1
public class DBHelper extends SQLiteOpenHelper{

    //The Android's default system path of your application database.
    private static String DB_PATH = "/data/data/com.tmm.android.chuck/databases/";
    private static String DB_NAME = "questionsDb";
    private 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 DBHelper(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)
        {
            //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 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.




    public List<Question> getQuestionSet(int difficulty, int numQ){
        List<Question> questionSet = new ArrayList<Question>();
        Cursor c = myDataBase.rawQuery("SELECT * FROM QUESTIONS WHERE DIFFICULTY=" + difficulty +
                " ORDER BY RANDOM() LIMIT " + numQ, null);
        while (c.moveToNext()){
            //Log.d("QUESTION", "Question Found in DB: " + c.getString(1));
            Question q = new Question();
            q.setQuestion(c.getString(1));
            q.setAnswer(c.getString(2));
            q.setOption1(c.getString(3));
            q.setOption2(c.getString(4));
            q.setOption3(c.getString(5));
            q.setRating(difficulty);
            questionSet.add(q);
        }
        return questionSet;
    }
}

LogCat 错误信息:

android.database.sqlite.SQLiteException: no such table: question (code 1): , while compiling: SELECT * FROM question WHERE DIFFICULTY=2 ORDER BY RANDOM() LIMIT 20

我在资产文件夹中添加了数据库。它有表 " question" 和列_id," question"、" answer"、" option1"、" option2"、" option3"、" difficulty"。

4

2 回答 2

1

试试这门课。您只需要确保旧数据库当前不在您的设备中,因为您可以重新安装应用程序。

public class DatabaseHepler extends SQLiteOpenHelper{

public DatabaseHepler(Context context)
    {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
        this.myContext = context;   
        try
        {   
            createDataBase();
            //BugSenseHandler.setup(this.myContext, "0670ce92");
            //BugSenseHandler.readLogs(); 
        }
        catch (Exception e)
        {   
            Log.e(TAG,"DatabaseHelper_constuctor createDataBase :" + e.fillInStackTrace());   
        }
    }


    private static final String TAG = "DatabaseHelper"; 
    //Your Database Name
    private static final String DATABASE_NAME = "questionDb.sqlite";
    //Your Your Database Version
    private static final int DATABASE_VERSION = 1;
    private final Context myContext;
    private static SQLiteDatabase myDataBase; 
    //The Android's default system path of your application database. DB_PATH = "/data/data/YOUR_PACKAGE/databases/"
    private static String DB_PATH = "/data/data/com.tmm.android.chuck/databases/";

//*****************************  Constructor *****************************
/**
* Constructor
* Takes and keeps a reference of the passed context in order to access to the application assets and resources.
* @param context
**/

//*****************************  SQLiteOpenHelper's Methods *****************************
@Override
public void onCreate(SQLiteDatabase db) {
}

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


@Override
public synchronized void close() 
{
        if(myDataBase != null)
            myDataBase.close();
        super.close();
}

//*****************************  My DB Handler Methods *****************************
/**
* Creates a empty database on the system and rewrites it with your own database.
**/
public void createDataBase() throws IOException
{
    boolean dbExist = checkDataBase();
    if(dbExist)
    {
        //Database already exist
        openDataBase();
        
    }
    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.
        myDataBase = getWritableDatabase();
        try 
        {
            copyDataBase(); 
        } 
        catch (IOException e) 
        {
            throw new Error("Error createDataBase().");
        }
    }
}
/**
* 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 + DATABASE_NAME;
        checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);
    }
    catch(SQLiteException e)
    {
        //database does't exist yet.
    }
    if(checkDB != null)
    {
        checkDB.close();
    }
    return checkDB != null ? true : false;
}
/*public boolean isDataBaseExist() 
{
    File dbFile = new File(DB_PATH + DATABASE_NAME);
    return dbFile.exists();
}*/

/**
* 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 transferring bytestream.
**/ 
private void copyDataBase() throws IOException
{
    try
    {
        //Open your local db as the input stream
        InputStream myInput = myContext.getAssets().open("DATABASE_NAME");
        
        // Path to the just created empty db
        String outFileName = DB_PATH + DATABASE_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();
    }
    catch (IOException e) 
    {
        throw new Error("Error copyDataBase().");
    }
}

public void openDataBase() throws SQLException, IOException
{
    try 
    {
        //Open the database
        String myPath = DB_PATH + DATABASE_NAME;
        myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);
    } 
    catch (SQLiteException e) 
    {
        throw new Error("Error openDataBase().");
    }       
}

public static List<ItemClass> getAnswerList()
{
    List<ItemClass> resultList = new ArrayList<ReminderItemClass>();
    ItemClass obj;
    Cursor cursor;
    String query;
    
    query = "SELECT * FROM tblName"; 
    try
    {
        cursor = myDataBase.rawQuery(query,null); 
        if(cursor != null)
        {
            
            while(cursor.moveToNext())
            {
                obj=new ReminderItemClass();
                obj.id=cursor.getString(0);
                obj.title=cursor.getString(1);
                .
            .
                resultList.add(obj);
            }
        }
        cursor.deactivate();
        
        
    }
    catch (Exception e)
    {
        Log.e(TAG,"Error : " + e.fillInStackTrace());
        
    }
    return resultList;
}


}

您没有通过编码完全复制数据库。

于 2013-05-14T05:35:08.120 回答
0

您的代码在行中引用了表“QUESTIONS”而不是“question”

Cursor c = myDataBase.rawQuery("SELECT * FROM QUESTIONS WHERE DIFFICULTY=" + difficulty +
" ORDER BY RANDOM() LIMIT " + numQ, null);
于 2013-05-14T05:19:46.880 回答