原因：找不到com.example.exampleCombant.Appname.Database：com / Database.class中找到com.example.example.appname.DataBase

Question

I can't run my app Because of this problem i have created an SQL lite data base using SQL lite Open Helper and added the table that i need but i can't run the app any help please? i have to finish the app on Sunday to give it to my teacher. I have tried to delete the app from my testing device and re installing it, and checked my app files but found nothing

package com.mohnad.theeducationnewera.marksbook;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

public class DataBase extends SQLiteOpenHelper {
    private static final String database_name = "DB";
    private static final int database_vesion =1;
    private static final String UID = "id";
    private static final String name = "Name";
    private static final String work_mark = "Works Mark";
    private static final String test_mark = "Tests mark";
    private static final String tableName = "Students";
    private Context context;
    private static final String DROP_TABLE = "DROP TABLE IF EXISTS " +tableName;
    private static final String CREATE_TABLE = "CREATE TABLE " +tableName+" " +
        " ("+UID+" INTEGER PRIMARY KEY AUTOINCREMENT," +
        " "+name+" TEXT VARCHAR(255))," +
        " "+work_mark+" INTEGER ," +
        " "+test_mark+" INTEGER ;";

    public DataBase(Context context) {
        super(context, database_name,null, database_vesion);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(CREATE_TABLE);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL(DROP_TABLE);
    }
}

Answer 1

first you must be sure that manifest have only one LAUNCHER

        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>

second in DBHelper

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    db.execSQL(DROP_TABLE);
//add line below
    onCreate(db);
}

give me the feed back after run it good luck