android – 重新启动时保持拖放项目的位置

我有一个RecyclerView – 网格,拖动和使用这个 code我已经设法实现了,并做了很多变化,只有一个问题,我不能保存拖动的项目位置重新启动(应用程序不是手机).
我想到的是在我的item.java构造函数中添加“int position”,但我不能做的就是获得改变的位置.

我正在使用相同的拖放链接中提供的丢弃代码.

itemtouchhelper.Callback _ithCallback = new itemtouchhelper.Callback() {
    //and in your imlpementaion of
    public boolean onMove(RecyclerView recyclerView,RecyclerView.ViewHolder viewHolder,RecyclerView.ViewHolder target) {
        // get the viewHolder's and target's positions in your adapter data,swap them
        Collections.swap(AllItems,viewHolder.getAdapterPosition(),target.getAdapterPosition());
        // and notify the adapter that its dataset has changed

        rcAdapter.notifyItemmoved(viewHolder.getAdapterPosition(),target.getAdapterPosition());
        return true;
    }

    @Override
    public void onSwiped(RecyclerView.ViewHolder viewHolder,int direction) {
        //Todo
    }

    //defines the enabled move directions in each state (idle,swiping,dragging).
    @Override
    public int getMovementFlags(RecyclerView recyclerView,RecyclerView.ViewHolder viewHolder) {
        return makeFlag(itemtouchhelper.ACTION_STATE_DRAG,itemtouchhelper.DOWN | itemtouchhelper.UP | itemtouchhelper.START | itemtouchhelper.END);
    }
};

以下是onCreate中的代码：

itemtouchhelper ith = new itemtouchhelper(_ithCallback);
    ith.attachToRecyclerView(RcView);

更改位置后获取重复的项目,代码：

@Override
public void onStop()
{
    super.onStop();
    SharedPreferencesTools.setorderedItems(this,AllItems);
}

getAllItemList：

private List<Item> getAllItemList(){
AllItems = SharedPreferencesTools.getorderedItems(this);
//Add item .. etc 
//return items

}

解决方法

只需将修改后的收藏AllItems保存在SharedPreferences中,并将其加载到应用程序开始&一旦您退出应用程序,就将其存储起来.

为此,您需要将您的集合序列化为json,并将其存储为String.然后反序列化：

public final class SharedPreferencesTools {
    private static final String USER_SETTINGS_PREFERENCES_NAME = "UserSettings";
    private static final String ALL_ITEMS_LIST = "AllItemsList";
    private static Gson gson = new GsonBuilder().create();

    public static List<Item> getorderedItems(Context context) {
        String stringValue = getUserSettings(context).getString(ALL_ITEMS_LIST,"");
        Type collectionType = new Typetoken<List<Item>>() {
        }.getType();
        List<Item> result = gson.fromJson(stringValue,collectionType);
        return (result == null) ? new ArrayList<Item>() : result;
    }

    public static void setorderedItems(Context context,List<Item> items) {
        String stringValue = gson.toJson(items);

        SharedPreferences sharedPreferences = getUserSettings(context);
        SharedPreferences.Editor editor = sharedPreferences.edit();
        editor.putString(ALL_ITEMS_LIST,stringValue);
        editor.apply();        
    }

    static SharedPreferences getUserSettings(Context context) {
        return context.getSharedPreferences(USER_SETTINGS_PREFERENCES_NAME,Context.MODE_PRIVATE);
    }
}

使用这两种方法：

SharedPreferencesTools.setorderedItems(getActivity(),AllItems);
 ...
 List<Item> AllItems = SharedPreferencesTools.getorderedItems(getActivity());