使用sqlite运行android程序时如何防止重复行

Question

您好，我正在为这两个问题苦苦挣扎： i) 我为我的 android 应用程序创建了 sqlite 数据库。并通过 Main Activity 添加行。现在，每当我运行我的程序时，每次都会在数据库中添加相同的行。如何确保只使用所有这些行创建一次数据库。 ii）我将 id（int 类型）设为主键并使其自动递增。我不希望主 ID 自动递增，并且可以为每一行手动设置。我该怎么做？

1. All database related functions have been in this code:
public class DataBaseHandlerActivity extends SQLiteOpenHelper {

    // Database Version
    private static final int DATABASE_VERSION = 1;

    // Database Name
    private static final String DATABASE_NAME = "shopsManager";

    // Shop table name
    private static final String TABLE_SHOPS = "shops";

    // Shop Table Columns names
    private static final String KEY_ID = "shopid";
    private static final String KEY_NAME = "shopname";
    private static final String KEY_ADDRESS = "shopaddress";
    private static final String KEY_CAT1="category1";
    private static final String KEY_CAT2="category2";
    private static final String KEY_CAT3="category3";
    private static final String KEY_CAT4="category4";
    private static final String KEY_IMAGE="shopimage";

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


    // Creating Tables
    @Override
    public void onCreate(SQLiteDatabase db) {

        String CREATE_SHOPS_TABLE="CREATE TABLE "+TABLE_SHOPS+"("+KEY_ID+" INTEGER PRIMARY KEY,"+KEY_NAME+" TEXT,"+
                KEY_IMAGE+" TEXT,"+
                KEY_ADDRESS+" TEXT,"+KEY_CAT1+" TEXT,"+KEY_CAT2+" TEXT,"+KEY_CAT3+" TEXT,"+KEY_CAT4+" TEXT"+
                ")";
        db.execSQL(CREATE_SHOPS_TABLE);

    }

    // Upgrading database
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // Drop older table if existed
        db.execSQL("DROP TABLE IF EXISTS"+TABLE_SHOPS);

        //CREATE TABLE AGAIN
        onCreate(db);


    }


    /**
     * All CRUD(Create, Read, Update, Delete) Operations
     */

    //Add a new shop row
    void addShop(Shop shop){
        SQLiteDatabase db=this.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(KEY_NAME,shop.getShopName());
        values.put(KEY_IMAGE,shop.getShopImage());
        values.put(KEY_ADDRESS,shop.getShopAddress());
        values.put(KEY_CAT1,shop.getShopCat1());
        values.put(KEY_CAT2,shop.getShopCat2());
        values.put(KEY_CAT3,shop.getShopCat3());
        values.put(KEY_CAT4,shop.getShopCat4());

        //Inserting row
        db.insert(TABLE_SHOPS,null,values);
        db.close(); //Close db connection
    }

    //Get a shop items corresponding to a primary key

    Shop getShop(int id){
        SQLiteDatabase db=this.getReadableDatabase();
        Cursor cursor=db.query(TABLE_SHOPS,new String[]{KEY_ID,KEY_NAME,KEY_IMAGE,KEY_ADDRESS,KEY_CAT1,KEY_CAT2,KEY_CAT3,KEY_CAT4},
                KEY_ID +"=?",new String[] { String.valueOf(id) }, null, null, null, null);
        if (cursor != null)
            cursor.moveToFirst();
       Shop shop = new Shop(Integer.parseInt(cursor.getString(0)),
                cursor.getString(1), cursor.getString(2),cursor.getString(3),cursor.getString(4),cursor.getString(5),
       cursor.getString(6),cursor.getString(7));
        // return shop
        return shop;
    }

    // Getting All Shops
    public List<Shop> getAllShops() {
        List<Shop> shopList = new ArrayList<Shop>();
        // Select All Query
        String selectQuery = "SELECT  * FROM " + TABLE_SHOPS;

        SQLiteDatabase db = this.getWritableDatabase();
        Cursor cursor = db.rawQuery(selectQuery, null);

        // looping through all rows and adding to list
        if (cursor.moveToFirst()) {
            do {
                Shop shop = new Shop();
                shop.setShopId(Integer.parseInt(cursor.getString(0)));
                shop.setShopName(cursor.getString(1));
                shop.setShopImage(cursor.getString(2));
                shop.setShopAddress(cursor.getString(3));
                shop.setShopCat1(cursor.getString(4));
                shop.setShopCat2(cursor.getString(5));
                shop.setShopCat3(cursor.getString(6));
                shop.setShopCat4(cursor.getString(7));
                // Adding contact to list
                shopList.add(shop);
            } while (cursor.moveToNext());
        }

        // return shop list
        return shopList;
    }

    // Updating single shop
    public int updateShop(Shop shop) {
        SQLiteDatabase db = this.getWritableDatabase();

        ContentValues values = new ContentValues();
        values.put(KEY_NAME,shop.getShopName());
        values.put(KEY_IMAGE,shop.getShopImage());
        values.put(KEY_ADDRESS,shop.getShopAddress());
        values.put(KEY_CAT1,shop.getShopCat1());
        values.put(KEY_CAT2,shop.getShopCat2());
        values.put(KEY_CAT3,shop.getShopCat3());
        values.put(KEY_CAT4,shop.getShopCat4());

        // updating row
        return db.update(TABLE_SHOPS, values, KEY_ID + " = ?",
                new String[] { String.valueOf(shop.getShopId()) });
    }

    // Deleting single shop
    public void deleteShop(Shop shop) {
        SQLiteDatabase db = this.getWritableDatabase();
        db.delete(TABLE_SHOPS, KEY_ID + " = ?",
                new String[] { String.valueOf(shop.getShopId()) });
        db.close();
    }


    // Getting shops Count
    public int getShopsCount() {
        String countQuery = "SELECT  * FROM " + TABLE_SHOPS;
        SQLiteDatabase db = this.getReadableDatabase();
        Cursor cursor = db.rawQuery(countQuery, null);
        int count=cursor.getCount();
        cursor.close();
        db.close() ;
        // return count
        return count;
    }


}

2。我传递数据以创建表的主要活动：

package com.trillbit.databaseactivity;

import android.database.sqlite.SQLiteDatabase;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;

import java.util.List;

public class MainActivity extends AppCompatActivity {


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        DataBaseHandlerActivity db=new DataBaseHandlerActivity(this);
/**
 * CRUD Operations
 * */
        // Inserting Shops
        Log.d("Insert: ", "Inserting ..");
        db.addShop(new Shop("Shoppers Stop","shopperstop","1st Floor,Forum Mall","Fashion","Clothes","Home","Shoes"));
        db.addShop(new Shop("LifeStyle", "lifestyle", "2nd Floor, Forum Mall", "Fashion", "Clothes","Home", "Mobile"));
        db.addShop(new Shop("Ezone", "ezone","3rd Floor, Forum Mall","Mobile","Electronics","Apppliances","Home"));
        db.addShop(new Shop("Dominos", "dominos","1st Floor,Forum Mall","Food","Pizza","Cake","Pastery"));

        // Reading all shops
        Log.d("Reading: ", "Reading all shops..");
        List<Shop> shops = db.getAllShops();
        for (Shop shop : shops) {
            String log = "Id: " + shop.getShopId() + " ,Name: " + shop.getShopName() + " ,Image: " + shop.getShopImage()
                    + ",Address: " + shop.getShopAddress() + ",Categort1: " + shop.getShopCat1() + ", Category2: " + shop.getShopCat2()
                    + ",Category3: " + shop.getShopCat3() + ",Catgeory4: " + shop.getShopCat4();
            // Writing Shops to log
            Log.d("Name: ", log);
        }


    }
}

3.logcat中的输出：

D/Name:: Id: 5 ,Name: Shoppers Stop ,Image: shopperstop,Address: 1st Floor,Forunm Mall,Categort1: Fashion, Category2: Clothes,Category3: Home,Catgeory4: Shoes
01-14 16:07:49.687 7993-7993/com.trillbit.databaseactivity D/Name:: Id: 6 ,Name: LifeStyle ,Image: lifestyle,Address: 2nd Floor, Forum Mall,Categort1: Fashion, Category2: Clothes,Category3: Home,Catgeory4: Mobile
01-14 16:07:49.687 7993-7993/com.trillbit.databaseactivity D/Name:: Id: 7 ,Name: Ezone ,Image: ezone,Address: 3rd Floor, Forum Mall,Categort1: Mobile, Category2: Electronics,Category3: Apppliances,Catgeory4: Home
01-14 16:07:49.687 7993-7993/com.trillbit.databaseactivity D/Name:: Id: 8 ,Name: Dominos ,Image: dominos,Address: 1st Floor,Forum Mall,Categort1: Food, Category2: Pizza,Category3: Cake,Catgeory4: Pastery
01-14 16:07:49.687 7993-7993/com.trillbit.databaseactivity D/Name:: Id: 9 ,Name: Shoppers Stop ,Image: shopperstop,Address: 1st Floor,Forum Mall,Categort1: Fashion, Category2: Clothes,Category3: Home,Catgeory4: Shoes
01-14 16:07:49.687 7993-7993/com.trillbit.databaseactivity D/Name:: Id: 10 ,Name: LifeStyle ,Image: lifestyle,Address: 2nd Floor, Forum Mall,Categort1: Fashion, Category2: Clothes,Category3: Home,Catgeory4: Mobile
01-14 16:07:49.687 7993-7993/com.trillbit.databaseactivity D/Name:: Id: 11 ,Name: Ezone ,Image: ezone,Address: 3rd Floor, Forum Mall,Categort1: Mobile, Category2: Electronics,Category3: Apppliances,Catgeory4: Home
01-14 16:07:49.687 7993-7993/com.trillbit.databaseactivity D/Name:: Id: 12 ,Name: Dominos ,Image: dominos,Address: 1st Floor,Forum Mall,Categort1: Food, Category2: Pizza,Category3: Cake,Catgeory4: Pastery

Answer 1

您每次创建 Activity 时都会添加这些行。

使用 SharedPreferences 标记一个布尔值，表明您的应用已启动一次

Answer 2

在数据库表定义中创建一个 UNIQUE CONSTRAINT。

它会自动防止重复条目。

或

代替

插入 ...

做

插入或忽略...

这意味着如果您违反约束，SQLite 不会返回错误代码，而是返回 SQLITE_OK，就好像命令成功一样。

Answer 3

为了其他人的利益，我正在写我如何使用 cricket-007 建议的共享偏好来解决问题。在主活动开始时，在应用程序安装并首次运行时创建数据库。

SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(this);
        if(!prefs.getBoolean("firstTime", false)) {
            // run your one time code
            // Inserting Shops

            Log.d("Insert: ", "Inserting ..");
            db.addShop(new Shop("01","Shoppers Stop","shopperstop","1st Floor,Forum Mall","Fashion","Clothes","Home","Shoes"));
            db.addShop(new Shop("02","LifeStyle", "lifestyle", "2nd Floor, Forum Mall", "Fashion", "Clothes","Home", "Mobile"));
            db.addShop(new Shop("03","Ezone", "ezone","3rd Floor, Forum Mall","Mobile","Electronics","Apppliances","Home"));
            db.addShop(new Shop("04","Dominos", "dominos","1st Floor,Forum Mall","Food","Pizza","Cake","Pastery"));
            SharedPreferences.Editor editor = prefs.edit();
            editor.putBoolean("firstTime", true);
            editor.commit();
        }