java - 未创建 SQLite 数据库文件

Question

SQLite 数据库文件 (.db) 未在 Android Device Monitor >DBMS >File Explore >data 中创建。此目录中没有显示 .db 文件。我发现自己无法弄清楚为什么没有创建数据库文件。这是我的文件。

MainActivity.java

package com.example.zohaib.database;

import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;

public class MainActivity extends AppCompatActivity {

    SQLiteOpenHelper sqLiteOpenHelper;
    SQLiteDatabase sqLiteDatabase;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        sqLiteOpenHelper = new DBConnection(this);
        sqLiteDatabase = sqLiteOpenHelper.getWritableDatabase();

    }
}

DBConnection.java

package com.example.zohaib.database;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
import android.widget.Toast;

public class DBConnection extends SQLiteOpenHelper {

    private static final int DATABASE_VERSION = 1;
    private static final String DATABASE_NAME = "products.db";
    private static final String TABLE_PRODUCTS = "products";
    private static final String COLUMN_ID = "id";
    private static final String COLUMN_PRODUCTNAME = "productName";



    public DBConnection(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
            String query ="CREATE TABLE " + TABLE_PRODUCTS + " (" +
                        COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
                        COLUMN_PRODUCTNAME + " TEXT " +
                        ")";
            db.execSQL(query);
            Log.d("Create Database:", "Successful");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_PRODUCTS);
        onCreate(db);
    }
}

Answer 1

您在一个创建表脚本中使用了两个表名。

改变

String query ="CREATE TABLE test_1 " + TABLE_PRODUCTS + " (" +
                    COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
                    COLUMN_PRODUCTNAME + " TEXT " +
                    ")";

到

String query ="CREATE TABLE " + TABLE_PRODUCTS + " (" +
                    COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
                    COLUMN_PRODUCTNAME + " TEXT " +
                    ");";