将ArrayList <Map <String,String >>保存到SQLite数据库？

Question

我有一个包含a 的Fragment被叫.其中的项目由另一个叫做的类添加.我想要做的是在项目添加到列表时保存列表.(目前,我的列表中的视图只是s,但后来我希望向它们添加图像,并且有多行等等,所以这些也需要保存).我的列表是:它被调用.HistoryFragmentListViewListViewDataModelTextViewArrayList<Map<String, String>>mPlanetList

我认为保存到a SQLiteDataBase是解决方案,但即使在阅读了多个答案/教程后看起来也很复杂.

我看过的一些网站:

http://www.vogella.com/articles/AndroidSQLite/
http://developer.android.com/guide/topics/data/data-storage.html#db
http://stackoverflow.com/q/5482402/2442638
http://stackoverflow.com/q/3142285/2442638

这个"问题"中有很多问题,但我的主要问题分为两部分:

a)是DataBase正确的解决方案吗？

- >如果'是' - > b)制作一个简单的方法是什么？我宁愿不使用JSON/GSON

- >如果'不' - > c)我应该使用什么？ SharedPreferences？

假设a DataBase是正确的解决方案,我想我需要序列化我的arraylist或者可能使用StringSet - 我不知道怎么做,因为我有这样的arraylist:ArrayList<Map<String, String>> 而不是没有map对象的arraylist.

此外,我试图从我的DataModel类访问我的数据库(因为这是我将我的项目添加到列表中),但我无法让它工作.

我已经添加了我当前的代码 - 数据库的工作还没有完成,但我仍然坚持下一步该做什么.

这是我的HistoryFragment班级:

// Remove imports

public class HistoryFragment extends FragmentBase implements OnItemAddedHandler {
// FragmentBase is just another class which extends Fragment and the moment.

    ListView lv;
    SimpleAdapter simpleAdpt;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        View view = inflater.inflate(R.layout.history, container, false);

        ListView lv = (ListView) view.findViewById(R.id.listView);


        List<Map<String, String>> planetsList = DataModel.getInstance()
                .getPlanetList();
        simpleAdpt = new SimpleAdapter(getActivity(), planetsList,
                android.R.layout.simple_list_item_1, new String[] { "planet" },
                new int[] { android.R.id.text1 });

        lv.setAdapter(simpleAdpt);
        lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {

            public void onItemClick(AdapterView<?> parentAdapter, View view,
                    int position, long id) {


                TextView clickedView = (TextView) view;

        // Display a dialog
            }
        });

        return view;
    }

    @Override
    public void onDetach() {
        super.onDetach();
        DataModel.getInstance().setOnItemAddedHandler(null);
    }

    @Override
    public void onItemAdded(Object data) {
        simpleAdpt.notifyDataSetChanged();
        lv.scrollTo(0, 0); // Scrolls to top of list
    }

    @Override
    public void onStart() {
        super.onStart();
        DataModel.getInstance().setOnItemAddedHandler(this);
    }

}

这是我的DataModel:

public class DataModel {

    private List<Map<String, String>> mPlanetsList = new ArrayList<Map<String, String>>();

    private static DataModel instance;
    private static OnItemAddedHandler mOnItemAddHandler;

    private DataModel() {
        initList();
    }

    public static DataModel getInstance() {
        if (null == instance) {
            instance = new DataModel();
        }
        return instance;
    }

    private void initList() { 
// Here is where I want to load the saved listitems.
    }

    public List<Map<String, String>> getPlanetList() {
        return mPlanetsList;
    }

    private HashMap<String, String> createPlanet(String key, String name) {

        HashMap<String, String> planet = new HashMap<String, String>();
        planet.put(key, name);
        return planet;
    }

    public void setOnItemAddedHandler(OnItemAddedHandler handler) {
        mOnItemAddHandler = handler;
    }

    public void addItem(Object data) { // Save stuff here?
        Bundle data1 = new Bundle();
        String string = ((Bundle) data).getString("keyTitle");
        mPlanetsList.add(0, createPlanet("planet", string)); 

 // This is where I want to save my items to the DataBase
    HistoryDataBase.getInstance();  //Adding .getWritableDatabase()  gives me a nullpointerexception.

// I don't understand what else I need to do here to add my mPlanetList to the DataBase

        if (null != mOnItemAddHandler) {
            mOnItemAddHandler.onItemAdded(data1);
        }
    }
}

最后这是我的数据库:

public class HistoryDataBase extends SQLiteOpenHelper {

private static HistoryDataBase instance;

public static final String TABLE_COMMENTS = "comments";
  public static final String COLUMN_ID = "_id";
  public static final String COLUMN_COMMENT = "comment";

  private static final String DATABASE_NAME = "commments.db";
  private static final int DATABASE_VERSION = 1;

  // Database creation sql statement
  private static final String DATABASE_CREATE = "create table "
      + TABLE_COMMENTS + "(" + COLUMN_ID
      + " KEY, " + COLUMN_COMMENT
      + " text not null);";

static Context c;

HistoryDataBase(Context context) {
    super(c, DATABASE_NAME, null, DATABASE_VERSION);
}

@Override
public void onCreate(SQLiteDatabase db) {
    db.execSQL(DATABASE_CREATE);

}

@Override
public void onUpgrade(SQLiteDatabase arg0, int arg1, int arg2) {
    // TODO Auto-generated method stub

}

public static HistoryDataBase getInstance() {
    if (null == instance) {

        instance = new HistoryDataBase(c);
    }
    return instance;
}
}

非常基本:我想永久保存我的列表项,并能够进行检索,编辑和删除它们.

感谢您抽出时间来阅读.如果需要澄清,请说.

Answer 1

这SQLiteDataBase是正确的解决方案.

您可以将每个项目的数据保存到数据库中.如果要将整数或其他简单类型数据放入hashmap,将会有一个HashMap<String, Object>而不是HashMap<String, String>每个项目数据.

然后,您可以序列化HashMap到json时你要保存到数据库:

    // you can put multiple data into this hashmap
    HashMap<String, Object> dataHashMap = new HashMap<String, Object>();

    ContentValues values = new ContentValues();
    values.put("data", new JSONObject(dataHashMap).toString());
    db.insert(TABLE_NAME, COL_ID, values);

unserialize从数据库中获取序列化数据后可以执行以下操作:

    int rawDataIndex = 6;
    String rawData = cursor.getString(rawDataIndex);
    HashMap<String, Object> dataHashMap = new HashMap<String, Object>();

    try {
        JSONObject json = new JSONObject(rawData);
        JSONArray names = json.names();
        for (int i = 0; i < names.length(); i++) {
            String key = names.getString(i);
            dataHashMap.put(key, json.opt(key));
        }
    } catch (JSONException e) {
        e.printStackTrace();
    }