Android Shared Preference

codemonkeyalx

Does anyone know the call for android shared preferences?

TomOpgenorth

You'll want to get an instance of ISharedPreferences and use that to update/change/delete preferences. There are a couple of ways to get an instance of ISharedPreferences:

1. Activity.GetPreferences would get you preferences specific to that activity. Probably not what you want.
2. Context.GetSharedPreferences can get you application level preferences.
3. PreferenceManager.DefaultSharedPreferences will give you an ISharedPreference instance for a given context.

The actual saving is done by an instance of ISharedPreferencesEditor, which you get get by invoking the method ISharedPreferencesEditor.Edit().

Here's a quick example:

// this is an Activity
ISharedPreferences prefs = PreferenceManager.GetDefaultSharedPreferences(this); 
ISharedPreferencesEditor editor = prefs.Edit();
editor.PutInt(("number_of_times_accessed", accessCount++);
editor.PutString("date_last_accessed", DateTime.Now.ToString("yyyy-MMM-dd"));
editor.Apply();

You can use the PreferenceActivity (pre Honeycomb) or the PreferenceFragment (Honeycomb and higher) to handle a lot of the work surrounding displaying and editing preferences.

codemonkeyalx

Thank you for your input! - it helped set me on the right track!

Robin

As the android.app.Application class inherits from android.content.Context, I should be able to use the Application class in:
PreferenceManager.GetDefaultSharedPreferences(MyAppObject);
However, storing or reading preferences from the instance of ISharedPreferences obtained this way does not work. In a native android app this does work. When I pass in an activity context, everything works as expected. I think this is a bug.

Cheesebaron

Try using ApplicationContext instead.

Robin

I see the same behaviour when using MyAppObject or MyAppObject.ApplicationContext

This is in my application class:

    static MyApplication _instance;

    public MyApplication(IntPtr handle, JniHandleOwnership transfer): 
        base(handle, transfer)
    {
        _instance = this;
    }

    public static MyApplication Instance
    {
        get { return _instance; }
    }

And this is is my preferences class:

    const string MyPrefKey = "my-pref-key";

    static ISharedPreferences Prefs
    {
        get
        {
            return PreferenceManager.GetDefaultSharedPreferences(
                MyApplication.Instance.ApplicationContext); 
        }
    }

    static ISharedPreferencesEditor Editor
    {
        get
        {
            return Prefs.Edit();
        }
    }

    public static string MyPref
    {
        get
        {
            return Prefs.GetString(MyPrefKey, null);
        }
        set
        {
            Editor.PutString(MyPrefKey, value);
            Editor.Commit();
        }
    }

As this is more or less one-to-one translation of working native code, I don't see why this isn't working. With not working I mean Editor.Commit returns true (so writing is successful), but reading MyPref always returns null, the default. Again, using an activity as context does work.

Greenius

Hi Robin,

I had exactly the same problem. The value of (this) changes every time I run the app, so no prefs are ever found by ISharedPreferences prefs = PreferenceManager.GetDefaultSharedPreferences(this);

I can get it to work like this:

var c = (Context)this;

ISharedPreferences prefs = c.GetSharedPreferences ("SimpleTest", FileCreationMode.WorldReadable);

My code is never going into production so I'm happy with the WorldReadable FileCreationMode, but of course you could go for something more sensible like Private or MultiProcess instead.

JuanCarlosUsquiano

does it work now days?

SebastianSeidel.9226

Yes.

modernsl4ve

I know this is super old, but in case anyone runs into problems:

I initially used the same approach as Robin above (i.e: getting the Editor from a singleton App instance).
The problem with this is that you are re-invoking GetDefaultSharedPreferences() each time you access the Editor property, which means your edits won't get saved even if you're calling commit!

