java - Android Pie没有从服务器我的sql数据库中获取数据

Question

我正在尝试从存储在服务器中的数据库中获取数据。在其他 android 版本中一切正常，但应用程序未在 android 9 中获取数据。在 android 9 中处理数据库是否还有其他要求。

这是数据库助手类

public class DBHelper extends SQLiteOpenHelper {

//database version
private static int db_version = 1;

//database name
private static String db_name = "quiz_level.db";

//database path string
private String db_path;


private SQLiteDatabase db;
private final Context context;

//table name
public static String TABLE_NAME = "level";

//column names

public static String CATE_ID = "cat_id";
public static String SUB_CATE_ID = "sub_cat_id";
public static String LEVEL_NO = "level_no";


public DBHelper(Context context) {
    super(context, db_name, null, db_version);
    this.context = context;

    File database = context.getDatabasePath(db_name);
    if (!database.exists()) {
        // Database does not exist so copy it from assets here
        db_path = context.getDatabasePath(db_name).toString().replace(db_name, "");

    } else {
        //if database  exist get database from path
    db_path = context.getDatabasePath(db_name).toString();

    }

}

@Override
public SQLiteDatabase getReadableDatabase() {
    return super.getReadableDatabase();
}

@Override
public SQLiteDatabase getWritableDatabase() {
    return super.getWritableDatabase();
}

@Override
public void onCreate(SQLiteDatabase db) {

}
@Override
public void onOpen(SQLiteDatabase db) {
    super.onOpen(db);
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {
        db.disableWriteAheadLogging();
    }
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

}

//delete database
public void db_delete() {
    File file = new File(db_path + db_name);
    if (file.exists()) {
        file.delete();

    }
}

//Create a empty database on the system
public void createDatabase() throws IOException {
    boolean dbExist = checkDataBase();

    if (dbExist) {
        Log.v("DB Exists", "db exists");

    }

    boolean dbExist1 = checkDataBase();
    if (!dbExist1) {
        this.getWritableDatabase();
        try {
            this.close();
            copyDataBase();
        } catch (IOException e) {
            throw new Error("Error copying database");
        }
    }
}

//Check database already exist or not
private boolean checkDataBase() {
    boolean checkDB = false;
    try {
        String myPath = db_path + db_name;
        File dbfile = new File(myPath);
        checkDB = dbfile.exists();
    } catch (SQLiteException e) {
    }
    return checkDB;
}

//Copies your database from your local assets-folder to the just created empty database in the system folder
private void copyDataBase() throws IOException {
    String outFileName = db_path + db_name;
    OutputStream myOutput = new FileOutputStream(outFileName);
    InputStream myInput = context.getAssets().open(db_name);

    byte[] buffer = new byte[1024];
    int length;
    while ((length = myInput.read(buffer)) > 0) {
        myOutput.write(buffer, 0, length);
    }
    myInput.close();
    myOutput.flush();
    myOutput.close();
}

/*
 * insert level no
 */
public void insertIntoDB(int cat_id, int sub_cat_id, int level_no) {
    SQLiteDatabase db = this.getWritableDatabase();
    String query = "INSERT INTO " + TABLE_NAME + " (" + CATE_ID + "," + SUB_CATE_ID + "," + LEVEL_NO + ") VALUES('" + cat_id + "', '" + sub_cat_id + "', '" + level_no + "');";
    db.execSQL(query);

}

/*
 *with this method we check if categoryId & subCategoryId is already exist or not in our database
 */
public boolean isExist(int cat_id, int sub_cat_id) {
    db = this.getReadableDatabase();
    Cursor cur = db.rawQuery("SELECT * FROM " + TABLE_NAME + " WHERE ( " + CATE_ID + " = " + cat_id + " AND " + SUB_CATE_ID + " = " + sub_cat_id + ")", null);
    boolean exist = (cur.getCount() > 0);
    cur.close();
    System.out.println("---isExit  " + (cur.getCount() > 0));
    return exist;

}

/*
 * get level
 */
public int GetLevelById(int cat_id, int sub_cat_id) {
    int level = 1;
    String selectQuery = "SELECT  * FROM " + TABLE_NAME + " WHERE  (" + CATE_ID + "=" + cat_id + " AND " + SUB_CATE_ID + "=" + sub_cat_id + ")";
    SQLiteDatabase db = this.getReadableDatabase();
    Cursor c = db.rawQuery(selectQuery, null);
    // looping through all rows and adding to list
    if (c.moveToFirst()) {
        do {
            level = c.getInt(c.getColumnIndex(LEVEL_NO));
        } while (c.moveToNext());
    }
    return level;
}

/*
 * Update lavel
 */
public void UpdateLevel(int cat_id, int sub_cat_id, int level_no) {
    db = this.getReadableDatabase();

    db.execSQL("update " + TABLE_NAME + " set level_no=" + level_no + " where (cat_id =" + cat_id + "  and  " + sub_cat_id + " = " + sub_cat_id + ")");
}}

我还在学习，所以任何帮助都将不胜感激，因为它是我在 android 中的第一个项目。谢谢

标签： javaandroidmysql