Question

我使用此类将我的数据库从assets文件夹复制到app文件夹（data / data / pckname / database）。但它只创建一个数据库，不会将表和内容复制到它。当我运行应用程序时出错：＆＃34; android.database.sqlite.SQLiteException：没有这样的表...＆＃34;

public class DB3 extends SQLiteOpenHelper{

//The Android's default system path of your application database.
private static String DB_PATH = "/data/data/ir.ratinapps.idioms/databases/";

private static String DB_NAME = "101.sqlite";

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 DB3(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 SQLiteDatabase openDataBase() throws SQLException{

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

@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.
}

Answer 1

也许我的回答并没有多大帮助，但几个月前我遇到了同样的问题，我一直在寻找信息，最后得出的结论是更好地使用一些ORM。我开始使用greenDAO。也许对你来说和我一样有用。

http://greendao-orm.com/

从资产中复制android数据库

1 个答案: