How do I use SharedPreferences in Xamarin.Android?

问题

I want to save and retrieve some application settings in my Xamarin.Android project.

I know that in Android (java), I use the class SharedPreferences to store this information, but I do not know how to convert that to Xamarin C#.

When I type "SharedPreferences" into the Xamarin Studio IDE, there is no auto-completion, so I don't know what to use.

An initial search of the interwebs took me to a related question, but only contains Android java:

Use Shared Preferences in xamarin

So to summarise:

What is the Xamarin Android C# equivalent of Android Java's SharedPreferences?

回答1:

The Xamarin.Android equivalent of SharedPreferences is an interface called ISharedPreferences.

Use it in the same way, and you will be able to easily port Android code across.

For example, to save a true/false bool using some Context you can do the following:

ISharedPreferences prefs = PreferenceManager.GetDefaultSharedPreferences (mContext);
ISharedPreferencesEditor editor = prefs.Edit ();
editor.PutBoolean ("key_for_my_bool_value", mBool);
// editor.Commit();    // applies changes synchronously on older APIs
editor.Apply();        // applies changes asynchronously on newer APIs

Access saved values using:

ISharedPreferences prefs = PreferenceManager.GetDefaultSharedPreferences (mContext);
mBool = prefs.GetBoolean ("key_for_my_bool_value", <default value>);
mInt = prefs.GetInt ("key_for_my_int_value", <default value>);
mString = prefs.GetString ("key_for_my_string_value", <default value>);

From this sample, you can see that once you know the correct C# interface to use, the rest is easy. There are many Android java examples on how to use SharedPreferences for more complex situations, and these can be ported very easily using ISharedPreferences.

For more information, read this thread:

Android Shared Preference on Xamarin forum

回答2:

You can use this example for you SharedPreferences in Xamarin.Android

First, you need to use :

ISharedPreferences //Interface for accessing and modifying preference data
ISharedPreferencesEditor // Interface used for modifying values in a ISharedPreferences

You can create a similar class

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

    private static String PREFERENCE_ACCESS_KEY = "PREFERENCE_ACCESS_KEY";

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

    public void saveAccessKey(string key){
        mPrefsEditor.PutString(PREFERENCE_ACCESS_KEY, key);
        mPrefsEditor.Commit();
    }

    public string getAccessKey(){
        return mSharedPrefs.GetString(PREFERENCE_ACCESS_KEY, "");
    }
}

From the Activity.

Context mContext = Android.App.Application.Context;
AppPreferences ap = new AppPreferences (mContext);

If you want to save some value:

string key = "123123";
ap.saveAccessKey (key);

If you want to get the value

string key = ap.getAccessKey();

I hope this example helps you

回答3:

I had trouble using PreferenceManager as the example shows. I added this code at the top and now I'm good using it.

using Android.Preferences;

Plus to get the preferences you have to add the default value as a second parameter or it will not compile

mInt = prefs.GetInt ("key_for_my_int_value", defaultInt);

回答4:

Not sure if you still dont know or not, but make sure you Dispose your variables if they are inside a function:

prefs.Dispose();
prefEditor.Dispose();

I had a crash/freeze on my app over some time because of not disposing the memory whenever it is not needed anymore.

来源：https://stackoverflow.com/questions/26668509/how-do-i-use-sharedpreferences-in-xamarin-android

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android

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