SQLite数据库实用的封装

SQLite数据库简单封装:

每一张表 都会对应一个Bean 和一个Dao类

SqliteHelper 主要负责创建数据库和更新数据库 主要为其提供 创建表的sql语句 数据库名称 和数据库版本号

SqliteHelper类

public class SqliteHelper extends SQLiteOpenHelper {
private static String DB_NAME="gac.db";
private static int VERSION = 1;
private static final String USER_TABLE_CREATE="create table if not exists "
+UserDao.TABLE_NAME +" ("
+UserDao.COLUMN_ID +" INTEGER PRIMARY KEY AUTOINCREMENT, "
+UserDao.COLUMN_NAME+" TEXT)";
private Context context;
private static SqliteHelper instance;
public static SqliteHelper getInstance(Context context){
if(instance == null){
instance = new SqliteHelper(context.getApplicationContext());
}
return instance;
}
public SqliteHelper(Context context){
super(context,DB_NAME,null,VERSION);
this.context = context;
}
public Context getContext(){
return context;
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(USER_TABLE_CREATE);
}

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

}
public void closeDB(){
if(instance != null){
try{
SQLiteDatabase db = instance.getWritableDatabase();
db.close();
}catch (Exception e){
e.printStackTrace();
}
instance = null;

}
}
}

bean类主要负责 对应表 成员变量最好和表的字段名对应

public class UserBean {
public String name;
public int id;
public UserBean(){

}
public UserBean(String name){
this.name = name;
}
public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

public int getId() {
return id;
}

public void setId(int id) {
this.id = id;
}
}

4.dao类主要负责操作对应的表的增删该查 以及存储表的字段名 和表的名称 添加的数据可以利用反射进行操作

public class UserDao {
public static String TABLE_NAME = "user";
public static String COLUMN_ID = "id";
public static String COLUMN_NAME = "name";
private SqliteHelper helper = null;

public UserDao(Context context){
helper = new SqliteHelper(context);
}

//根据cursor获取userbean
private UserBean getUserBeanByCursor(Cursor cursor){
UserBean user = new UserBean();
Class< ? extends UserBean> clazz = user.getClass();
Field[] fields = clazz.getDeclaredFields();
for(Field field :fields){
if(field.getName().equals("id")){
user.id = cursor.getInt(cursor.getColumnIndex("id"));
continue;
}
if(field.getName().equals("name")){
user.name = cursor.getString(cursor.getColumnIndex("name"));
continue;
}
}
return user;
}

//根据user获取contentvalues
private ContentValues getContentValues(UserBean user){
ContentValues values = new ContentValues();
Class<? extends  UserBean> clazz = user.getClass();
try{
Method[] methods = clazz.getMethods();
Object[] args = null;
for(Method method : methods) {
String mName = method.getName();
if (mName.startsWith("get") && !mName.startsWith("getClass")) {
String filedName = mName.substring(3, mName.length()).toLowerCase();
Log.e("gac","fieldName:"+filedName);
if(filedName.equals("id")){
//id 让它自动增加
continue;
}
Object value = method.invoke(user, args);
if (value instanceof String) {
values.put(filedName, (String) value);
} else if (value instanceof Integer) {
values.put(filedName, (Integer) value);
}
}
}
}catch (Exception e){e.printStackTrace();}
return values;
}

//添加用户
public boolean addUser(UserBean user){
boolean flag = false;
SQLiteDatabase database = null;
long id = -1;
try{
database = helper.getWritableDatabase();
ContentValues values = getContentValues(user);
Class<? extends  UserBean> calzz = user.getClass();
String tableName = TABLE_NAME;
id = database.insert(tableName,null,values);
flag = (id !=-1?true:false);
if(database != null){
database.close();
}
}catch (Exception e){
e.printStackTrace();
}
Log.e("gac","addUser flag:"+flag);
return flag;
}

//删除用户
public boolean delteUser(String id,String name){
boolean flag = false;
String wereClause = "id = ? and name = ?";

String [] whereArgs = new String[]{id,name};
SQLiteDatabase db = helper.getWritableDatabase();
try{
int res = db.delete(TABLE_NAME,wereClause,whereArgs);
flag = (res != 0?true:false);
if(db != null){
db.close();
}
}catch (Exception e){
e.printStackTrace();
}
return flag;
}

//更新数据库
public boolean updateUser(String whereClause,String[] whereArgs,UserBean user){
//        String wereClause = "id = ? and name = ?";
//        String [] whereArgs = new String[]{id,name};
boolean flag = false;
SQLiteDatabase db = helper.getWritableDatabase();
try{
ContentValues values = getContentValues(user);
int res = db.update(TABLE_NAME,values,whereClause,whereArgs);
flag = (res <= 0?false:true);
db.close();
}catch (Exception e){e.printStackTrace();}
Log.e("gac","updateUser:"+flag);
return flag;
}

//查询
public List<UserBean>  getUserList(String sql,String[] whereArgs){
SQLiteDatabase db = helper.getWritableDatabase();
Cursor cursor = db.rawQuery(sql, whereArgs);
List<UserBean> mList = null;
if(cursor != null){
mList = new ArrayList<>();
while (cursor.moveToNext()){
mList.add(getUserBeanByCursor(cursor));
}
}
return mList;
}

}

//测试例子

//new UserDao(this).addUser(new UserBean("gac"));
// new UserDao(this).updateUser("id = ?",new String[]{1+""},new UserBean("gac1"));
List<UserBean> list = new UserDao(this).getUserList("select * from " + UserDao.TABLE_NAME, null);
for(int i =0; i < list.size(); i++){
Log.e("gac",list.get(i).getName());
Log.e("gac",list.get(i).getId()+"");
}