So this:
App.Prefs.Edit().PutInt( GetString( Resource.String.pref_calendarId_int ), calId ); App.Prefs.Edit().Commit();

doesn't work, while this:
var editor = App.Prefs.Edit(); editor.PutInt( GetString( Resource.String.pref_calendarId_int ), calId ); editor.Commit();

DOES work! Sounds strange, I know, but that's what worked for me..

aquabay

Something like this should work:

public class AppPreferences : ISharedPreferences, ISharedPreferencesEditor
{
private ISharedPreferences mSharedPrefs;
private ISharedPreferencesEditor mPrefsEditor;
private Context mContext;

    #region ISharedPreferences impl
    public IDictionary<string, object> All
    {
        get
        {
            return mSharedPrefs.All;
        }
    }

    public IntPtr Handle
    {
        get
        {
            return mSharedPrefs.Handle;
        }
    }

    public AppPreferences(Context context)
    {
        this.mContext = context;
        mSharedPrefs = PreferenceManager.GetDefaultSharedPreferences(mContext);
        mPrefsEditor = mSharedPrefs.Edit();
    }

    public bool Contains(string key)
    {
        throw new NotImplementedException();
    }

    public ISharedPreferencesEditor Edit()
    {
        throw new NotImplementedException();
    }

    public string GetString(string key, string defValue)
    {
        return mSharedPrefs.GetString(key, defValue);
    }

    public bool GetBoolean(string key, bool defValue)
    {
        return mSharedPrefs.GetBoolean(key, defValue);
    }

    public float GetFloat(string key, float defValue)
    {
        return mSharedPrefs.GetFloat(key, defValue);
    }

    public int GetInt(string key, int defValue)
    {
        return mSharedPrefs.GetInt(key, defValue);
    }

    public long GetLong(string key, long defValue)
    {
        return mSharedPrefs.GetLong(key, defValue);
    }

    public ICollection<string> GetStringSet(string key, ICollection<string> defValues)
    {
        return mSharedPrefs.GetStringSet(key, defValues);
    }

    public void RegisterOnSharedPreferenceChangeListener(ISharedPreferencesOnSharedPreferenceChangeListener listener)
    {
        mSharedPrefs.RegisterOnSharedPreferenceChangeListener(listener);
    }

    public void UnregisterOnSharedPreferenceChangeListener(ISharedPreferencesOnSharedPreferenceChangeListener listener)
    {
        mSharedPrefs.UnregisterOnSharedPreferenceChangeListener(listener);
    }

    public void Dispose()
    {
        mSharedPrefs.Dispose();
    }
    #endregion

    #region ISharedPreferencesEditor impl
    public void Apply()
    {
        mPrefsEditor.Apply();
    }

    public ISharedPreferencesEditor Clear()
    {
        return mPrefsEditor.Clear();
    }

    public bool Commit()
    {
        return mPrefsEditor.Commit();
    }

    public ISharedPreferencesEditor PutBoolean(string key, bool value)
    {
        return mPrefsEditor.PutBoolean(key, value);
    }

    public ISharedPreferencesEditor PutFloat(string key, float value)
    {
        return mPrefsEditor.PutFloat(key, value);
    }

    public ISharedPreferencesEditor PutInt(string key, int value)
    {
        return mPrefsEditor.PutInt(key, value);
    }

    public ISharedPreferencesEditor PutLong(string key, long value)
    {
        return mPrefsEditor.PutLong(key, value);
    }

    public ISharedPreferencesEditor PutString(string key, string value)
    {
        return mPrefsEditor.PutString(key, value);
    }

    public ISharedPreferencesEditor PutStringSet(string key, ICollection<string> values)
    {
        return mPrefsEditor.PutStringSet(key, values);
    }

    public ISharedPreferencesEditor Remove(string key)
    {
        return mPrefsEditor.Remove(key);
    }
    #endregion
}

GaryParkin

Thank you from me too! This is a huge help.
I really want to save it to a SQLite database but I didn't think I had time before the app crashes or gets killed from memory.

MomenMagdi

when i finish to use sharedPreferance and stop run an run another time the sharedPreferance Save the old value i need help