Question

我有一个数据库.sqlite，我想在我的Android应用程序上使用它并获取它的一些数据。我看到了这个教程：http://www.reigndesign.com/blog/using-your-own-sqlite-database-in-android-applications/但是现在我想将一些数据保存在String []中，然后将它放在listview上，但我不知道如何检索数据库的数据。我在\ myproject \ app \ src \ main \ assets中有 comidas.sqlite （我创建了资产文件夹，其中包含＆＃34; java＆＃34;以及＆＃34; res＆＃34;文件夹，但我不知道是否是正确的文件夹）我有 DBAlimentos.java 类，我连接到数据库（我使用顶部链接的代码）但现在我不知道如何在我的活动中检索数据。我要保存的数据是返回此行的所有记录：＆＃34; SELECT nombre FROM comida WHERE imagen_id =＆＃39; 1＆＃39; ＆＃34;

我的DBAlimentos.java代码：

public class DBAlimentos extends SQLiteOpenHelper {

    //The Android's default system path of your application database.
    private static String DB_PATH = "/data/data/es.bawi.testdeporte/databases/";

    private static String DB_NAME = "comidas.sqlite";

    public static SQLiteDatabase myDataBase;

    private final Context myContext;

    /**
     * Constructor
     * Takes and keeps a reference of the passed context in order to access to the application assets and resources.
     * @param context
     */
    public DBAlimentos(Context context) {

        super(context, DB_NAME, null, 1);
        this.myContext = context;
    }

    /**
     * Creates a empty database on the system and rewrites it with your own database.
     * */
    public void createDataBase() throws IOException {

        boolean dbExist = checkDataBase();

        if(dbExist){
            //do nothing - database already exist
        }else{

            //By calling this method and empty database will be created into the default system path
            //of your application so we are gonna be able to overwrite that database with our database.
            this.getReadableDatabase();

            try {

                copyDataBase();

            } catch (IOException e) {

                throw new Error("Error copying database");

            }
        }

    }

    /**
     * Check if the database already exist to avoid re-copying the file each time you open the application.
     * @return true if it exists, false if it doesn't
     */
    private boolean checkDataBase(){

        SQLiteDatabase checkDB = null;

        try{
            String myPath = DB_PATH + DB_NAME;
            checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);

        }catch(SQLiteException e){

            //database does't exist yet.

        }

        if(checkDB != null){

            checkDB.close();

        }

        return checkDB != null ? true : false;
    }

    /**
     * Copies your database from your local assets-folder to the just created empty database in the
     * system folder, from where it can be accessed and handled.
     * This is done by transfering bytestream.
     * */
    private void copyDataBase() throws IOException{

        //Open your local db as the input stream
        InputStream myInput = myContext.getAssets().open(DB_NAME);

        // Path to the just created empty db
        String outFileName = DB_PATH + DB_NAME;

        //Open the empty db as the output stream
        OutputStream myOutput = new FileOutputStream(outFileName);

        //transfer bytes from the inputfile to the outputfile
        byte[] buffer = new byte[1024];
        int length;
        while ((length = myInput.read(buffer))>0){
            myOutput.write(buffer, 0, length);
        }

        //Close the streams
        myOutput.flush();
        myOutput.close();
        myInput.close();

    }

    public static void openDataBase() throws SQLException {

        //Open the database
        String myPath = DB_PATH + DB_NAME;
        myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);

    }

    @Override
    public synchronized void close() {

        if(myDataBase != null)
            myDataBase.close();

        super.close();

    }

    @Override
    public void onCreate(SQLiteDatabase db) {

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

    }

    // Add your public helper methods to access and get content from the database.
    // You could return cursors by doing "return myDataBase.query(....)" so it'd be easy
    // to you to create adapters for your views.

}

谢谢，抱歉我的英语不好......

Answer 1

如果您真的想使用原始SQL查询它或使用首选（更安全）myDataBase.rawQuery("SELECT ...")接口，您可以使用query：

mDataBase.query("comida", {"nombre"}, "imagen_id=?", {"1"}, null, null, null);

Answer 2

你必须得到一个新的游标，用你的语句查询数据库，对吧？

所以你想要做的是，我想，

public List<String> getNames(){
String TABLE_NAME = "comida"
String TABLE_ID = "imagen_id";
String WhereClause = TABLE_ID+"=?";
String Args = "1";
String TABLE_ROW_ONE = "nombre";
List<String> names = new ArrayList<String>();

//EDIT FOR CLARIFICATION
myDataBase = DBAlimentos.getWritableDatabase();

Cursor _cursor = myDataBase.query(TABLE_NAME, TABLE_ROW_ONE, WhereClause, Args, null, null, null);

    if(_cursor.getCount() > 0){
       if (_cursor.moveToFirst()){
        do{

           names.add( _cursor.getString(TABLE_ROW_ONE))); 
        }while(_cursor.moveToNext())
    }
    _cursor.close();
    return names;
    }
}

如何从我自己的数据库中获取值

2 个答案: