本地数据库管理类

时间:2022-12-11 09:06:50

自定义继承SQLiteOpenHelper类

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

/**
* Created by Administrator on 2015/10/8.
*/

public class MySQLiteOpenHelper extends SQLiteOpenHelper {
public MySQLiteOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
super(context, name, factory, version);
}

public MySQLiteOpenHelper(Context context, String name) {
super(context, name,null,1);
}

@Override
public void onCreate(SQLiteDatabase db) {
//创建表,语句跟基本的SQL语句一样
db.execSQL("create table if not exists......");
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

}
}

创建DBManager类,由SQLiteOpenHelper单例得到SQLiteDatabase对象

import android.database.sqlite.SQLiteDatabase;
import com.test.administrator.myproject.BaseApplication;

/**
* Created by Administrator on 2015/10/12.
*/

public class DBManager {
private MySQLiteOpenHelper helper;
private SQLiteDatabase db;
private DBManager(){
//BaseApplication.getmBaseApplication()传入上下文
helper = new MySQLiteOpenHelper(BaseApplication.getmBaseApplication(),TableConfig.TABLE_NAME);
db = helper.getWritableDatabase();
}
private static DBManager manager;
public synchronized static DBManager newInstance(){
if (manager==null){
manager=new DBManager();
}
return manager;
}

public SQLiteDatabase getDb() {
return db;
}
}

创建DataBaseOperate类,仅以查询为例,遍历本地数据库数据

import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import java.lang.reflect.Field;
import java.util.ArrayList;
import java.util.List;

/**
* Created by Administrator on 2015/10/11.
*/

public class DataBaseOperate {

public static <T> List<T> getList(String tableName,Class<T> entityType ){
SQLiteDatabase db = DBManager.newInstance().getDb();//获得数据库
Cursor cursor = db.rawQuery("select * from "+tableName,null);//获得cursor
cursor.moveToFirst();
ArrayList<T> list = new ArrayList<>();//创建一个list用于存储表中所有数据
try {
while(!cursor.isAfterLast()){
T t = entityType.newInstance(); //通过反射获得Class对象
for(int i = 0;i<cursor.getColumnCount();i++)
{
String content = cursor.getString(i);//通过cursor指针获得i列的的name
String columnName = cursor.getColumnName(i);//通过cursor指针获得i列名称
Field field = entityType.getDeclaredField(columnName);//利用反射来通过列名获得属性
field.setAccessible(true);
field.set(t, content);//将获得的content值添加到t对象中
field.setAccessible(false);

}
cursor.moveToNext();
list.add(t); //将t添加到list中。
}
return list;
} catch (InstantiationException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (NoSuchFieldException e) {
e.printStackTrace();
}
/**
* 也可以直接使用xUtils中的dbUtils框架
*/

/*List<T> allWork = new ArrayList<>();
DbUtils utils = DbUtils.create(BaseApplication.getmBaseApplication(),tableName);
try {
allWork = utils.findAll(entityType);
} catch (DbException e) {
e.printStackTrace();
}
return allWork;*/

return null;
}
}