Android数据存储之SQLite数据库

//创建名叫test.db的数据库（如果不存在就创建它，如果存在就打开它）
SQLiteDatabase db=openOrCreateDatabase(getFilesDir()+"/test.db",Context.MODE_PRIVATE,null);
//删除名为test.db的数据库
deleteDatabase(getFilesDir()+"/test.db");

package USER_CLASS;

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

import java.util.ArrayList;

/**
 * Created by animator on 2020/1/18.
 */
public class UserDBHelper extends SQLiteOpenHelper {
    private static final String DB_NAME="user.db";//数据库名称
    private static final int DB_VERSION=1;//数据库版本号
    private static UserDBHelper mHelper=null;//数据库帮助类的示例
    private SQLiteDatabase mDB=null;//数据库的示例
    public final String TABLE_NAME="user_info";//表的名称

    private UserDBHelper(Context context){
        super(context,DB_NAME,null,DB_VERSION);
    }

    private UserDBHelper(Context context,int version){
        super(context,DB_NAME,null,version);
    }

    //利用单例模式获取数据库帮助器的唯一实例
    public static UserDBHelper getInstance(Context context,int version){
        if(version>0&&mHelper==null){
            mHelper=new UserDBHelper(context,version);
        }else if(mHelper==null){
            mHelper=new UserDBHelper(context);
        }
        return mHelper;
    }

    //打开数据库的读连接
    public SQLiteDatabase openReadLink(){
        if(mDB==null||!mDB.isOpen()){
            mDB=mHelper.getReadableDatabase();
        }
        return mDB;
    }
    //打开数据库的写连接
    public SQLiteDatabase openWriteLink(){
        if(mDB==null||!mDB.isOpen()){
            mDB=mHelper.getWritableDatabase();
        }
        return mDB;
    }
    //关闭数据库的连接
    public void closeLink(){
        if(mDB!=null&&mDB.isOpen()){
            mDB.close();
            mDB=null;
        }
    }

    //创建数据库，执行建表语句
    @Override
    public void onCreate(SQLiteDatabase sqLiteDatabase) {
        String drop_sql="DROP TABLE IF EIXSTS"+TABLE_NAME+";";
        sqLiteDatabase.execSQL(drop_sql);
        String create_sql="CREATE TABLE IF NOT EXISTS"+TABLE_NAME+"("+
                "_id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,"+
                "name VARCHAR NOT NULL,"+"age INTEGER NOT NULL,"+
                "height LONG NOT NULL,"+"weight FLOAT NOT NULL,"+
                "married INTEGER NOT NULL,"+"update_time VARCHAR NOT NULL,"+
                "phone VARCHAR,"+"password VARCHAR"+");";
        sqLiteDatabase.execSQL(create_sql);
    }


    //修改数据库，执行表结构变更语句
    @Override
    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {

    }

    //根据指定条件删除表记录
    public int delete(String condition){
        //执行删除记录动作，该语句返回删除记录的数目
        return mDB.delete(TABLE_NAME,condition,null);
    }

    //往该表中添加多条记录
    public long insert(ArrayList<UserInfo> infoArray){
        long result=-1;
        for(int i=0;i<infoArray.size();i++){
            UserInfo info=infoArray.get(i);
            ArrayList<UserInfo> tempArray=new ArrayList<UserInfo>();
            //如果存在同样的手机号码，则更新记录
            //注意条件语句的等号后面要用单引号括起来
            if(info.phone!=null&&info.phone.length()>0){
                String condition=String.format("phone=‘%s‘",info.phone);
                tempArray=query(condition);
                if(tempArray.size()>0){
                    update(info,condition);
                    result=tempArray.get(0).rowid;
                    continue;
                }
            }
            //不存在唯一性重复的记录，则插入新记录
            ContentValues cv=new ContentValues();
            cv.put("name",info.name);
            cv.put("age",info.age);
            cv.put("height",info.height);
            cv.put("weight",info.weight);
            cv.put("married",info.married);
            cv.put("update_time",info.update_time);
            cv.put("phone",info.phone);
            cv.put("password",info.password);
            //执行插入记录的动作，该语句返回插入记录的行号
            result=mDB.insert(TABLE_NAME,"",cv);
            //添加成功后返回行号，失败后返回-1
            if(result==-1)
                return result;
        }
        return result;
    }

    //根据条件更新指定的表记录
    public int update(UserInfo info,String condition){
        ContentValues cv=new ContentValues();
        cv.put("name",info.name);
        cv.put("age",info.age);
        cv.put("height",info.height);
        cv.put("weight",info.weight);
        cv.put("married",info.married);
        cv.put("update_time",info.update_time);
        cv.put("phone",info.phone);
        cv.put("password",info.password);
        //执行更新记录动作，该语句返回记录更新的数目
        return mDB.update(TABLE_NAME,cv,condition,null);
    }

    //根据指定条件查询记录，并返回结果数据队列
    public ArrayList<UserInfo> query(String condition){
        String sql=String.format("select rowid,_id,name,age,height,weight,married,update_time,phone,password from %s where %s",TABLE_NAME,condition);
        ArrayList<UserInfo> infoArray=new ArrayList<UserInfo>();
        //执行记录查询动作，该语句返回结果集的游标
        Cursor cursor=mDB.rawQuery(sql,null);
        //循环取出游标指向的每条记录
        while(cursor.moveToNext()){
            UserInfo info=new UserInfo();
            info.rowid=cursor.getLong(0);
            info.xuhao=cursor.getInt(1);
            info.name=cursor.getString(2);
            info.age=cursor.getInt(3);
            info.height=cursor.getLong(4);
            info.weight=cursor.getFloat(5);
            //SQLite没有boolean型，用0表示false用1表示true
            info.married=(cursor.getInt(6)==0)?false:true;
            info.update_time=cursor.getString(7);
            info.phone=cursor.getString(8);
            info.password=cursor.getString(9);
            infoArray.add(info);
        }
        cursor.close();
        return infoArray;
    }

    //根据手机号码查询指定记录
    public UserInfo queryByPhone(String phone){
        UserInfo info=null;
        ArrayList<UserInfo> infoArray= query(String.format("phone=‘%s‘",phone));
        if(infoArray.size()>0){
            info=infoArray.get(0);
        }
        return info;
    }
}