java - How do I implement autocomplete with cursoradapter

Question

I have an SQLite database containing 2 tables 4000+ rows each used for autocomplete. I saw very simple examples that use an array of strings to provide autocomplete or they use the list of contacts to do the same. Obviously none of these work in my case. How do I use my own SQLite database with my own autocomplete data, for the autocomplete. Do I have to create content providers? How? Please give me some examples because I couldn't find any. I have managed to override SQLiteOpenHelper to copy the database from the assets folder to the /data/data/MY_PACKAGE/databases/ folder on the android. I have created a custom CursorAdapter that uses my custom SQLiteOpenHelper and returns a cursor from runQueryOnBackgroundThread. I get strange errors about some _id column missing. I have added the _id column to my tables. I also don't understand what is the Filterable interface doing and when does my data get filtered. What methods/classes do I need to override? Thanks.

Answer 1

有用。

您需要这里的 SQLiteOpenHelper 。您基本上必须将数据库从资产文件夹复制到特定文件夹中。然后，您需要一个使用自定义 SQLiteOpenHelper 的自定义 CursorAdapter。

这是我的活动的 onCreate 方法。

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.search);

        KeywordsCursorAdapter kwadapter = new KeywordsCursorAdapter(this, null);

        txtKeyword = (AutoCompleteTextView)this.findViewById(R.id.txtKeyword);
        txtKeyword.setAdapter(kwadapter);
        txtCity = (AutoCompleteTextView)this.findViewById(R.id.txtCity);
        btnSearch = (Button)this.findViewById(R.id.btnSearch);
        btnSearch.setOnClickListener(this);
    }

这是光标适配器。您可以在构造时为游标传递 null。

public class KeywordsCursorAdapter extends CursorAdapter {

    private Context context;

    public KeywordsCursorAdapter(Context context, Cursor c) {
        super(context, c);
        this.context = context;
    }

    //I store the autocomplete text view in a layout xml.
    @Override
    public View newView(Context context, Cursor cursor, ViewGroup parent) {
        LayoutInflater inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        View v = inflater.inflate(R.layout.keyword_autocomplete, null);
        return v;
    }

    @Override
    public void bindView(View view, Context context, Cursor cursor) {
        String keyword = cursor.getString(cursor.getColumnIndex("keyword"));
        TextView tv = (TextView)view.findViewById(R.id.txtAutocomplete);
        tv.setText(keyword);
    }

    //you need to override this to return the string value when
    //selecting an item from the autocomplete suggestions
    //just do cursor.getstring(whatevercolumn);
    @Override
    public CharSequence convertToString(Cursor cursor) {
        //return super.convertToString(cursor);
        String value = "";
        switch (type) {
        case Keywords:
            value = cursor.getString(DatabaseHelper.KEYWORD_COLUMN);
            break;
        case Cities:
            value = cursor.getString(DatabaseHelper.CITY_COLUMN);
            break;
        }
        return value;
    }

    @Override
    public Cursor runQueryOnBackgroundThread(CharSequence constraint) {
        //return super.runQueryOnBackgroundThread(constraint);
        String filter = "";
        if (constraint == null) filter = "";
        else
            filter = constraint.toString();
                //I have 2 DB-s and the one I use depends on user preference
        SharedPreferences prefs  = PreferenceManager.getDefaultSharedPreferences(context);
        //String selectedCountryCode = prefs.getString("selectedCountry", "GB");
        String selectedCountryCode = prefs.getString(context.getString(R.string.settings_selected_country), "GB");
        selectedCountryCode += "";

                //Here i have a static SQLiteOpenHelper instance that returns a cursor.
        Cursor cursor = MyApplication.getDbHelpers().get(selectedCountryCode.toLowerCase()).getKeywordsCursor(filter);
        return cursor;
    }
}

这是返回光标的部分：它只是一个具有类似条件的选择。

public class DatabaseHelper extends SQLiteOpenHelper {

...

    public synchronized Cursor getKeywordsCursor (String prefix) {
        if (database == null) database = this.getReadableDatabase();
        String[] columns = {"_id", "keyword"};
        String[] args = {prefix};

        Cursor cursor;
        cursor = database.query("keywords", columns, "keyword like '' || ? || '%'", args, null, null, "keyword", "40");

        int idcol = cursor.getColumnIndexOrThrow("_id");
        int kwcol = cursor.getColumnIndexOrThrow("keyword");

        while(cursor.moveToNext()) {
            int id = cursor.getInt(idcol);
            String kw = cursor.getString(kwcol);
            Log.i("keyword", kw);
        }

        cursor.moveToPosition(-1);
        return cursor;
    }

...

}

您还可以创建自定义内容提供程序，但在这种情况下，它只是您需要覆盖的另一个无用类。