Question

我尝试将已存在的数据库从我的资产文件夹（Cultureheleper / mobile / src / main / assets / databases）复制到系统中，以便在我的代码中使用它。这是我的DBHellper：

/* 
========== VENDOR
*/
@import "compass/utilities/sprites";
@import "compass/css3/images";
@import "compass/css3/border-radius";
@import "compass/css3/box-shadow"; 

/* 
========== UTILS 
*/
@import "utils/variables.cp.scss";

/* 
========== COMPONENTS 
*/
@import "components/CP/container";

这就是我在MainCtivity的onCreate（）中调用它的方式：

Error: Undefined mixin 'background-image'.
        on line 165 of D:/TestRepo/mobile.application/trunk/scss/utils/_variables.cp.scss, in `background-image'
        from line 165 of D:/TestRepo/mobile.application/trunk/scss/utils/_variables.cp.scss, in `cpButton-silver'
        from line 246 of D:/TestRepo/mobile.application/trunk/scss/components/CP/_overwrite.scss
        from line 20 of D:\TestRepo\mobile.application\trunk\scss\mobile_CP.scss
  Use --trace for backtrace.

首次安装时出现此错误：

public class DatabaseCall extends SQLiteOpenHelper {


private final static int DB_Version =1;

private static String DB_PATH =  "/data/data/de.gruppe8.culturehelper/databases/";
private final static String DB_Name = "DB.db";
private SQLiteDatabase myDataBase;
private final Context myContext;

/*  private final static String tabelle1 = "Nutzer";

private final static String nutzer_id = "nutzer_id";
private final static String nutzer_name = "nutzer_Name";
private final static String nutzer_email = "nutzer_email";*/

public DatabaseCall(Context context){
    super(context,DB_Name,null,DB_Version );
    Log.i("DB", "anfang gemacht");
    this.myContext = context;
}

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();
            copyDataBase();
    }

}

/**
 * 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;

        //myDataBase.close();

    //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) {

}
public void Anfrage(String Anfrage){
  /*  String myPath = DB_PATH + DB_Name;
    myDataBase = SQLiteDatabase.openDatabase(myPath, null,  SQLiteDatabase.OPEN_READONLY);*/
    Log.i("DB","bis hierhin hat alles funktioniert");
    myDataBase.execSQL(Anfrage);

}

}

On Secondd open我得到以下错误：

    try {
        DB.createDataBase();

    } catch (IOException ioe) {
        throw new Error("Unable to create database");
    }
    try {

        DB.openDataBase();

    }catch(SQLException sqle){
        throw sqle;
    }

      DB.Anfrage("SELECT * FROM Ort;");

Answer 1

使用SQLiteDatabase#query或SQLiteDatabase#rawQuery，因为SQLiteDatabase#execSQL适用于：

执行一个非SELECT或任何其他SQL的SQL语句返回数据的语句

无法复制现有数据库

1 个答案: