将arraylist保存在共享首选项中

Question

我将值存储在ArrayList 中并将其传递给使用捆绑包到下一个Fragment，然后我将值设置为我的TextView，直到这里它工作正常，现在转到另一个页面并继续应用程序再回到那个Fragment，我的所有数据都去了，所以我试图将它存储在首选项中，但首选项不允许访问ArrayList，以下是我的代码

 public class Add_to_cart extends Fragment {

    private Button continue_shopping;
    private Button checkout;
    ListView list;
    private TextView _decrease,mBTIncrement,_value;
    private CustomListAdapter adapter;
    private ArrayList<String> alst;
    private ArrayList<String> alstimg;
    private ArrayList<String> alstprc;
    private String bname;
    private ArrayList<String> alsttitle;
    private ArrayList<String> alsttype;

    public static ArrayList<String> static_Alst;
    public Add_to_cart(){}

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {

        final View rootView = inflater.inflate(R.layout.list_view_addtocart, container, false);

        alst=new ArrayList<String>();
        alstimg=new ArrayList<String>();
        Bundle bundle = this.getArguments();
        alst = bundle.getStringArrayList("prducts_id");
        alsttype = bundle.getStringArrayList("prducts_type");
        alstimg=bundle.getStringArrayList("prducts_imgs");
        alsttitle=bundle.getStringArrayList("prducts_title");

        StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
        StrictMode.setThreadPolicy(policy);

        System.out.println("TEst--" + alst);

       // Toast.makeText(getActivity(),"Testing"+alstimg,Toast.LENGTH_LONG).show();
        list=(ListView)rootView.findViewById(R.id.list_addtocart);

        adapter = new CustomListAdapter(getActivity(),alst,alstimg,alsttitle,alsttype);

        list.setAdapter(adapter);
        adapter.notifyDataSetChanged();
        list.setOnItemClickListener(new AdapterView.OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> parent, View view,int position, long id) {
                // TODO Auto-generated method stub
            }
        });
        return rootView;
    }

    public class CustomListAdapter extends BaseAdapter {

        private Context context;
        private ArrayList<String> listData;
        private ArrayList<String> listDataimg;
        private ArrayList<String> listDatatitle;
        private ArrayList<String> listDatatype;
        private AQuery aQuery;
        String dollars="\u0024";

        public CustomListAdapter(Context context,ArrayList<String> listData,ArrayList<String> listDataimg,ArrayList<String> listDatatitle,ArrayList<String> listDatatype) {
            this.context = context;
            this.listData=listData;
            this.listDataimg=listDataimg;
            this.listDatatitle=listDatatitle;
            this.listDatatype=listDatatype;
           aQuery = new AQuery(this.context);
        }

        public void save_User_To_Shared_Prefs(Context context) {
            SharedPreferences appSharedPrefs = PreferenceManager
                    .getDefaultSharedPreferences(context.getApplicationContext());
            SharedPreferences.Editor prefsEditor = appSharedPrefs.edit();
            Gson gson = new Gson();
            String json = gson.toJson(listData);
            Add_to_cart.static_Alst=listData;
            prefsEditor.putString("user", json);
            prefsEditor.commit();
        }

        @Override
        public int getCount() {
            return listData.size();
        }

        @Override
        public Object getItem(int position) {
            return listData.get(position);
        }

        @Override
        public long getItemId(int position) {
            return position;
        }

        @Override
        public View getView(final int position, View convertView, ViewGroup parent) {
            ViewHolder holder;
            if (convertView == null) {
                holder = new ViewHolder();
                convertView = LayoutInflater.from(getActivity()).inflate(R.layout.list_item_addtocart, null);
                holder.propic = (ImageView) convertView.findViewById(R.id.img_addtocart);
                holder.txtproname = (TextView) convertView.findViewById(R.id.proname_addtocart);
                holder.txtprofilecast = (TextView) convertView.findViewById(R.id.proprice_addtocart);
                holder.txtsize = (TextView) convertView.findViewById(R.id.txt_size);
                _decrease = (TextView) convertView.findViewById(R.id.minuss_addtocart);
                mBTIncrement = (TextView) convertView.findViewById(R.id.plus_addtocart);
                _value = (EditText)convertView.findViewById(R.id.edt_procount_addtocart);

                convertView.setTag(holder);
            }else{
                holder = (ViewHolder) convertView.getTag();
            }

            mBTIncrement.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    increment();
                }
            });

            _decrease.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {

                    decrement();
                }
            });

            holder.txtprofilecast.setText(dollars+listData.get(position));
            holder.txtproname.setText(listDatatitle.get(position));
            holder.txtsize.setText(listDatatype.get(position));
            System.out.println("Image ka array " + listDataimg.get(position));

            //Picasso.with(mContext).load(mThumbIds[position]).centerCrop().into(imageView);
            // Picasso.with(context).load(listDataimg.get(position)).into(holder.propic);
            aQuery.id(holder.propic).image(listDataimg.get(position), true, true, 0, R.drawable.ic_launcher);

            return convertView;
        }

        class ViewHolder{
            ImageView propic;
            TextView txtproname;
            TextView txtprofilecast;
            TextView txtsize;
        }
    }
}

Answer 1

sharedpreference中存储和检索arraylist的完整示例：http://blog.nkdroidsolutions.com/arraylist-in-sharedpreferences/

  public void storeFavorites(Context context, List favorites) {
    // used for store arrayList in json format
            SharedPreferences settings;
            Editor editor;
            settings = context.getSharedPreferences(PREFS_NAME,Context.MODE_PRIVATE);
            editor = settings.edit();
            Gson gson = new Gson();
            String jsonFavorites = gson.toJson(favorites);
            editor.putString(FAVORITES, jsonFavorites);
            editor.commit();
        }


        public ArrayList loadFavorites(Context context) {
    // used for retrieving arraylist from json formatted string
            SharedPreferences settings;
            List favorites;
            settings = context.getSharedPreferences(PREFS_NAME,Context.MODE_PRIVATE);
            if (settings.contains(FAVORITES)) {
                String jsonFavorites = settings.getString(FAVORITES, null);
                Gson gson = new Gson();
                BeanSampleList[] favoriteItems = gson.fromJson(jsonFavorites,BeanSampleList[].class);
                favorites = Arrays.asList(favoriteItems);
                favorites = new ArrayList(favorites);
            } else
                return null;
            return (ArrayList) favorites;
        }


        public void addFavorite(Context context, BeanSampleList beanSampleList) {
            List favorites = loadFavorites(context);
            if (favorites == null)
                favorites = new ArrayList();
            favorites.add(beanSampleList);
            storeFavorites(context, favorites);
        }


        public void removeFavorite(Context context, BeanSampleList beanSampleList) {
            ArrayList favorites = loadFavorites(context);
            if (favorites != null) {
                favorites.remove(beanSampleList);
                storeFavorites(context, favorites);
            }
        }

Answer 2

使用 tinydb。检查以下链接，您可能会有所了解。 https://github.com/kcochibili/TinyDB--Android-Shared-Preferences-Turbo

使用 tinydb，您可以将数组存储在本地数据库中。

Answer 3

你可以使用gson：

保存首选项：

 public void save_User_To_Shared_Prefs(Context context, List<User> users) {
        SharedPreferences settings;
        Editor editor;

        settings = context.getSharedPreferences(PREFS_NAME,
                Context.MODE_PRIVATE);
        editor = settings.edit();

        Gson gson = new Gson();
        String jsonUsers = gson.toJson(users);

        editor.putString(USERS, jsonUsers);

        editor.commit();
    }

获取首选项：

public ArrayList<User> getUsers(Context context) {
        SharedPreferences settings;
        List<User> users;

        settings = context.getSharedPreferences(PREFS_NAME,
                Context.MODE_PRIVATE);

        if (settings.contains(USERS)) {
            String jsonUsers = settings.getString(USERS, null);
            Gson gson = new Gson();
            User[] userItems = gson.fromJson(jsonUsers,
                    User[].class);

            users = Arrays.asList(userItems);
            users= new ArrayList<User>(users);
        } else
            return null;

        return (ArrayList<User>) users;
    }

添加用户：

public void addUser(Context context, User user) {
        List<Product> favorites = getUsers(context);
        if (users == null)
            users = new ArrayList<User>();
        users.add(user);
        save_User_To_Shared_Prefs(context, users);
    }

Answer 4

首先从下面的链接下载Gson.jar，然后将其添加到您项目的libs文件夹中

http://www.java2s.com/Code/Jar/g/Downloadgson17jar.htm

然后将 ArrayList 放入 Class 并创建该类的对象，然后您可以将该对象保存到 SharedPreferences，如下所示

public static void save_User_To_Shared_Prefs(Context context, User _USER) {
    SharedPreferences appSharedPrefs = PreferenceManager
            .getDefaultSharedPreferences(context.getApplicationContext());
    SharedPreferences.Editor prefsEditor = appSharedPrefs.edit();
    Gson gson = new Gson();
    String json = gson.toJson(_USER);
    prefsEditor.putString("user", json);
    prefsEditor.commit();

 }

以上代码是一个示例 _USER objext 包含ArrayList。

要阅读对象，请看下面的代码

 public static User get_User_From_Shared_Prefs(Context context) {

    SharedPreferences appSharedPrefs = PreferenceManager
            .getDefaultSharedPreferences(context.getApplicationContext());
    Gson gson = new Gson();
    String json = appSharedPrefs.getString("user", "");


    User user = gson.fromJson(json, User.class);
    return user;
} 

现在，当您想要获取 _USER 对象时，调用上述函数，结果您将拥有该对象，并且您将拥有 ArrayList

Answer 5

另一种解决方案（刚刚想到的）：

如果您有一个名为 addtos 的数组，并且您想将该数组添加到共享首选项中，因为该变量在字典中表示为字符串，您可以将数组索引附加到该字符串的末尾。

例如 -

存储

for(int i = 0; i<addtos.size(); i++)
    prefsEditor.putString("addtos"+i, addtos.get(i));

接收

int i = 0;
while(true){
    if(prefs.getString("addtos"+i, "")!=""){  // or whatever the default dict value is
        // do something with it
        i++;
    }else{break;}
}

我觉得没问题，如果有人发现这有问题，请告诉我。

另外，不需要 ArrayLists