如何将哈希图保存到共享首选项？

Question

I want to save a hashmap to shared preference . The keys of hashmap will be ipaddresses and values will be flags(like true or false). To display the ipaddreeses to user I have to get all the keys of hashmap. And whenever i want to display the flag value i have to get it using ipaddress key.I do not want to use a separate shared preferences or file for this. How can i do this?

Answer 1

Try this to save objects in SharedPreferences.

you need to add Gson library to your project.

public void putMyObject(String key , Object obj) {

        //AnyVehicleModel mvehicle  =new AnyVehicleModel();
        SharedPreferences.Editor editor = preferences.edit();
        Gson gson = new Gson();
        String json = gson.toJson(obj);
        editor.putString(key,json);
        editor.apply();
    }




    public MyObject getMyObject(String key) {

        Gson gson = new Gson();
        String json = preferences.getString(key,"");
        MyObject obj = gson.fromJson(json, MyObject.class);
        if (obj== null){return new MyObject ();}
        return obj;

    }

Answer 2

You can save it as an object or convert it to JSON and save it:

store and retrieve a class object in shared preference

This might be helpful also:

How Android SharedPreferences save/store object

It explains how to convert an object to JSON that you can save with SharedPreferences and retrieve/rebuild.

Answer 3

with Kotlin it would be like this:

fun saveUserInfoMap(userInfo: HashMap<String, Any>){
    val prefs = PreferenceManager
        .getDefaultSharedPreferences(App.appContext)
    val gson = Gson()
    val editor = prefs.edit()
    val json = gson.toJson(userInfo)
    editor.putString("user_info", json)
    editor.apply()
}

@Suppress("UNCHECKED_CAST")
fun getUserInfoMap(): HashMap<String, Any>? {
    val prefs = PreferenceManager
        .getDefaultSharedPreferences(App.appContext)
    val gson = Gson()
    val json = prefs.getString("user_info", "")
    val typeToken = object: TypeToken<HashMap<String, Any>>(){}
    var obj: HashMap<String, Any> = HashMap()
    if (!TextUtils.isEmpty(json)) {
        obj = gson.fromJson<Any>(json, typeToken.type) as HashMap<String, Any>
    }
    return obj
}