Develop Reference

Why does the getBoolean always return default?

I'm using SharedPreferences to store the value of multiple checkboxes and some strings, and it's doing well. When I try to use it to store the value of a switch it doesn't work, and keep getting the default value.
I initialize like this
SharedPreferences.Editor editor;
SharedPreferences prefs;
I put this on "onCreate"
editor = getSharedPreferences(FirstStart.MY_PREFS_NAME, MODE_PRIVATE).edit();
prefs = getSharedPreferences(FirstStart.MY_PREFS_NAME, MODE_PRIVATE);
And then I'm testing it on the "onClick" event of the switch (I'm using toasts to test)
public void clickSwitchAlarm(View view) {
editor.putBoolean("swAlarma", swAlarm.isChecked());
Toast.makeText(MainMenu.this, "isChecked() value: " + swAlarm.isChecked(), Toast.LENGTH_SHORT).show();
//Toast.makeText(MainMenu.this, "getBoolean value: " + prefs.getBoolean("swAlarma", false), Toast.LENGTH_SHORT).show();
}
When I check the "isChecked()" value it works fine, but when I check the SharedPreferences stored value it shows the default.
Does anybody know what's happening here? Thank you!
(Working with API15)

After putting the value inside the editor, you must confirm the operation by calling commit() or apply() method`s :
editor.commit();
//or
editor.apply();
Otherwise your operation will not be validated and the value will not be saved.

How can I know that Android SharedPreferences are saved successfully?

I am saving some data to SharedPreference from a fragment and want use these data in other fragments. But I want to perform fragment transaction only if SharedPreferences are saved successfully, otherwise, other fragments would not be able to retrieve data (since using those SharedPreference values to retrieve data).
My code:
public class MainActivity extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener{
... ... ... ... ... ... ... ... ...
public void setSharedPref(String key, String val) {
SharedPreferences sharedPref = this.getPreferences(Context.MODE_PRIVATE);
SharedPreferences.Editor editor = sharedPref.edit();
editor.putString(key, val);
editor.commit();
}
public String fetchSharedPref(String key) {
SharedPreferences sharedPref = this.getPreferences(Context.MODE_PRIVATE);
String val = sharedPref.getString(key, Constant.SHARED_PREF_DEFAULT_MSN);
return val;
}
}
How can I be sure that SharedPreferences are saved successfully?
Is there any way to implement a callback that will be invoked only if SharedPreferences saved successfully?

From the docs.
SharedPreferences sharedPref = getActivity().getPreferences(Context.MODE_PRIVATE);
SharedPreferences.Editor editor = sharedPref.edit();
editor.putInt(getString(R.string.saved_high_score), newHighScore);
editor.commit();
Then go and check commit() method here.
Return type: boolean
Description: Returns true if the new values were successfully written to persistent storage.

Find the solution :
SharedPreferences sharedPref = getActivity().getPreferences(Context.MODE_PRIVATE);
SharedPreferences.Editor editor = sharedPref.edit();
editor.putInt("Your Key", "Your value");
boolean savedOrNot = editor.commit();
if(savedOrNot){
// Successfully saved
}else{
// Not saved
}

Form Documentation
apply()
This saves your data into memory immediately and saves the data to
disk on a separate thread. So there is no chance of blocking the main
thread (your app won’t hang).
It is the preferred technique but has only been available since
Gingerbread (API 9, Android 2.3).
commit()
Calling this will save the data to the file however, the process is
carried out in the thread that called it, stopping everything else
until the save is complete. It returns true on successful completion,
false on failure.
Use commit() if you need confirmation of the success of saving your
data or if you are developing for pre-Gingerbread devices. commit()
has been available since API 1
so your can check status at editor.commit();
commit() returns true if the save works, false otherwise.

commit() returns true if the save works, false otherwise.
You can alter your method as follows.
public boolean setSharedPref(String key, String val) {
SharedPreferences sharedPref = this.getPreferences(Context.MODE_PRIVATE);
SharedPreferences.Editor editor = sharedPref.edit();
editor.putString(key, val);
return editor.commit()
}
Difference between apply and commit https://developer.android.com/reference/android/content/SharedPreferences.Editor.html

The editor.commit() will return boolean value , which will let you know if data has been saved.
If you would like to analyze all the data saved in shared preferences and sqlite ,then i would recommend using facebook stetho
Its a debug bridge for android , you can check all of your shared preferences data and sql databases for debugging.

Shared Preferences in Android?

