Android——另外一种增删查改的方式(ContentProvider常用)

以下介绍另外一种增删查改的方式

package com.njupt.sqllist;

import java.util.ArrayList;
import java.util.List;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;

public class PersonDao {

DBOpenHelper helper;

public PersonDao(Context context) {
helper = new DBOpenHelper(context);
}

public void insert(Person p) {
SQLiteDatabase db = helper.getWritableDatabase();

ContentValues values = new ContentValues();
values.put("name", p.getName());
values.put("balance", p.getBalance());
long row = db.insert("person", null, values);
System.out.println("在第"+row+"插入");
db.close();
}

public void delete(int id) {
SQLiteDatabase db = helper.getWritableDatabase();

int rows = db.delete("person", "id = ? ", new String[]{ id + ""});

System.out.println("删除了"+rows+"行");
db.close();
}

public void update(Person p) {
SQLiteDatabase db = helper.getWritableDatabase();
ContentValues values = new ContentValues();
values.put("name", p.getName());
values.put("balance", p.getBalance());
int rows = db.update("person", values,"id = ?",new String[]{p.getId() + ""});

System.out.println("更新了"+rows+"行");
db.close();
}

public Person query(int id) {
SQLiteDatabase db = helper.getReadableDatabase();

Cursor c = db.query("person", new String[]{"name,balance"}, "id = ? ", new String[]{id + ""}, null, null, null);
Person p = null;
if (c.moveToNext()) {
String name = c.getString(c.getColumnIndex("name"));
int balance = c.getInt(1);

p = new Person(id, name, balance);
}

System.out.println("这是一种另一种方式进行查询");
return p;
}

public List<Person> queryAll() {
SQLiteDatabase db = helper.getReadableDatabase();

Cursor c = db.query("person", null, null, null, null, null, null);

List<Person> persons = new ArrayList<Person>();

while (c.moveToNext()) {
Person p = new Person(c.getInt(0), c.getString(1), c.getInt(2));

persons.add(p);
}

System.out.println("这时再用另外一种方式查询所有");
return persons;
}

public void remit(int from, int to, int count) {
SQLiteDatabase db = helper.getWritableDatabase();
try {
db.beginTransaction();

db.execSQL("update person set balance = balance - ? where id = ?",
new Object[] { count, from });
System.out.println(1 / 0);
db.execSQL("update person set balance = balance + ? where id = ?",
new Object[] { count, to });

db.setTransactionSuccessful();
} finally {

db.endTransaction();
db.close();
}
}

public int queryCount() {
SQLiteDatabase db = helper.getReadableDatabase();

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

int count = c.getInt(0);

System.out.println("这时再用另外一种方式查询总数");
return count;
}

public List<Person> queryPage(int pageNum, int pageSize) {
SQLiteDatabase db = helper.getReadableDatabase();

Cursor c = db.query("person",null, null, null,null,null,null, (pageNum - 1) * pageSize + " , " + pageSize);
List<Person> persons = new ArrayList<Person>();

while (c.moveToNext()) {
Person p = new Person(c.getInt(0), c.getString(1), c.getInt(2));

persons.add(p);
}

System.out.println("这时再用另外一种方式在分页");
return persons;
}

}