAccessToken = strcount[2];
in.close();
}
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
This will ensure that even when your app force closes or if your device reboots, you can still read the required values from the file.
来源：https://stackoverflow.com/questions/15353900/shared-preferences-reset-data-when-app-is-force-closed-or-device-is-restarted