Android数据库Sqlite的基本用法及升级策略

package com.ninetripods.mq.sqliteupdatedemo.db; import android.content.ContentValues; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; import com.ninetripods.mq.sqliteupdatedemo.MyApplication; import com.ninetripods.mq.sqliteupdatedemo.bean.Student; import java.util.ArrayList; import java.util.List; /** * Created by mq on 2017/10/22 上午11:36 * mqcoder90@gmail.com */ public class DBDao { public static final String TABLE_NAME = "student";//表名 private static final String ID = "id";//id自增长 private static final String NAME = "stu_name";//姓名 private static final String AGE = "stu_age";//年龄 private static final String SEX = "stu_sex";//性别 private static final String GRADE = "stu_grade";//年级 //DB_Version2增加新字段 private static final String SCORE = "store"; private DBHelper dbHelper; //创建表结构 public static final String SQL_CREATE_TABLE = "create table " + TABLE_NAME + "(" + ID + " integer primary key autoincrement," + NAME + " text," + AGE + " integer," + SEX + " varchar(5)," + GRADE + " text" + ")"; private DBDao() { dbHelper = new DBHelper(MyApplication.getContext()); } public static DBDao getInstance() { return InnerDB.instance; } private static class InnerDB { private static DBDao instance = new DBDao(); } /** * 数据库插入数据 * * @param bean 实体类 * @param <T> T */ public synchronized <T> void insert(T bean) { SQLiteDatabase db = dbHelper.getWritableDatabase(); try { if (bean != null && bean instanceof Student) { Student student = (Student) bean; ContentValues cv = new ContentValues(); cv.put(NAME, student.getName()); cv.put(AGE, student.getAge()); cv.put(SEX, student.getSex()); cv.put(GRADE, student.getGrade()); cv.put(SCORE, student.getStore()); db.insert(TABLE_NAME, null, cv); } } catch (Exception e) { e.printStackTrace(); } finally { db.close(); } } /** * 删除表中所有的数据 */ public synchronized void clearAll() { SQLiteDatabase db = dbHelper.getWritableDatabase(); String sql = "delete from " + TABLE_NAME; try { db.execSQL(sql); } catch (Exception e) { e.printStackTrace(); } finally { db.close(); } } /** * 查询数据 * * @return List */ public synchronized <T> List<T> query() { SQLiteDatabase db = dbHelper.getReadableDatabase(); List<T> list = new ArrayList<>(); String querySql = "select * from " + TABLE_NAME; Cursor cursor = null; try { cursor = db.rawQuery(querySql, null); while (cursor.moveToNext()) { Student student = new Student(); student.setName(cursor.getString(cursor.getColumnIndex(NAME))); student.setAge(cursor.getInt(cursor.getColumnIndex(AGE))); student.setSex(cursor.getString(cursor.getColumnIndex(SEX))); student.setGrade(cursor.getString(cursor.getColumnIndex(GRADE))); student.setStore(cursor.getString(cursor.getColumnIndex(SCORE))); list.add((T) student); } } catch (Exception e) { e.printStackTrace(); } finally { if (cursor != null) { cursor.close(); } if (db != null) { db.close(); } } return list; } }