Android学习笔记-保存数据到SQL数据库中(Saving Data in SQL Databases)(2)
SQLiteDatabase db = this.getWritableDatabase();
db.delete(TABLE_CONTACTS, KEY_ID + " = ?",
new String[] { String.valueOf(contact.getID()) });
db.close();
改：update()方法
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_NAME, contact.getName());
values.put(KEY_PH_NO, contact.getPhoneNumber());
return db.update(TABLE_CONTACTS, values, KEY_ID + " = ?",
ew String[] { String.valueOf(contact.getID()) });
查：query()方法
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.query(TABLE_CONTACTS, new String[] { KEY_ID,
KEY_NAME, KEY_PH_NO }, KEY_ID + "=?",
new String[] { String.valueOf(id) }, null, null, null, null);
if (cursor != null)
cursor.moveToFirst();
Contact contact = new Contact(Integer.parseInt(cursor.getString(0)),
cursor.getString(1), cursor.getString(2));
return contact;
完整DatabaseHelper代码如下：
package com.example.sqlitetest;
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;
import android.database.sqlite.SQLiteOpenHelper;
public class DatabaseHelper extends SQLiteOpenHelper {
// 数据库版本
private static final int DATABASE_VERSION = 1;
// 数据库名
private static final String DATABASE_NAME = "contactsManager";
//Contact表名
private static final String TABLE_CONTACTS = "contacts";
//Contact表的列名
private static final String KEY_ID = "id";
private static final String KEY_NAME = "name";
private static final String KEY_PH_NO = "phone_number";
public DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
// 创建表
@Override
public void onCreate(SQLiteDatabase db) {
String CREATE_CONTACTS_TABLE = "CREATE TABLE " + TABLE_CONTACTS + "("
+ KEY_ID + " INTEGER PRIMARY KEY," + KEY_NAME + " TEXT,"
+ KEY_PH_NO + " TEXT" + ")";
db.execSQL(CREATE_CONTACTS_TABLE);
}
// 更新表
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// 删除旧表
db.execSQL("DROP TABLE IF EXISTS " + TABLE_CONTACTS);
//再次创建表
onCreate(db);
}
/**
*增删改查操作
*/
