android--(SQLite)

/**
*
* 数据库元数据的定义 用于给 DatabaseHelper类使用
*
* 1.不能被继承 final
*
* 2.不能被创建 私有化构造函数
*
*
*/
public final class PetMetaData {

private PetMetaData() {

}

//定义表 表名和列名
public static abstract class DogTable implements BaseColumns {
public static final String TABLE_NAME = "dog";
public static final String NAME ="name";
public static final String AGE = "age";
}
}

// sqlite的助手类，程序第一次运行时，就自动创建数据库并可以维护数据库
public class DatabaseHelper extends SQLiteOpenHelper {

//定义数据库名称
private static String DB_NAME = "pet.db";

//版本号
private static int VERSION = 1;

//这里应该使用 定义元数据类的字段来拼接组成 sql语句，这里没有用
private static final String CREATE_TABLE_DOG = "CREATE TABLE dog(_id INTEGER PRIMARY KEY AUTOINCREMENT,name TEXT,age INTEGER)";

//删除表 应配合定义元数据的类拼接
private static final String DROP_TABLE_DOG ="DROP TABLE IF EXISTS dog";

public DatabaseHelper(Context context) {
super(context, DB_NAME, null, VERSION);
}

/***
* 如果数据库表不存在，那么用调用该方法
*
*
* @param db
*/
@Override
public void onCreate(SQLiteDatabase db) {

//SQLiteDatabase :用于操作数据库的工具类
db.execSQL(CREATE_TABLE_DOG);//如果表不存，则创建，存在，则不创建

}

/***
* 数据库 升级或更新
*
* @param db
* @param oldVersion
* @param newVersion
*/
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

db.execSQL(DROP_TABLE_DOG);//删除表

db.execSQL(CREATE_TABLE_DOG);//创建表，两句相当于更新表

}
}

/**
* 对数据库 增 删 改 查
*/
public class DataBaseAdapter {

private DatabaseHelper dbHelper;

public DataBaseAdapter(Context context) {
this.dbHelper = new DatabaseHelper(context);
}

/**
* 添加
*
* @param dog
*/
public void add(Dog dog) {

//获取 操作数据库的工具类
SQLiteDatabase db = dbHelper.getWritableDatabase();//检查数据库中有没有这个表，用于触发sqlite助手类创建表方法

//列数据对象
ContentValues values = new ContentValues();

//数据库元数据列名 所以应对象的值
values.put(PetMetaData.DogTable.NAME, dog.getName());
values.put(PetMetaData.DogTable.AGE, dog.getAge());

// 参数(表名，可为null的列名(保证 values 为空的时侯保证生成sql语名的合法性，
//     如果知道values不为null时，就填null)，ContentValues

//合法：insert into dog(name,age) values('xx',2)
//不合法： insert into dog() value()
db.insert(PetMetaData.DogTable.TABLE_NAME, null, values);
db.close();
}

/**
* 删除
*
* @param id
*/
public void delete(int id) {

SQLiteDatabase db = dbHelper.getWritableDatabase();

String whereclause = PetMetaData.DogTable._ID + "=?";
String[] whereargs = {String.valueOf(id)};

// 参数(表名,条件,条件的值)
db.delete(PetMetaData.DogTable.TABLE_NAME, whereclause, whereargs);
db.close();
}

/**
* 更新
*
* @param dog
*/
public void update(Dog dog) {

SQLiteDatabase db = dbHelper.getWritableDatabase();

ContentValues values = new ContentValues();
//数据库元数据列名 所以应对象的值
values.put(PetMetaData.DogTable.NAME, dog.getName());
values.put(PetMetaData.DogTable.AGE, dog.getAge());

String whereclause = PetMetaData.DogTable._ID + "=?";
String[] whereargs = {String.valueOf(dog.getId())};

//参数(表名,ContentValues,条件，条件的值)
db.update(PetMetaData.DogTable.TABLE_NAME, values, whereclause, whereargs);
db.close();

}

/**
* 根据id 查找 一个
*
* @param id
*/
public Dog findById(int id) {
SQLiteDatabase db = dbHelper.getReadableDatabase();

//要查询数据库的列名
String[] columns = {PetMetaData.DogTable._ID, PetMetaData.DogTable.NAME, PetMetaData.DogTable.AGE};

String selection = PetMetaData.DogTable._ID + "=?";
String[] selectionArgs = {String.valueOf(id)};

Cursor cursor = db.query(true, PetMetaData.DogTable.TABLE_NAME, columns, selection, selectionArgs, null, null, null, null);

Dog dog = null;
if (cursor.moveToNext()) {
dog = new Dog();
//通过 游标将元数据列名 所对应的值 填充到 对象的属性上
dog.setId(cursor.getInt(cursor.getColumnIndexOrThrow(PetMetaData.DogTable._ID)));
dog.setName(cursor.getString(cursor.getColumnIndexOrThrow(PetMetaData.DogTable.NAME)));
dog.setAge(cursor.getInt(cursor.getColumnIndexOrThrow(PetMetaData.DogTable.AGE)));
}
return dog;
}

/**
* 查找所有
*
* @return
*/
public ArrayList<Dog> findAll() {

SQLiteDatabase db = dbHelper.getReadableDatabase();

//要查询数据库的列名
String[] columns = {PetMetaData.DogTable._ID, PetMetaData.DogTable.NAME, PetMetaData.DogTable.AGE};

/**
* 参数：
* 1.是否去除重复记录
* 2.表名
* 3.要查询的列
* 4.查询条件
* 5.查询条件的值
* 6.分组条件
* 7.分组条件的值
* 8.排序
* 9.分页条件
*/
Cursor cursor = db.query(true, PetMetaData.DogTable.TABLE_NAME, columns, null, null, null, null, null, null);

ArrayList<Dog> dogs = new ArrayList<>();
Dog dog = null;

while (cursor.moveToNext()) {
dog = new Dog();
//通过 游标将元数据列名 所对应的值 填充到 对象的属性上
dog.setId(cursor.getInt(cursor.getColumnIndexOrThrow(PetMetaData.DogTable._ID)));
dog.setName(cursor.getString(cursor.getColumnIndexOrThrow(PetMetaData.DogTable.NAME)));
dog.setAge(cursor.getInt(cursor.getColumnIndexOrThrow(PetMetaData.DogTable.AGE)));

dogs.add(dog);
}

return dogs;
}

}

// 原生的写法
public class DataBaseAdapter {

private DatabaseHelper dbHelper;

public DataBaseAdapter(Context context) {
this.dbHelper = new DatabaseHelper(context);
}
/***
* 原生的sql 添加
*
* @param dog
*/
public void rawAdd(Dog dog) {
String sql = "insert into dog(name,age) values(?,?)";
Object[] args = {dog.getName(), dog.getAge()};

SQLiteDatabase db = dbHelper.getWritableDatabase();
db.execSQL(sql, args);
db.close();
}

/**
* 原生 sql 删除
*
* @param id
*/
public void rawDelete(int id) {
String sql = "delete from dog where _id=?";
Object[] args = {id};

SQLiteDatabase db = dbHelper.getWritableDatabase();
db.execSQL(sql, args);
db.close();
}

/***
* 原生sql 更新
*
* @param dog
*/
public void rawUpdate(Dog dog) {
String sql = "update dog set name =?,age=? where _id =?";
Object[] args = {dog.getName(), dog.getAge(), dog.getId()};

SQLiteDatabase db = dbHelper.getWritableDatabase();
db.execSQL(sql, args);
db.close();

}

/**
*  原生 sql查找一个
* @param id
* @return
*/
public Dog rawFindById(int id) {
String sql = "select _id,name,age,from dog where _id =?";

SQLiteDatabase db = dbHelper.getReadableDatabase();
Cursor cursor = db.rawQuery(sql, new String[]{String.valueOf(id)});

Dog dog = null;
if (cursor.moveToNext()) {
dog = new Dog();
//通过 游标将元数据列名 所对应的值 填充到 对象的属性上
dog.setId(cursor.getInt(cursor.getColumnIndexOrThrow(PetMetaData.DogTable._ID)));
dog.setName(cursor.getString(cursor.getColumnIndexOrThrow(PetMetaData.DogTable.NAME)));
dog.setAge(cursor.getInt(cursor.getColumnIndexOrThrow(PetMetaData.DogTable.AGE)));
}
return dog;

}

/***
*  原生sql 查找所有
* @return
*/
public ArrayList<Dog> rawFindAll() {

String sql = "select _id,name,age,from dog";

SQLiteDatabase db = dbHelper.getReadableDatabase();
Cursor cursor = db.rawQuery(sql, null);

ArrayList<Dog> dogs = new ArrayList<>();
Dog dog = null;

while (cursor.moveToNext()) {
dog = new Dog();
//通过 游标将元数据列名 所对应的值 填充到 对象的属性上
dog.setId(cursor.getInt(cursor.getColumnIndexOrThrow(PetMetaData.DogTable._ID)));
dog.setName(cursor.getString(cursor.getColumnIndexOrThrow(PetMetaData.DogTable.NAME)));
dog.setAge(cursor.getInt(cursor.getColumnIndexOrThrow(PetMetaData.DogTable.AGE)));

dogs.add(dog);
}

return dogs;
}
}

/**
* sql 事务的操作
*/
public void transaction() {
SQLiteDatabase db = dbHelper.getWritableDatabase();

//开始事务
db.beginTransaction();

try {
db.execSQL("insert into dog(name,age) values('dang',4)");
db.execSQL("insert into dog(name,age) values('do',5)");

db.setTransactionSuccessful();//设置事务成功的标记

} finally {
db.endTransaction();//结束事务，判断事务标记是否为true， 如果为true 那么就提交事务，否则回滚事务
db.close();
}
}