在Android中使用外部数据库文件

Question

I am using DB browser for SQLite to create an external database, the file name's words_library.db inside that file I have a table called dictionary.db that contains 3 columns : "English_lib", "German_lib", "_id" as shown below (Fig. 1)

What I am trying to do is populating a recyclerview with that database but I failed to do so.

JAVA

public void fetchData() //this method is called to populate the RecyclerView
{
    db =new DataBaseHelper(getContext());
    try {

        db.createDataBase();
        db.openDataBase();

    }
    catch (Exception e)
    {
        e.printStackTrace();
    }

    namelist=new LinkedHashMap<>();
    int ii;
    SQLiteDatabase sd = db.getReadableDatabase();
    Cursor cursor = sd.query("dictionary_lib" ,null, null, null, null, null, null);
    ii=cursor.getColumnIndex("_id");
    eng_list=new ArrayList<String>();
    ger_list= new ArrayList<String>();
    id_list= new ArrayList<String>();
    cursor.moveToFirst();
    while (cursor.moveToNext()){
        namelist.put(cursor.getString(ii), cursor.getString(cursor.getColumnIndex("English_lib")));
    }

    Iterator entries = namelist.entrySet().iterator();
    while (entries.hasNext()) {
        Map.Entry thisEntry = (Map.Entry) entries.next();
        id_list.add(String.valueOf(thisEntry.getKey()));
        eng_list.add(String.valueOf(thisEntry.getValue()));
        ger_list.add(String.valueOf(thisEntry.getValue()));
    }

    for (int i = 0; i < eng_list.size(); i++) {
        data.add(new DictObjectModel(eng_list.get(i), ger_list.get(i)));
    }
    adapter = new CustomAdapter(data);
    rv.setAdapter(adapter);
}

LOG

Failed to read row 1, column -1 from a CursorWindow which has 3469 rows, 2 columns.
java.lang.IllegalStateException: Couldn't read row 1, col -1 from CursorWindow.  
Make sure the Cursor is initialized correctly before accessing data from it.

fig 1 :

an example of the database I have and the recyclerview should only have the English_lib and the German_lib columns shown

Answer 1

to do so :

1- change the PK column name to "rowid" instead of "_id" (this will fix a lot of PK related problems not only this one)

2- update the code by adding new variables and lists like so:

public void fetchData()
{
    db = new DataBaseHelper(getContext());
    try {

        db.createDataBase();
        db.openDataBase();

    }
    catch (Exception e)
    {
        e.printStackTrace();
    }

    namelist = new LinkedHashMap<>();
    nmlist = new LinkedHashMap<>();
    int ii;
    SQLiteDatabase sd = db.getReadableDatabase();
    Cursor cursor = sd.query("dictionary_lib" ,new String[]{
            "English_lib", "German_lib", "rowid"
    }, null, null, null, null, null);
    ii=cursor.getColumnIndexOrThrow("rowid");
    eng_list = new ArrayList<String>();
    ger_list = new ArrayList<String>();
    id_list = new ArrayList<String>();
    while (cursor.moveToNext()){
        namelist.put(cursor.getString(ii), cursor.getString(cursor.getColumnIndexOrThrow("English_lib")));
        nmlist.put(cursor.getString(ii), cursor.getString(cursor.getColumnIndexOrThrow("German_lib")));
    }

    Iterator entries = namelist.entrySet().iterator();
    Iterator entrs = nmlist.entrySet().iterator();
    while (entries.hasNext() && entrs.hasNext()) {
        Map.Entry thisEntry = (Map.Entry) entries.next();
        Map.Entry altEntry = (Map.Entry) entrs.next();
        id_list.add(String.valueOf(thisEntry.getKey()));
        eng_list.add(String.valueOf(thisEntry.getValue()));
        ger_list.add(String.valueOf(altEntry.getValue()));
    }

    for (int i = 0; i < id_list.size(); i++) {
        data.add(new DictObjectModel(eng_list.get(i), ger_list.get(i)));
    }
    adapter = new CustomAdapter(data);
    rv.setAdapter(adapter);
}