基于Android SQLiteOpenHelper && CRUD 的使用_安卓软件开发教程-查字典教程网
基于Android SQLiteOpenHelper && CRUD 的使用
基于Android SQLiteOpenHelper && CRUD 的使用
发布时间:2016-12-28 来源:查字典编辑
摘要:复制代码代码如下:publicclassDBOpenHelperextendsSQLiteOpenHelper{//类没有实例化,不能用作父...

复制代码 代码如下:

public class DBOpenHelper extends SQLiteOpenHelper {

// 类没有实例化,不能用作父类构造器的参数,必须声明为静态

public DBOpenHelper(Context context, int version) {

super(context, "SQLite.db", null, version);

// 第三个参数CursorFactory指定在执行查询时获得一个游标实例的工厂类,设置为null代表使用系统默认的游标工厂;

}

@Override

public void onCreate(SQLiteDatabase db) {// 数据库第一次被创建的时候被调用,最开始创建数据库时赋的版本号值是0

// SQLiteDatabase用于生成数据库表;数据库存放路径:<package name>/databases/

db.execSQL("create table person(personid integer primary key autoincrement, name varchar(20))");

}

@Override

public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {// 版本号升级的时候进行调用;如果数据库不存在就不调用

db.execSQL("alter table person add phone varchar(12) null");// 往表中增加一列

}

}

DBOpenHelper dbOpenHelper = new DBOpenHelper(getContext(), 1);

dbOpenHelper.getWritableDatabase();// 会create数据库表or/open数据库表

public class PersonService {

private DBOpenHelper dbOpenHelper;

public PersonService(Context context) {

super();

this.dbOpenHelper = new DBOpenHelper(context, 2);

}

public void save(Person person) {

SQLiteDatabase db = dbOpenHelper.getWritableDatabase();

// SQLiteDatabase db2 = dbOpenHelper.getWritableDatabase();有缓存的功能,同一个Helper用此方法得到的对象为db;

db.execSQL("insert into person(name,phone) values(?,?)", new Object[] {person.getName(), person.getPhone() });

}

public void delete(Integer id) {

SQLiteDatabase db = dbOpenHelper.getWritableDatabase();

db.execSQL("delete from person where personid=?", new Object[] { id });

}

public void update(Person person) {

SQLiteDatabase db = dbOpenHelper.getWritableDatabase();

db.execSQL("update person set name=?,phone=? where personid=?",new Object[] { person.getName(), person.getPhone(),person.getId() });

}

public Person find(Integer id) {

SQLiteDatabase db = dbOpenHelper.getReadableDatabase();

// 如果数据库磁盘空间未满,得到的实例即为getWritableDatabase()得到的对象;因为此方法会调用getWritableDatabase方法;

Cursor cursor = db.rawQuery("select * from person where personid=?",new String[] { id.toString() });

if (cursor.moveToFirst()) {

int personid = cursor.getInt(cursor.getColumnIndex("personid"));

String name = cursor.getString(cursor.getColumnIndex("name"));

String phone = cursor.getString(cursor.getColumnIndex("phone"));

return new Person(personid, name, phone);

}

cursor.close();

return null;

}

/*

* 获取分页数据

*/

public List getScollData(int offest, int maxResult) {

List persons = new ArrayList();

SQLiteDatabase db = dbOpenHelper.getReadableDatabase();

Cursor cursor = db.rawQuery("select * from person order by personid asc limit ?,?",new String[] { String.valueOf(offest),String.valueOf(maxResult) });

while (cursor.moveToNext()) {

int personid = cursor.getInt(cursor.getColumnIndex("personid"));

String name = cursor.getString(cursor.getColumnIndex("name"));

String phone = cursor.getString(cursor.getColumnIndex("phone"));

persons.add(new Person(personid, name, phone));

}

cursor.close();

return persons;

}

public long getCount() {

SQLiteDatabase db = dbOpenHelper.getReadableDatabase();

Cursor cursor = db.rawQuery("select count(*) from person", null);

cursor.moveToFirst();

long result = cursor.getLong(0);

return result;

}

}

public class OtherPersonService {

private DBOpenHelper dbOpenHelper;

public OtherPersonService(Context context) {

super();

this.dbOpenHelper = new DBOpenHelper(context, 2);

}

public void save(Person person) {

SQLiteDatabase db = dbOpenHelper.getWritableDatabase();

ContentValues values = new ContentValues();// ContentValues 专门用于保存字段的值

values.put("name", person.getName());

values.put("phone", person.getPhone());

db.insert("person", null, values);// 第三个参数为字段值,第二个参数为空值字段,如果第三个参数为null

}

public void delete(Integer id) {

SQLiteDatabase db = dbOpenHelper.getWritableDatabase();

db.delete("person", "personid=?", new String[] { id.toString() });

}

public void update(Person person) {

SQLiteDatabase db = dbOpenHelper.getWritableDatabase();

ContentValues values = new ContentValues();

values.put("name", person.getName());

values.put("phone", person.getPhone());

db.update("person", values, "personid=?", new String[] { person.getId().toString() });

}

public Person find(Integer id) {

SQLiteDatabase db = dbOpenHelper.getReadableDatabase();

Cursor cursor = db.query("person", null, "personid=?",new String[] { id.toString() }, null, null, null);

if (cursor.moveToFirst()) {

int personid = cursor.getInt(cursor.getColumnIndex("personid"));

String name = cursor.getString(cursor.getColumnIndex("name"));

String phone = cursor.getString(cursor.getColumnIndex("phone"));

return new Person(personid, name, phone);

}

cursor.close();

return null;

}

/*

* 获取分页数据

*/

public List getScollData(int offest, int maxResult) {

List persons = new ArrayList();

SQLiteDatabase db = dbOpenHelper.getReadableDatabase();

Cursor cursor = db.query("person", null, null, null, null, null,"personid asc", offest + "," + maxResult);

//db.query(table, columns, selection, selectionArgs, groupBy, having, orderBy, limit);

while (cursor.moveToNext()) {

int personid = cursor.getInt(cursor.getColumnIndex("personid"));

String name = cursor.getString(cursor.getColumnIndex("name"));

String phone = cursor.getString(cursor.getColumnIndex("phone"));

persons.add(new Person(personid, name, phone));

}

cursor.close();

return persons;

}

public long getCount() {

SQLiteDatabase db = dbOpenHelper.getReadableDatabase();

Cursor cursor = db.query("person", new String[] { "count(*)" }, null, null, null, null, null);

//db.query(table, columns, selection, selectionArgs, groupBy, having, orderBy);

cursor.moveToFirst();

long result = cursor.getLong(0);

return result;

}

}

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