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

public class VcareSharedPreference {
  private static VcareSharedPreference sharePref = new VcareSharedPreference(); 
  private static SharedPreferences sharedPreferences; 
  private static SharedPreferences.Editor editor;
  private VcareSharedPreference() {
 } 
public static VcareSharedPreference getInstance(Context context) {
    if (sharedPreferences == null) {
        sharedPreferences = context.getSharedPreferences(context.getPackageName(), Activity.MODE_PRIVATE);
        editor = sharedPreferences.edit();
    }
    return sharePref;
 }
public void save(String KEY, String text) {
    editor.putString(KEY, text);
    editor.commit();
}
 public String getValue(String PREFKEY) {
    String text;

    //settings = PreferenceManager.getDefaultSharedPreferences(context);
    text = sharedPreferences.getString(PREFKEY, null);
    return text;
}
public void removeValue(String KEY) {
    editor.remove(KEY);
    editor.commit();
}

public void clearAll() {
    editor.clear();
    editor.commit();
}
public void saveArrayList(String key, ArrayList<ModelWelcome> modelCourses) {
    Gson gson = new Gson();
    String json = gson.toJson(modelCourses);
    editor.putString(key, json);
    editor.apply();
}

public ArrayList<ModelWelcome> getArray(String key) {

    Gson gson = new Gson();
    String json = sharedPreferences.getString(key, null);
    Type type = new TypeToken<ArrayList<ModelWelcome>>() {
    }.getType();
 return gson.fromJson(json, type);}}

其他回答

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。

该方法用于存储/保存数组列表:-

 public static void saveSharedPreferencesLogList(Context context, List<String> collageList) {
            SharedPreferences mPrefs = context.getSharedPreferences("PhotoCollage", context.MODE_PRIVATE);
            SharedPreferences.Editor prefsEditor = mPrefs.edit();
            Gson gson = new Gson();
            String json = gson.toJson(collageList);
            prefsEditor.putString("myJson", json);
            prefsEditor.commit();
        }

该方法用于检索数组列表:-

public static List<String> loadSharedPreferencesLogList(Context context) {
        List<String> savedCollage = new ArrayList<String>();
        SharedPreferences mPrefs = context.getSharedPreferences("PhotoCollage", context.MODE_PRIVATE);
        Gson gson = new Gson();
        String json = mPrefs.getString("myJson", "");
        if (json.isEmpty()) {
            savedCollage = new ArrayList<String>();
        } else {
            Type type = new TypeToken<List<String>>() {
            }.getType();
            savedCollage = gson.fromJson(json, type);
        }

        return savedCollage;
    }

请在kotlin中使用这两种方法将数据存储在ArrayList中

fun setDataInArrayList(list: ArrayList<ShopReisterRequest>, key: String, context: Context) {
    val prefs = PreferenceManager.getDefaultSharedPreferences(context)
    val editor = prefs.edit()
    val gson = Gson()
    val json = gson.toJson(list)
    editor.putString(key, json)
    editor.apply()   
}

fun getDataInArrayList(key: String, context: Context): ArrayList<ShopReisterRequest> {
    val prefs = PreferenceManager.getDefaultSharedPreferences(context)
    val gson = Gson()
    val json = prefs.getString(key, null)
    val type = object : TypeToken<ArrayList<ShopReisterRequest>>() {

    }.type
    return gson.fromJson<ArrayList<ShopReisterRequest>>(json, type)
}  
//Set the values
intent.putParcelableArrayListExtra("key",collection);

//Retrieve the values
ArrayList<OnlineMember> onlineMembers = data.getParcelableArrayListExtra("key");

使用这个自定义类:

public class SharedPreferencesUtil {

    public static void pushStringList(SharedPreferences sharedPref, 
                                      List<String> list, String uniqueListName) {

        SharedPreferences.Editor editor = sharedPref.edit();
        editor.putInt(uniqueListName + "_size", list.size());

        for (int i = 0; i < list.size(); i++) {
            editor.remove(uniqueListName + i);
            editor.putString(uniqueListName + i, list.get(i));
        }
        editor.apply();
    }

    public static List<String> pullStringList(SharedPreferences sharedPref, 
                                              String uniqueListName) {

        List<String> result = new ArrayList<>();
        int size = sharedPref.getInt(uniqueListName + "_size", 0);

        for (int i = 0; i < size; i++) {
            result.add(sharedPref.getString(uniqueListName + i, null));
        }
        return result;
    }
}

使用方法:

SharedPreferences sharedPref = getPreferences(Context.MODE_PRIVATE);
SharedPreferencesUtil.pushStringList(sharedPref, list, getString(R.string.list_name));
List<String> list = SharedPreferencesUtil.pullStringList(sharedPref, getString(R.string.list_name));