Question

数据丢失后，我会从资产中复制数据库

这是android studio，可以从资产中复制数据库

错误是=没有这样的表：tbltexts（代码1 SQLITE_ERROR）：，而在编译时：SELECT * FROM tbltexts

我的dbname = texts.db

此错误是在ANDROID PIE上

public class Databasehelper extends SQLiteOpenHelper {

    public static String DB_PATH = "/data/data/com.nooshindroid.Rosary/databases/";
    public static final String DATABASE_NAME = "texts.db";
    private static final int DATABASE_VERSION = 1;
    public static final String tblname ="tbltexts";
    public static final String id="id";
    public static final String arabic ="Arabic_text";
    public static final String english ="English_text";
    public static final String counter ="Counter";
    public static final String goal ="Goal";
    private Context context;
    private SQLiteDatabase database;
    public Databasehelper(Context context) {
        super(context, DATABASE_NAME, null,DATABASE_VERSION);
             this.context = context;

    }

    @Override
    public void onCreate(SQLiteDatabase db) {

    }

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

    }
    public void copyDataBase() throws IOException {
        InputStream myInput = context.getAssets().open(DATABASE_NAME);
        String outFileName = DB_PATH + DATABASE_NAME;
        OutputStream myOutput = new FileOutputStream(outFileName);
        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 class DbHandler {


    private SQLiteDatabase database;
    private  String name;
    private Databasehelper dbHelper;
    public DbHandler(Context context){
        dbHelper=new Databasehelper(context);
    }
    public void open(){
        database=dbHelper.getWritableDatabase();
    }

    public  void close(){
       database.close();
    }

    public String display(int row,int field){

        Cursor cursor=database.query(dbHelper.tblname,null,null,null,null,null,null,null);
            cursor.moveToPosition(row);
           name=cursor.getString(field);
        return name;
    }



    public boolean insert(String txtarab,String txtenglish,int goal) {

        ContentValues cv = new ContentValues();
        cv.put(dbHelper.arabic, txtarab);
        cv.put(dbHelper.english, txtenglish);
        cv.put(dbHelper.goal,goal);
        long result = database.insert(dbHelper.tblname, null, cv);
        database.close();

        if (result == -1) {
            return false;
        } else {
            return true;
        }
    }

    public Integer count(){
        Cursor cursor=database.query(dbHelper.tblname,null,null,null,null,null,null);
        int s=cursor.getCount();
        return s;
    }
    public void delete(int id){
        database.delete(dbHelper.tblname,"id="+id,null);
    }
    public void update(String arab, String englsih, int id){
        ContentValues contentValues=new ContentValues();
        contentValues.put(dbHelper.arabic,arab);
        contentValues.put(dbHelper.english,englsih);
        database.update(dbHelper.tblname,contentValues,"id="+id,null);
    }

    public void counterupdate(int id,int counter){
        ContentValues contentValues=new ContentValues();
        contentValues.put(dbHelper.counter,counter);
        database.update(dbHelper.tblname,contentValues,"id="+id,null);
    }

}

Answer 1

您不应该对数据库路径进行硬编码，没有保证它将是/data/data/<package_id>/databases，例如，在我的手机（Android Pie，API 26）上，它是/data/user/<user_id>/<package_id>/databases。该文档甚至警告说，路径可能会改变，因为应用程序可以移动到采用的存储中。

如果路径错误（并且捕获了copyDataBase()的异常），您将得到SQLiteOpenHelper自动创建的空数据库。

一种解决方案是替换：

String outFileName = DB_PATH + DATABASE_NAME;

与：

String outFileName = context.getDatabasePath(DATABASE_NAME);

复制sqlite后丢失数据

1 个答案: