Question

我是Android开发的新手，所以我有一个名为Courses的现有数据库和DatabaseHelper文件，它将从Android工作室的assets文件夹中复制现有文件，但它运行循环并创建一个带有android_manifest文件的空数据库，＆＃34;没有表格被复制＆＃34;。因此，给我和运行选择表时找不到表格的错误。

错误： E / AndroidRuntime：致命异常：主要进程：com.example.sinhanikita17.myapplication，PID：15127 java.lang.RuntimeException：无法启动活动ComponentInfo {com.example.sinhanikita17.myapplication / com.example.sinhanikita17.myapplication.Choose}：android.database.sqlite。 SQLiteException：没有这样的表：ICS（代码1）:,

公共类DatabaseHelper扩展了SQLiteOpenHelper { private static String DB_PATH;

private static String DB_NAME = "Courses.db";

private SQLiteDatabase myDataBase;

private final Context myContext;

private static final String LOGTAG = "Myapp5";
private static DatabaseHelper _dbHelper;

public DatabaseHelper(Context context) {

    super(context, DB_NAME, null, 1);
    this.myContext = context;


        DB_PATH =  "/data/data/" + context.getPackageName() + "/databases/";
    Log.i(LOGTAG, DB_PATH);
}

public static DatabaseHelper getInstance(Context context)
{
    if(_dbHelper == null)
    {
        _dbHelper = new DatabaseHelper(context);
    }
    return _dbHelper;
}

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");
        }
    }
}

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 doesn't exist yet.

    }

    if(checkDB != null) checkDB.close();

    return checkDB != null ? true : false;
}

private void copyDataBase() throws IOException{

    //Open your local db as the input stream
    InputStream myInput = myContext.getAssets().open("Courses.db");
    Log.i(LOGTAG, String.valueOf(myContext.getAssets()));

    // 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();

}

无法复制Android中的现有数据库

0 个答案: