I have an ArrayList with custom objects. Each custom object contains a variety of strings and numbers. I need the array to stick around even if the user leaves the activity and then wants to come back at a later time, however I don't need the array available after the application has been closed completely. I save a lot of other objects this way by using the SharedPreferences but I can't figure out how to save my entire array this way. Is this possible? Maybe SharedPreferences isn't the way to go about this? Is there a simpler method?


当前回答

别忘了实现Serializable:

Class dataBean implements Serializable{
 public String name;
}
ArrayList<dataBean> dataBeanArrayList = new ArrayList();

https://stackoverflow.com/a/7635154/4639974

其他回答

我的utils类保存列表到SharedPreferences

public class SharedPrefApi {
    private SharedPreferences sharedPreferences;
    private Gson gson;

    public SharedPrefApi(Context context, Gson gson) {
        this.sharedPreferences = context.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE);
        this.gson = gson;
    } 

    ...

    public <T> void putList(String key, List<T> list) {
        SharedPreferences.Editor editor = sharedPreferences.edit();
        editor.putString(key, gson.toJson(list));
        editor.apply();
    }

    public <T> List<T> getList(String key, Class<T> clazz) {
        Type typeOfT = TypeToken.getParameterized(List.class, clazz).getType();
        return gson.fromJson(getString(key, null), typeOfT);
    }
}

使用

// for save
sharedPrefApi.putList(SharedPrefApi.Key.USER_LIST, userList);

// for retrieve
List<User> userList = sharedPrefApi.getList(SharedPrefApi.Key.USER_LIST, User.class);

. 我的utils的完整代码//检查使用实例的活动代码

我已经阅读了上面所有的答案。这都是正确的,但我找到了一个更简单的解决方案如下:

Saving String List in shared-preference>> public static void setSharedPreferenceStringList(Context pContext, String pKey, List<String> pData) { SharedPreferences.Editor editor = pContext.getSharedPreferences(Constants.APP_PREFS, Activity.MODE_PRIVATE).edit(); editor.putInt(pKey + "size", pData.size()); editor.commit(); for (int i = 0; i < pData.size(); i++) { SharedPreferences.Editor editor1 = pContext.getSharedPreferences(Constants.APP_PREFS, Activity.MODE_PRIVATE).edit(); editor1.putString(pKey + i, (pData.get(i))); editor1.commit(); } } and for getting String List from Shared-preference>> public static List<String> getSharedPreferenceStringList(Context pContext, String pKey) { int size = pContext.getSharedPreferences(Constants.APP_PREFS, Activity.MODE_PRIVATE).getInt(pKey + "size", 0); List<String> list = new ArrayList<>(); for (int i = 0; i < size; i++) { list.add(pContext.getSharedPreferences(Constants.APP_PREFS, Activity.MODE_PRIVATE).getString(pKey + i, "")); } return list; }

这里的常数。APP_PREFS是要打开的文件的名称;不能包含路径分隔符。

使用Kotlin,对于简单的数组和列表,你可以这样做:

class MyPrefs(context: Context) {
    val prefs = context.getSharedPreferences("x.y.z.PREFS_FILENAME", 0)
    var listOfFloats: List<Float>
        get() = prefs.getString("listOfFloats", "").split(",").map { it.toFloat() }
        set(value) = prefs.edit().putString("listOfFloats", value.joinToString(",")).apply()
}

然后轻松访问首选项:

MyPrefs(context).listOfFloats = ....
val list = MyPrefs(context).listOfFloats

这应该可以工作:

public void setSections (Context c,  List<Section> sectionList){
    this.sectionList = sectionList;

    Type sectionListType = new TypeToken<ArrayList<Section>>(){}.getType();
    String sectionListString = new Gson().toJson(sectionList,sectionListType);

    SharedPreferences.Editor editor = getSharedPreferences(c).edit().putString(PREFS_KEY_SECTIONS, sectionListString);
    editor.apply();
}

他们,要抓住它才:

public List<Section> getSections(Context c){

    if(this.sectionList == null){
        String sSections = getSharedPreferences(c).getString(PREFS_KEY_SECTIONS, null);

        if(sSections == null){
            return new ArrayList<>();
        }

        Type sectionListType = new TypeToken<ArrayList<Section>>(){}.getType();
        try {

            this.sectionList = new Gson().fromJson(sSections, sectionListType);

            if(this.sectionList == null){
                return new ArrayList<>();
            }
        }catch (JsonSyntaxException ex){

            return new ArrayList<>();

        }catch (JsonParseException exc){

            return new ArrayList<>();
        }
    }
    return this.sectionList;
}

这对我很管用。

public static void WriteSharePrefrence1(Context context, String key, 
ArrayList<HashMap<String, String>> value)
{
    final SharedPreferences preferences = 
    PreferenceManager.getDefaultSharedPreferences(context);
    SharedPreferences.Editor editor = preferences.edit();
    Gson gson = new Gson();
    String json = gson.toJson(value);
    editor.putString(key, json);
    editor.commit();
}
public static ArrayList<HashMap<String, String>> ReadSharePrefrence1(Context context, 
 String key)
{
    String data;
    Gson gson = new Gson();
    ArrayList<HashMap<String, String>> items = new ArrayList<>();
    final SharedPreferences preferences = 
    PreferenceManager.getDefaultSharedPreferences(context);
    final SharedPreferences.Editor editor = preferences.edit();
    data = preferences.getString(key, "");

    Type type = new TypeToken<ArrayList<HashMap<String, String>>>() {}.getType();
    items = gson.fromJson(data, type);

    return items;
}