2021年1月26日 sqlite数据库

今天学习了sqlite数据库，更新了工程

StarbuzzDatabaseHelper：

package bjfu.it.sun.starbuzz;


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

import static android.icu.lang.UProperty.NAME;

public class StarbuzzDatabaseHelper extends SQLiteOpenHelper {
    private static final String DB_NAME = "starbuzz.db";//数据库的名称
    private static final int DB_VERSION = 2;//数据库的版本号

    //StarbuzzDatabaseHelper的默认的构造函数，必须提供构造函数，制定数据库名和版本
    public StarbuzzDatabaseHelper(Context context ){
        super(context,DB_NAME,null,DB_VERSION);
}
 @Override
    public void onCreate(SQLiteDatabase db) {
        //创建表
        db.execSQL("CREATE TABLE DRINK(_id INTEGER PRIMARY KEY AUTOINCREMENT,"
                +"NAME TEXT,"
                +"DESCRIPTION TEXT,"
                +"IMAGE_RESOURCE_ID INTEGER);"
        );
        //插入咖啡的信息,3条数据
     insertDrink(db,"Latte","A couple of espresso shots with steames milk",R.drawable .coffee1 );
     insertDrink(db,"Cappuccino","Espresso,hot milk,and a steamed milk foam",R.drawable.coffee2);
     insertDrink(db,"Filter","Highest quality beans roasted and brewed fresh",R.drawable.coffee3);

    }
    public static void insertDrink (SQLiteDatabase db,String name,String description,int resourceld){
        ContentValues drinkValues=new ContentValues();
        drinkValues.put("NAME",name);
        drinkValues.put("DESCRIPTION",description );
        drinkValues.put("IMAGE_RESOURCE_ID",resourceld );

        long result=db.insert("DRINK",null,drinkValues) ;

        Log.d ("sqlite","insert"+name+",_id"+result );

    }
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        if(oldVersion <=1){
            //NUMERIC这种值可以代表bool类型
            db.execSQL("ALTER TABLE DRINK ADD COLUMN FAVORITE NUMERIC;");
        }
    }
}

DrinkActivity：

package bjfu.it.sun.starbuzz;

import androidx.appcompat.app.AppCompatActivity;

import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
import android.os.Bundle;
import android.util.Log;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

public class DrinkActivity extends AppCompatActivity {
    public static final String EXTRA_DRINKID="drinkId";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_drink);
       //从inrent中取出数组的索引
        int drinkId=getIntent().getIntExtra(EXTRA_DRINKID ,0) ;
//        Drink drink=Drink.drinks[drinkId];
//
//        //显示咖啡照片
//        ImageView photo=findViewById(R.id.photo );
//        photo.setImageResource(drink.getImageResourceId() ) ;
//        photo.setContentDescription(drink.getName() ) ;
//
//
//        //显示咖啡名称
//        TextView name=findViewById(R.id.name );
//        name.setText(drink.getName() );
//
//        //显示咖啡的描述
//        TextView description =findViewById(R.id.description ) ;
//        description.setText(drink.getDescription() );

        //实例化一个helper对象，
        SQLiteOpenHelper starbuzzDataBaseHelper=new StarbuzzDatabaseHelper(this);

//        //获得数据引用
//        SQLiteDatabase db=starbuzzDataBaseHelper.getReadableDatabase() ;

        try( SQLiteDatabase db=starbuzzDataBaseHelper.getReadableDatabase()){
            //YOYO读取数据库
        }catch(SQLiteException e){
            Log.e("sqlite",e.getMessage());
            Toast toast =Toast.makeText(this,"database unavailable",Toast.LENGTH_SHORT);
            toast.show() ;
            //若出现错误，用log.e打印error级的日志， 并弹出toast提示
    }
}
}