I'm a novice Android developer who are currently trying hard to build a Login Screen.
I need to find the easiest way to store the username and password in 1 class and retrieve it from another class. See Google has provided several ways: http://developer.android.com/guide/topics/data/data-storage.html
which one is the most efficient and easy to code?
thanks!

For Login screen tasks like storing username and password you can use Shared Preferences. Here I had made custom methods for using shared preferences. Call savePreferences() method and put your Key and Value(as savePreferences() is based on XML), similarly call Load with your Key. And lastly don't forgot to call deletePreferences() on LOGOUT.
/**
* Method used to get Shared Preferences */
public SharedPreferences getPreferences()
{
return getSharedPreferences(<PREFRENCE_FILE_NAME>, MODE_PRIVATE);
}
/**
* Method used to save Preferences */
public void savePreferences(String key, String value)
{
SharedPreferences sharedPreferences = getPreferences();
SharedPreferences.Editor editor = sharedPreferences.edit();
editor.putString(key, value);
editor.commit();
}
/**
* Method used to load Preferences */
public String loadPreferences(String key)
{
try {
SharedPreferences sharedPreferences = getPreferences();
String strSavedMemo = sharedPreferences.getString(key, "");
return strSavedMemo;
} catch (NullPointerException nullPointerException)
{
Log.e("Error caused at TelaSketchUtin loadPreferences method",
">======>" + nullPointerException);
return null;
}
}
/**
* Method used to delete Preferences */
public boolean deletePreferences(String key)
{
SharedPreferences.Editor editor=getPreferences().edit();
editor.remove(key).commit();
return false;
}

Define some statics to store the preference file name and the keys you're going to use:
public static final String PREFS_NAME = "MyPrefsFile";
private static final String PREF_USERNAME = "username";
private static final String PREF_PASSWORD = "password";
You'd then save the username and password as follows:
getSharedPreferences(PREFS_NAME,MODE_PRIVATE)
.edit()
.putString(PREF_USERNAME, username)
.putString(PREF_PASSWORD, password)
.commit();
So you would retrieve them like this:
SharedPreferences pref = getSharedPreferences(PREFS_NAME,MODE_PRIVATE);
String username = pref.getString(PREF_USERNAME, null);
String password = pref.getString(PREF_PASSWORD, null);
if (username == null || password == null) {
//Prompt for username and password
}
Alternatively, if you don't want to name a preferences file you can just use the default:
SharedPreferences pref = PreferenceManager.getDefaultSharedPreferences(this);

For your purpose both, SQLite Database and SharedPreferences will work. But I would suggest SharedPreferences as they are very easy to use. Some ppl like to create a class to hold variables like this but the benefit of SQLite and SharedPreferences file is that the user login name and password information will be with you even if the app goes in background and gets destroyed. So when the user comes back to your app, you can sign them in again without asking for password. If user explicitly decides to logout, you can simply remove the login information from shared preferences file

The easiest way of retrieving log in information from other activities is using "SharedPreferences". I strongly recommend this method for storage and retrieval of Username and Password. Because you can access this information from anywhere in the application without any complications. The log in information may have to use repeatedly in an application.

