Question

我在资源文件夹中有SQLite数据库。我想使用此数据库来读取（选择）和编写（更新）目的。我能够读取记录但无法更新记录。

我使用以下代码访问数据库。

DBHelper类（以读/写模式创建数据库）
TestAdapter类
活动类（执行数据库操作）

DBHelper类代码：

public class DBHelper extends SQLiteOpenHelper {


    private static String TAG = "DataBaseHelper"; // Tag just for the LogCat window
    //destination path (location) of our database on device
    private static String DB_PATH = ""; 
    private static String DB_NAME ="";// Database name
    private SQLiteDatabase mDataBase; 
    private final Context mContext;

    public DBHelper(Context context,String DB_NAME) 
    {
        super(context, DB_NAME, null, 1);// 1? its Database Version
        this.DB_NAME=DB_NAME;
      //  DB_PATH = "/data/data/" + context.getPackageName() + "/databases/";

        this.mContext = context;
        DB_PATH =  mContext.getDatabasePath(DB_NAME).getPath();
    }   
public void createDataBase() throws IOException
{
    //If database not exists copy it from the assets

    boolean mDataBaseExist = checkDataBase();
    if(!mDataBaseExist)
    {
        this.getWritableDatabase();
       // this.close();
        try 
        {
            //Copy the database from assests
            copyDataBase();
            Log.e(TAG, "createDatabase database created");
        } 
        catch (IOException mIOException) 
        {
            throw new Error("ErrorCopyingDataBase");
        }
    }
}
    //Check that the database exists here: /data/data/your package/databases/Db Name
    private boolean checkDataBase()
    {
        File dbFile = new File(DB_PATH + DB_NAME);
        //Log.v("dbFile", dbFile + "   "+ dbFile.exists());
        return dbFile.exists();
    }

    //Copy the database from assets
    private void copyDataBase() throws IOException
    {
        InputStream mInput = mContext.getAssets().open(DB_NAME);
        String outFileName = DB_PATH + DB_NAME;
        //OutputStream mOutput = new FileOutputStream(outFileName);
        OutputStream mOutput = new FileOutputStream(DB_PATH);
        byte[] mBuffer = new byte[1024];
        int mLength;
        while ((mLength = mInput.read(mBuffer))>0)
        {
            mOutput.write(mBuffer, 0, mLength);
        }
        mOutput.flush();
        mOutput.close();
        mInput.close();
    }
     public SQLiteDatabase openDataBase() throws SQLException{
        //String myPath = DB_PATH + DB_NAME;
        String myPath = getWritableDatabase().getPath();
       mDataBase = SQLiteDatabase.openDatabase(myPath, null,SQLiteDatabase.OPEN_READWRITE);  
        return mDataBase;
    }
}

2。 TestAdapter类代码

public class TestAdapter {

    protected static final String TAG = "DataAdapter";

    private final Context mContext;
    private SQLiteDatabase mDb;
    private com.gre.db.DBHelper mDbHelper;
    public TestAdapter(Context context,String DB_NAME) 
    {
        this.mContext = context;
        mDbHelper = new com.gre.db.DBHelper(mContext,DB_NAME);
    }
    public SQLiteDatabase open() throws SQLException 
    {
        try 
        {
           mDb = mDbHelper.openDataBase();

          //  mDb = mDbHelper.getWritableDatabase();
        } 
        catch (SQLException mSQLException) 
        {
            Log.e(TAG, "open >>"+ mSQLException.toString());
            throw mSQLException;
        }
        return mDb;
    }
}

第3。用于执行数据库操作的活动类

     TestAdapter adapter = new TestAdapter(this, "GREDB");
     SQLiteDatabase  db = adapter.open();
     String whereClause = where_clause="WORDID like '"+compare_wordid+"'";              
     ContentValues cv= new ContentValues();
     cv.put("RATING",ref_rate);
     int n=db.update("WORD_A", cv, where_clause, null);
     Toast.makeText(getApplicationContext(), "Rating updated to "+ref_rate,
     Toast.LENGTH_LONG).show();

提供评分更新的吐司信息。但它没有在数据库中更新。

任何人都可以帮助我。非常感谢您的帮助......

谢谢....

无法执行从Assets文件夹更新SQLite数据库中的记录

0 个答案: