使用android中的现有数据库

我已经为使用android中的现有数据库编写了这段代码

我拥有的是：

• 数据库：测试
• 表：t1

我已将数据库保存在

资产

文件夹中，如果我运行项目，它会给我

强制关闭

错误

我哪里做错了

public class BDAdapter extends SQLiteOpenHelper {
     private Context mycontext;
int id=0;
        private String DB_PATH = "data/data/com.example.dd9/databases/";
        private static String DB_NAME = "test.sqlite";
     //   public static final String KEY_ROWID = "_id";
        public static final String KEY_QUOTE = "name";
        private static final String DATABASE_TABLE = "t1";
        private static final String TAG = "BDAdapter";
        private static final String DATABASE_CREATE =
                "create table t1 ( "
                + "name text not null );";

        private SQLiteDatabase db;



        public BDAdapter(Context context) {
            super(context, DB_NAME, null, 1);
            this.mycontext = context;
            boolean dbexist = checkdatabase();
            if (dbexist) {
            } else {
                System.out.println("Database doesn't exist");
                try {
                    createdatabase();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }

        }

        public void createdatabase() throws IOException {
            boolean dbexist = checkdatabase();
            if (dbexist) {
            } else {
                this.getReadableDatabase();
                try {
                    copydatabase();
                } catch (IOException e) {
                    throw new Error("Error copying database");
                }
            }
        }

        private boolean checkdatabase() {
            boolean checkdb = false;
            try {
                String myPath = DB_PATH + DB_NAME;
                File dbfile = new File(myPath);
                checkdb = dbfile.exists();
            } catch (SQLiteException e) {
                System.out.println("Database doesn't exist");
            }

            return checkdb;
        }

        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
            @SuppressWarnings("unused")
            String outfilename = DB_PATH + DB_NAME;

            // Open the empty db as the output stream
            OutputStream myoutput = new FileOutputStream(
                    "data/data/com.example.dd9/databases/test.sqlite");

            // transfer byte to inputfile to 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 open() {
            // Open the database
            String mypath = DB_PATH + DB_NAME;
            myDataBase = SQLiteDatabase.openDatabase(mypath, null,
                    SQLiteDatabase.OPEN_READWRITE);

        }

        public synchronized void close() {
            myDataBase.close();
            super.close();
        }

        @Override
        public void onCreate(SQLiteDatabase db) {
            // TODO Auto-generated method stub
            db.execSQL(DATABASE_CREATE);

        }

        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
            // TODO Auto-generated method stub
            Log.w(TAG, "Upgrading database from version " + oldVersion + " to "
                    + newVersion + ", which will destroy all old data");
            db.execSQL("DROP TABLE IF EXISTS t1");
            onCreate(db);


        }

        public long insertQuote(String Quote) 
        {
            ContentValues initialValues = new ContentValues();
            initialValues.put(KEY_QUOTE, Quote);
            return db.insert(DATABASE_TABLE, null, initialValues);
        }

        public int getAllEntries() 
        {
            Cursor cursor = db.rawQuery(
                        "SELECT COUNT(name) FROM t1", null);
                    if(cursor.moveToFirst()) {
                        return cursor.getInt(0);
                    }
                    return cursor.getInt(0);

        }

        public String getRandomEntry() 
        {

            id = getAllEntries();
            Random random = new Random();
            int rand = random.nextInt(getAllEntries());
            if(rand == 0)
                ++rand;
            Cursor cursor = db.rawQuery(
                      "SELECT name FROM t1 ", null);
                    //"SELECT * FROM tblRandomQuotes",null);
                    if(cursor.moveToFirst()) {
                        return cursor.getString(0);

                    }
                    return cursor.getString(0);

        }

        public Cursor getAllTitles() 
        {
            return db.query(DATABASE_TABLE, new String[] {

                    KEY_QUOTE,
                    }, 
                    null, 
                    null, 
                    null, 
                    null, 
                    null);
        }


}



//---------------------------Main class------------------------

public class MainActivity extends Activity
{
    BDAdapter db = new BDAdapter(this);
    EditText name;
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        // Capture our button from layout
        Button setButton = (Button)findViewById(R.id.go);
        Button getButton = (Button)findViewById(R.id.genRan);
        // Register the onClick listener with the implementation above
        setButton.setOnClickListener(mAddListener);
        getButton.setOnClickListener(mAddListener);
    }

    // Create an anonymous implementation of OnClickListener
    private OnClickListener mAddListener = new OnClickListener() 
    {
        public void onClick(View v) 
        {
            switch(v.getId())
            {
            case R.id.go:
                db.open();
                long id = 0;
                // do something when the button is clicked
                try
                {
                    name = (EditText)findViewById(R.id.Quote);
                    db.insertQuote(name.getText().toString());


                    id = db.getAllEntries();

                    Context context = getApplicationContext();
                    CharSequence text = "The quote '" + name.getText() + "' was added successfully!\nQuotes Total = " + id;
                    int duration = Toast.LENGTH_LONG;

                    Toast toast = Toast.makeText(context, text, duration);
                    toast.show();
                    name.setText("");
                }
                catch (Exception ex)
                {
                    Context context = getApplicationContext();
                    CharSequence text = ex.toString() + "ID = " + id;
                    int duration = Toast.LENGTH_LONG;

                    Toast toast = Toast.makeText(context, text, duration);
                    toast.show();
                }

                db.close();
                break;
            case R.id.genRan:
                db.open();
                //long id1 = 0;
                // do something when the button is clicked
                try
                {
                    //String quote = "";
                    //quote = db.getRandomEntry();
                    //Context context = getApplicationContext();
                    //CharSequence text = quote;
                    //int duration = Toast.LENGTH_LONG;

                    //Toast toast = Toast.makeText(context, text, duration);
                    //toast.show();

                     db.open();
                        Cursor c = db.getAllTitles();
                       if (c.moveToFirst())
                       {
                          do {          
                                DisplayTitle(c);
                            } while (c.moveToNext());
                       }
                        db.close();


                }
                catch (Exception ex)
                {
                    Context context = getApplicationContext();
                    CharSequence text = ex.toString();
                    int duration = Toast.LENGTH_LONG;

                    Toast toast = Toast.makeText(context, text, duration);
                    toast.show();
                }
                db.close();
            }
        }

    };
    public void DisplayTitle(Cursor c)
    {
        Toast.makeText(this, 
                "NAME: " + c.getString(0) + "\n" ,


                Toast.LENGTH_LONG).show();        
    } 


}

试试这个：

public class DBHelper extends SQLiteOpenHelper {

private static String TAG = "DBHelper";
private static boolean DEBUG = true;

private static String PKG;
private static final String DB_NAME="C&EN.sqlite";
private Context mContext;

private static DBHelper instance;

public static DBHelper getInstance(Context ctx){
    if(instance == null || !ctx.equals(instance.mContext)){
        instance = new DBHelper(ctx);
    }
    return instance;

}

private DBHelper(Context context) {

    super(context, DB_NAME, null,2);

    mContext = context;

    PKG= context.getPackageName();
    InputStream iStream;
    FileOutputStream fos;
    File file=new File("/data/data/"+PKG+"/databases/"+DB_NAME);
    if(!file.exists()){
        if(DEBUG)Log.i(TAG, "COPYING DATABASE TO PRIVATE FOLDER");
        try {
            iStream=context.getAssets().open(DB_NAME);
            new File("/data/data/"+PKG+"/databases").mkdirs();
            fos=new FileOutputStream(file);

            byte[] bte =new byte[1024];
            while(iStream.read(bte)!=-1){
                fos.write(bte);
            }
            iStream.close();
            fos.close();
        } catch (IOException e) {
            if(DEBUG)Log.i(TAG, "ERROR COPYING THE DATABASE");

        }
        if(DEBUG)Log.i(TAG, "DATABASE SUCCESSFULLY COPIED TO PRIVATE FOLDER");
    }

}

@Override
public void onCreate(SQLiteDatabase db) {

}

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

    }

}

---

}

u没有提到要复制的资产文件夹数据库路径我如何提到要复制的资产文件夹数据库路径？DB\u NAME是资产中的数据库文件名。：在调试中，在dp.open（）行显示此错误：找不到源！我该怎么办？