Many applications may provide a way to capture user preferences on the settings of a specific application or an activity. For supporting this, Android provides a simple set of APIs.
Preferences are typically name value pairs. They can be stored as “Shared Preferences” across various activities in an application (note currently it cannot be shared across processes). Or it can be something that needs to be stored specific to an activity.
Shared Preferences: The shared preferences can be used by all the components (activities, services etc) off the applications.
Activity handled preferences: These preferences can only be used with in the activity and can not be used by other components of the application.
Shared Preferences:
The shared preferences are managed with the help of the getSharedPreferences method of the Context class. The preferences are stored in a default file(1) or you can specify a file name(2) to be used to refer to the preferences.
(1) Here is how you get the instance when you specify the file name
public static final String PREF_FILE_NAME = "PrefFile";
SharedPreferences preferences = getSharedPreferences(PREF_FILE_NAME, MODE_PRIVATE);
MODE_PRIVATE is the operating mode for the preferences. It is the default mode and means the created file will be accessed by only the calling application. Other two mode supported are MODE_WORLD_READABLE and MODE_WORLD_WRITEABLE. In MODE_WORLD_READABLE other application can read the created file but can not modify it. In case of MODE_WORLD_WRITEABLE other applications also have write permissions for the created file.
(2) The recommended way is to use by the default mode, without specifying the file name:
SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(context);
Finally, once you have the preferences instance, here is how you can retrieve the stored values from the preferences:
int storedPreference = preferences.getInt("storedInt", 0);
To store values in the preference file SharedPreference.Editor object has to be used. Editor is the nested interface of the SharedPreference class.
SharedPreferences.Editor editor = preferences.edit();
editor.putInt("storedInt", storedPreference); // value to store
editor.commit();
Editor also support methods like remove() and clear() to delete the preference value from the file.
Activity Preferences:
The shared preferences can be used by other application components. But if you do not need to share the preferences with other components and want to have activities private preferences. You can do that with the help of getPreferences() method of the activity. The getPreference method uses the getSharedPreferences() method with the name of the activity class for the preference file name.
Following is the code to get preferences:
SharedPreferences preferences = getPreferences(MODE_PRIVATE);
int storedPreference = preferences.getInt("storedInt", 0);
The code to store values is also same as in case of shared preferences.
SharedPreferences preferences = getPreference(MODE_PRIVATE);
SharedPreferences.Editor editor = preferences.edit();
editor.putInt("storedInt", storedPreference); // value to store
editor.commit();
You can also use other methods like storing the activity state in database. Note Android also contains a package called android.preference. The package defines classes to implement application preferences UI.
To see some more examples check Android's Data Storage post on developers site.
For more info, check this link:
Making data persistent in android

Android: How to check does shared preferences exist, and how to delete them

To check does preferences exist I tried this way, but it shows null every time(maybe because I saved preferences in different view):
String def = null;
String test = getPreferences(MODE_PRIVATE).getString(PREF_GAME,def);
if(test == null) Log.v("main", "no saved data");
To delete preferences I tried editor.clear(), but it does't delete (however commit() every time return true):
SharedPreferences preferences = getSharedPreferences(PREF_GAME,MODE_PRIVATE);
SharedPreferences.Editor editor = preferences.edit();
editor.clear();
boolean tt = editor.commit();Log.v("DELETE PREF", String.valueOf(tt));
UPDATE: I found that if I check preferences exist in the same view, where i saved it, this checking works fine, but how can i do this in different view?
Update: I guessed with myself, thanks everyone!

Use getSharedPreferences() to get your preference.
getSharedPreferences() - Use this if you need multiple preferences files identified by name, which you specify with the first parameter.
getPreferences() - Use this if you need only one preferences file for your Activity. Because this will be the only preferences file for your Activity, you don't supply a name.

This is my code:
public String prefGet(String id) {
SharedPreferences opener = getPreferences(MODE_PRIVATE);
String value = opener.getString(id, "Default");
return value;

Android - How Do I Set A Preference In Code

I have an Android application in which I have my preferences in an XML file, which works fine. I now want to set one of the preferences using code instead of displaying the entire preference screen, how would I go about doing this?

I assume by preferences you are referring to your application's preferences and not Android phone settings.
To store preferences between runs of you application you need to do the following
Create a SharedPreferences object
SharedPreferences settings = getSharedPreferences(String n, MODE_PRIVATE);
String n identifies your preferences and the second argument is the mode they'll be accessed
Instantiate an Editor object
SharedPreferences.Editor editor = settings.edit();
Note: do not try settings.editor.edit(), this will not make a persistent object and the code below will not work
Write your preferences to the buffer
editor.put...(String, value)
There are numerous put function, putString, putBoolean, etc. The String is the key ("version", "good run") and the value is the value ("1.5.2", true)
Flush the buffer
editor.commit();
This actually writes you put to the preferences. If your app crashes before this line then the preferences will not be written. There is also a documented bug: commit() is supposed to return a boolean indicating success or failure. Last I checked it always returned false.
These preferences will by stored on the phone and will only be accessible to your application.
More documentation is here

I tried this but didn't work:
SharedPreferences settings = getSharedPreferences(String n, MODE_PRIVATE);
Try this instead:
SharedPreferences settings = PreferenceManager.getDefaultSharedPreferences(this);

You can save something in the sharedpreferences by using below code
public static void save(String valueKey, String value) {
SharedPreferences prefs = PreferenceManager
.getDefaultSharedPreferences(context);
SharedPreferences.Editor edit = prefs.edit();
edit.putString(valueKey, value);
edit.commit();
}
To read preferences:
public static String read(String valueKey, String valueDefault) {
SharedPreferences prefs = PreferenceManager
.getDefaultSharedPreferences(context);
return prefs.getString(valueKey, valueDefault);
}