我已经找到了一些关于这个主题的答案（例如this），但它不起作用。我只收到警告，它无法解析方法“openOrCreateDatabase(java.lang.String, int, null)”。
这是我的源代码：
public class DBHandler
{
SQLiteDatabase database;
DBHandler()
{
database = openOrCreateDatabase("DatabaseName", Context.MODE_PRIVATE, null);
}
}
【问题讨论】：
这是 SQLite 数据库和基本查询的完整代码。
public class SqliteHelper extends SQLiteOpenHelper {
private SQLiteDatabase db;
private Context mContext;
public static final String DATABASE_NAME = "DemoDB";
public static final int DATABASE_VERSION = 1;
public static final String TABLE_USERS = "users";
public static final String USER_ID = "id";
public static final String USER_NAME = "username";
public static final String USER_EMAIL = "email";
public static final String USER_PASSWORD = "password";
public static final String CREATE_QUERY_USER_TABLE = " CREATE TABLE " + TABLE_USERS
+ " ( "
+ USER_ID + " INTEGER PRIMARY KEY, "
+ USER_NAME + " TEXT, "
+ USER_EMAIL + " TEXT, "
+ USER_PASSWORD + " TEXT"
+ " ) ";
public SqliteHelper(@Nullable Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
mContext = context;
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(CREATE_QUERY_USER_TABLE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL(" DROP TABLE IF EXISTS " + TABLE_USERS);
}
// Method to openthe Database
public void openDataBase() throws SQLException {
db = getWritableDatabase();
}
// Method to close the Database
public void close() {
if (db != null && db.isOpen()) {
db.close();
}
}
public boolean isEmailExists(String email) {
boolean isUserFound = false;
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.rawQuery("SELECT * FROM users WHERE email = ?", new String[]{email.trim()});
if (cursor != null) {
if(cursor.getCount() > 0) {
isUserFound = true;
}
cursor.close();
}
return isUserFound;
}
public void addUser(User user) {
ContentValues values = new ContentValues();
values.put(USER_NAME, user.userName);
values.put(USER_EMAIL, user.email);
values.put(USER_PASSWORD, user.password);
long todo_id = db.insert(TABLE_USERS, null, values);
}
public boolean login(User user) {
boolean isLogin = false;
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.rawQuery("SELECT * FROM users WHERE email = ?", new String[]{user.email.trim()});
if (cursor != null) {
if (cursor.getCount() > 0 && cursor.moveToFirst()) {
String pass = cursor.getString(cursor.getColumnIndex(USER_PASSWORD));
if (pass != null && user.password.equalsIgnoreCase(pass.trim())) {
isLogin = true;
}
}
cursor.close();
}
return isLogin;
}
}
【讨论】：
创建“数据库”名称包并包含它
创建 SQLitHelper 名称类
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class SQLitHelper extends SQLiteOpenHelper {
public static final String DataBase_Name = "ABC";
public static final int Version = 1;
public static final String TblUser = "TblUser";
public static final String TblClassList = "TblClassList";
public static final String TblStudentList = "TblStudentList";
public SQLitHelper(Context context) {
super(context, DataBase_Name, null, Version);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("Create table " + TblUser +
"(id INTEGER PRIMARY KEY," +
"uid INTEGER," +
"fname TEXT," +
"lname TEXT," +
"email TEXT," +
"password TEXT," +
"teacher TEXT," +
"student TEXT," +
"parent TEXT," +
"status TEXT," +
"landing_page TEXT," +
"createdate TEXT," +
"birthdate TEXT," +
"profilepic TEXT," +
"phone TEXT," +
"address TEXT," +
"gender TEXT," +
"age TEXT," +
"googleid TEXT," +
"facebookid TEXT," +
"alert_time TEXT," +
"sch_name TEXT,"+
"login_with TEXT,"+
"default_zone TEXT)");
db.execSQL("Create table " + TblClassList +
"(id INTEGER PRIMARY KEY," +
"cid INTEGER," +
"uid INTEGER," +
"title TEXT," +
"color TEXT," +
"startdate TEXT," +
"enddate TEXT," +
"qrcode TEXT," +
"createdate TEXT," +
"not_submitted_count TEXT," +
"status TEXT," +
"extra1 TEXT," +
"extra2 TEXT)");
db.execSQL("Create table " + TblStudentList +
"(id INTEGER PRIMARY KEY," +
"uid INTEGER," +
"cid INTEGER," +
"fname TEXT," +
"lname TEXT," +
"email TEXT," +
"profilepic TEXT," +
"student_name TEXT," +
"isleader TEXT," +
"add_homework TEXT," +
"track_submission TEXT," +
"status TEXT," +
"edit_homework TEXT," +
"del_homework TEXT," +
"last_access TEXT)");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}
创建 DataHelper 类
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.util.Log;
import java.util.ArrayList;
import java.util.HashMap;
public class DataHelper {
SQLitHelper sqLitHelper;
SQLiteDatabase sqLiteDatabase;
Context context;
final String TAG = "DataHelper";
public DataHelper(Context context) {
sqLitHelper = new SQLitHelper(context);
this.context = context;
sqLiteDatabase = sqLitHelper.getWritableDatabase();
}
public void open() {
try {
sqLiteDatabase = sqLitHelper.getWritableDatabase();
} catch (Exception e) {
e.printStackTrace();
}
}
public void close() {
try {
sqLiteDatabase.close();
} catch (Exception e) {
e.printStackTrace();
}
}
public void insertUser(HashMap<String, String> list) {
ContentValues values = new ContentValues();
open();
try {
for (String str : list.keySet())
values.put(str, list.get(str));
long rowId = sqLiteDatabase.insert(SQLitHelper.TblUser, null, values);
} catch (Exception e) {
Log.e(TAG, "insertUser " + e.toString());
} finally {
close();
}
}
public void updateUser(HashMap<String, String> list, int uid) {
ContentValues values = new ContentValues();
open();
try {
for (String str : list.keySet())
values.put(str, list.get(str));
long rows = sqLiteDatabase.update(SQLitHelper.TblUser, values, "uid=" + uid, null);
} catch (Exception e) {
Log.e(TAG, "insertUser " + e.toString());
} finally {
close();
}
}
public int getUserRecordCount() {
int count = 0;
try {
open();
Cursor cursor = sqLiteDatabase.rawQuery("Select * from " + SQLitHelper.TblUser, null);
count = cursor.getCount();
cursor.close();
} catch (Exception e) {
Logger.debugLog(TAG, "userCount : " + e.toString());
} finally {
close();
}
return count;
}
public HashMap<String,String> getUserDetail(){
HashMap<String, String> list = new HashMap<>();
Cursor cursor = null;
try {
open();
cursor = sqLiteDatabase.rawQuery("SELECT * FROM " + SQLitHelper.TblUser, null);
if (cursor.getColumnCount() > 0) {
while (cursor.moveToNext()) {
list.put("uid", cursor.getString(cursor.getColumnIndex("uid")));
list.put("fname", cursor.getString(cursor.getColumnIndex("fname")));
list.put("lname", cursor.getString(cursor.getColumnIndex("lname")));
list.put("default_zone", cursor.getString(cursor.getColumnIndex("default_zone")));
list.put("teacher", cursor.getString(cursor.getColumnIndex("teacher")));
list.put("student", cursor.getString(cursor.getColumnIndex("student")));
list.put("parent", cursor.getString(cursor.getColumnIndex("parent")));
list.put("email", cursor.getString(cursor.getColumnIndex("email")));
list.put("gender", cursor.getString(cursor.getColumnIndex("gender")));
list.put("birthdate", cursor.getString(cursor.getColumnIndex("birthdate")));
list.put("profilepic", cursor.getString(cursor.getColumnIndex("profilepic")));
list.put("sch_name", cursor.getString(cursor.getColumnIndex("sch_name")));
list.put("login_with", cursor.getString(cursor.getColumnIndex("login_with")));
}
}
} catch (Exception e) {
Logger.debugLog(TAG, "getUserDetail : " + e.toString());
} finally {
close();
if (cursor != null)
if (!cursor.isClosed())
cursor.close();
}
return list;
}
public boolean deleteUserList() {
try {
open();
if (sqLiteDatabase.delete(SQLitHelper.TblUser, null, null) > 0){
return true;
}else {
return false;
}
} catch (Exception e) {
Logger.debugLog(TAG, "deleteUserList : " + e.toString());
} finally {
close();
}
return false;
}
public boolean insertClassList(MClassList mClassList) {
try {
open();
ContentValues contentValues = new ContentValues();
contentValues.put("cid", mClassList.getId());
contentValues.put("uid", mClassList.getUid());
contentValues.put("title", mClassList.getTitle());
contentValues.put("color", mClassList.getColor());
contentValues.put("startdate", mClassList.getStartdate());
contentValues.put("enddate", mClassList.getEnddate());
contentValues.put("qrcode", mClassList.getQrcode());
contentValues.put("createdate", mClassList.getCreatedate());
contentValues.put("status", mClassList.getStatus());
contentValues.put("not_submitted_count", mClassList.getNot_sub_count());
long id = sqLiteDatabase.insert(SQLitHelper.TblClassList, null, contentValues);
Logger.debugLog(TAG, "insertClassList : Sus");
return true;
} catch (Exception e) {
Logger.debugLog(TAG, "insertClassList : " + e.toString());
} finally {
close();
}
return false;
}
public ArrayList<MClassList> getClassList() {
ArrayList<MClassList> clssArrayList = new ArrayList<>();
Cursor cursor = null;
try {
open();
String Query = QueryBuilder.classListQuery();
cursor = sqLiteDatabase.rawQuery(Query, null);
if (cursor.getColumnCount() > 0) {
while (cursor.moveToNext()) {
MClassList mClassList = new MClassList();
mClassList.setId(cursor.getInt(cursor.getColumnIndex("cid")));
mClassList.setUid(cursor.getInt(cursor.getColumnIndex("uid")));
mClassList.setTitle(cursor.getString(cursor.getColumnIndex("title")));
mClassList.setColor(cursor.getString(cursor.getColumnIndex("color")));
mClassList.setStartdate(cursor.getString(cursor.getColumnIndex("startdate")));
mClassList.setEnddate(cursor.getString(cursor.getColumnIndex("enddate")));
mClassList.setQrcode(cursor.getString(cursor.getColumnIndex("qrcode")));
mClassList.setCreatedate(cursor.getString(cursor.getColumnIndex("createdate")));
mClassList.setStatus(cursor.getString(cursor.getColumnIndex("status")));
mClassList.setNot_sub_count(cursor.getString(cursor.getColumnIndex("not_submitted_count")));
clssArrayList.add(mClassList);
}
}
} catch (Exception e) {
Logger.debugLog(TAG, "getClassList : " + e.toString());
} finally {
close();
if (cursor != null)
if (!cursor.isClosed())
cursor.close();
}
return clssArrayList;
}
public boolean deleteClassList() {
try {
open();
if (sqLiteDatabase.delete(SQLitHelper.TblClassList, null, null) > 0){
return true;
}else {
return false;
}
} catch (Exception e) {
Logger.debugLog(TAG, "deleteClassList : " + e.toString());
} finally {
close();
}
return false;
}
public boolean deleteStudentList() {
try {
open();
if (sqLiteDatabase.delete(SQLitHelper.TblStudentList, null, null) > 0){
return true;
}
else{
return false;
}
} catch (Exception e) {
Logger.debugLog(TAG, "deleteStudentList : " + e.toString());
} finally {
close();
}
return false;
}
public void deleteStudent(int cid,int uid) {
try {
open();
sqLiteDatabase.delete(SQLitHelper.TblStudentList, "uid=" + uid + " AND cid=" + cid, null);
} catch (Exception e) {
Logger.debugLog(TAG, "deleteStudent : " + e.toString());
} finally {
close();
}
}
}
创建类 QueryBuilder
public class QueryBuilder {
public static String teacherABCList(int cid) {
Calendar c = Calendar.getInstance();
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
String formatDate = df.format(c.getTime()).toString();
String Query = "SELECT * FROM " + SQLitHelper.TblTeacherHomeworkAll + " WHERE cid='" + cid + "'" + " AND duedate>= " +"'"+ formatDate+"'" + " ORDER BY duedate DESC ";
return Query;
}
==============================
public static String studentXXXListQuery(int uid,String status) {
Calendar c = Calendar.getInstance();
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
String formatDate = df.format(c.getTime()).toString();
String Query = "SELECT * FROM " + SQLitHelper.TblStudentHomeworkAll + " WHERE uid='" + uid + "'" + " AND status= " +"'"+ status+"'"+" AND isDone='N'" + " ORDER BY duedate DESC ";
return Query;
}
===========================================
public static String studentListQuery(String questionID) {
String query = "SELECT * FROM " + SQLitHelper.TblStudentCheckAnswer + " WHERE qid=" + questionID;
return query;
}
}
【讨论】：
这是我的代码如何使用 sqlite 数据库
DatabaseHelper.java
public class DatabaseHelper extends SQLiteOpenHelper {
public DatabaseHelper(Context context) {
super(context, "loginDB.db", null, 1);
getWritableDatabase();
}
@Override
public void onCreate(SQLiteDatabase sqLiteDatabase) {
String query = "create table registration (id INTEGER,Image BLOB,firstname VARCHAR,Lastname VARCHAR,DateOfBirth VARCHAR,Phone VARCHAR,Gender VARCHAR, Email VARCHAR primary key,Password VARCHAR);";
sqLiteDatabase.execSQL(query);
}
@Override
public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {
}
//method for insert data
public boolean insertRecord(byte[] imageInByte,String fn) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues contentValues = new ContentValues();
contentValues.put("Image", imageInByte);
contentValues.put("Firstname", fn);
db.insert("signup", null, contentValues);
return true;
}
public boolean updaterecord(String fn,String ln,String unme){
SQLiteDatabase db = this.getWritableDatabase();
ContentValues contentValues = new ContentValues();
contentValues.put("Firstname", fn);
contentValues.put("Lastname", ln);
contentValues.put("Username", unme);
return db.update(TABLE_NAME, contentValues, "Username = ?", new String[]{(unme)}) > 0;
}
public boolean deleterecord(String FirstName) {
SQLiteDatabase db = this.getWritableDatabase();
return db.delete(TABLE_NAME, "Firstname = ?", new String[]{FirstName}) > 0;
}
public int displayDetail(String email, String password) {
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery("select * from registration where Email='" + email + "'AND Password='" + password + "'", null);
return cursor.getCount();
}
public ArrayList displayDetails(String email, String password) {
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery("select * from registration where Email='" + email + "'AND Password='" + password + "'", null);
ArrayList<ModelClass> arrayList = new ArrayList();
ModelClass model;
if (cursor != null) {
if (cursor.getCount() > 0) {
while (cursor.moveToNext()) {
model = new Model();
model.setFirstname(cursor.getString(cursor.getColumnIndex("Firstname")));
model.setLastname(cursor.getString(cursor.getColumnIndex("Lastname")));
arrayList.add(model);
}
}
}
return arrayList;
}
}
【讨论】：
将数据保存到sqlite中，首先在main中使用
public class MainActivity extends AppCompatActivity {
String one,two;
EditText name,phone;
Button saveButton;
List<StudentModel> list = new ArrayList<StudentModel>();
DatabaseHelper db;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
db = new DatabaseHelper(getApplicationContext());
saveButton=(Button)findViewById(R.id.submit);
name=(EditText)findViewById(R.id.textName);
phone=(EditText)findViewById(R.id.textPhone);
saveButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
StudentModel student = new StudentModel();
student.name = name.getText().toString();
student.phone_number = phone.getText().toString();
db.addStudentDetail(student);
list = db.getAllStudentsList();
print(list);
}
});
}
private void print(List<StudentModel> list) {
String value = "";
for(StudentModel sm : list){
value = value+"id: "+sm.id+", name: "+sm.name+" Ph_no: "+sm.phone_number+"\n";
}
Log.i("<<<<<<<<<<",value);
}
}
然后创建处理程序类
public class DatabaseHelper extends SQLiteOpenHelper {
// Database Name
public static String DATABASE_NAME = "student_database";
private static final int DATABASE_VERSION = 1;
private static final String TABLE_STUDENTS = "students";
private static final String KEY_ID = "id";
private static final String KEY_NAME = "name";
private static final String KEY_PHONENUMBER = "phone_number";
public static String TAG = "tag";
private static final String CREATE_TABLE_STUDENTS = "CREATE TABLE "
+ TABLE_STUDENTS + "(" + KEY_ID
+ " INTEGER PRIMARY KEY AUTOINCREMENT," + KEY_NAME + " TEXT,"
+ KEY_PHONENUMBER + " TEXT );";
public DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(CREATE_TABLE_STUDENTS);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + CREATE_TABLE_STUDENTS);
onCreate(db);
}
public long addStudentDetail(StudentModel student) {
SQLiteDatabase db = this.getWritableDatabase();
// Creating content values
ContentValues values = new ContentValues();
values.put(KEY_NAME, student.name);
values.put(KEY_PHONENUMBER, student.phone_number);
// insert row in students table
long insert = db.insert(TABLE_STUDENTS, null, values);
return insert;
}
public int updateEntry(StudentModel student) {
SQLiteDatabase db = this.getWritableDatabase();
// Creating content values
ContentValues values = new ContentValues();
values.put(KEY_NAME, student.name);
values.put(KEY_PHONENUMBER, student.phone_number);
return db.update(TABLE_STUDENTS, values, KEY_ID + " = ?",
new String[] { String.valueOf(student.id) });
}
public void deleteEntry(long id) {
SQLiteDatabase db = this.getWritableDatabase();
db.delete(TABLE_STUDENTS, KEY_ID + " = ?",
new String[] { String.valueOf(id) });
}
public StudentModel getStudent(long id) {
SQLiteDatabase db = this.getReadableDatabase();
String selectQuery = "SELECT * FROM " + TABLE_STUDENTS + " WHERE "
+ KEY_ID + " = " + id;
Log.d(TAG, selectQuery);
Cursor c = db.rawQuery(selectQuery, null);
if (c != null)
c.moveToFirst();
StudentModel students = new StudentModel();
students.id = c.getInt(c.getColumnIndex(KEY_ID));
students.phone_number = c.getString(c.getColumnIndex(KEY_PHONENUMBER));
students.name = c.getString(c.getColumnIndex(KEY_NAME));
return students;
}
public List<StudentModel> getAllStudentsList() {
List<StudentModel> studentsArrayList = new ArrayList<StudentModel>();
String selectQuery = "SELECT * FROM " + TABLE_STUDENTS;
Log.d(TAG, selectQuery);
SQLiteDatabase db = this.getReadableDatabase();
Cursor c = db.rawQuery(selectQuery, null);
if (c.moveToFirst()) {
do {
StudentModel students = new StudentModel();
students.id = c.getInt(c.getColumnIndex(KEY_ID));
students.phone_number = c.getString(c
.getColumnIndex(KEY_PHONENUMBER));
students.name = c.getString(c.getColumnIndex(KEY_NAME));
studentsArrayList.add(students);
} while (c.moveToNext());
}
return studentsArrayList;
}
}
然后设置并获取值
public class StudentModel {
public int id;
public String name;
public String phone_number;
public StudentModel(int id, String name, String phone_number) {
// TODO Auto-generated constructor stub
this.id = id;
this.name = name;
this.phone_number = phone_number;
}
public StudentModel(){
}
}
试试看
【讨论】：
使用以下示例创建数据库
import android.content.ContentValues;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
import com.ayconsultancy.sumeshmedicals.SumeshMedicalContext;
import com.ayconsultancy.sumeshmedicals.model.PlaceModel;
import com.ayconsultancy.sumeshmedicals.utils.Utils;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.ArrayList;
/**
* Created by Admin33 on 16-02-2016.
*/
public class DBHelper extends SQLiteOpenHelper {
static String DATABASE_NAME = "sumesh_medicals";
static int DATABASE_VERSION = 1;
static DBHelper dbHelperInstance;
static SQLiteDatabase db;
public DBHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
public static DBHelper getInstance() {
if (dbHelperInstance == null) {
dbHelperInstance = new DBHelper(SumeshMedicalContext.getContext());
}
return dbHelperInstance;
}
@Override
public void onCreate(SQLiteDatabase db) {
Utils.ShowLogD("in sqlite oncreate");
try {
db.execSQL(DBQueries.CREATE_OTC_TABLE);
db.execSQL(DBQueries.CREATE_SHOP_DETAILS_TABLE);
db.execSQL(DBQueries.CREATE_USER_DETAILS_TABLE);
db.execSQL(DBQueries.CREATE_CITY_TABLE);
} catch (Exception e) {
e.printStackTrace();
}
// insertIntoShopDetails(db);
// insertIntoOTcPrescrion(db);
}
public synchronized SQLiteDatabase getDababase() {
if (db == null || (db != null && !db.isOpen())) {
db = this.getWritableDatabase();
}
return db;
}
public synchronized void close() {
super.close();
if (db != null)
db.close();
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}
【讨论】：
正如评论者给您的示例一样，您需要创建 SQLiteOpenHelper 类的子类并覆盖将创建数据库和表的 onCreate 和 onUpgrade 方法。然后你可以使用这个帮助类的方法 getReadableDatabase( ) 或 getWritableDatabase( ) 来获取 SQLite 数据库的副本。您可以对此对象执行查询。 下面的代码 sn-p 演示了它。
public class DBAdapter {
private SQLiteDatabase database;
private Context context;
private DatabaseHelper dbHelper;
private class DatabaseHelper extends SQLiteOpenHelper {
public DatabaseHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
super(context, name, factory, version);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(CREATE_TABLES_QUERY);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXIST "+TABLE_QUERY);
}
}
public DBAdapter(Context ctx) {
this.context = ctx;
}
public DBAdapter open() throws SQLException {
dbHelper = new DatabaseHelper(context, DBNAME, null,DBVERSION);
database = dbHelper.getWritableDatabase();
return this;
}
public Cursor executeQuery() {
Cursor result = database.rawQuery(YOUR_QUERY, null);
return result;
}
}
使用SQLite Open Helper developers guide 获取更多帮助。
希望对你有帮助。
【讨论】：
public class Sqlhelper extends SQLiteOpenHelper {
private SQLiteDatabase db;
public static final String KEY_ROWID = "_id";
public static final String KEY_FNAME = "firstname";
Sqlhelper DB = null;
private static final String DATABASE_NAME = "dbname.db";
private static final int DATABASE_VERSION = 2;
public static final String DATABASE_TABLE_NAME = "db";
private static final String DATABASE_TABLE_CREATE =
"CREATE TABLE " + DATABASE_TABLE_NAME + "(" +
"_id INTEGER PRIMARY KEY AUTOINCREMENT,"+
"firstname TEXT NOT NULL);";
public Sqlhelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
try{
db.execSQL(DATABASE_TABLE_CREATE);
Log.d("DATABASE", "Table Was Created");
}catch(Exception e){
e.printStackTrace();
}
}
public void open() {
getWritableDatabase();
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
onCreate(db);
Log.d("DATABASE", "Table Was UPDATED");
}
【讨论】：
SQLite 是一个开源 SQL 数据库，可将数据存储到设备上的文本文件中。 Android 带有内置的 SQLite 数据库实现。
请查看以下链接
结构
public class MySQLiteHelper extends SQLiteOpenHelper {
public static final String TABLE_COMMENTS = "comments";
public static final String COLUMN_ID = "_id";
public static final String COLUMN_COMMENT = "comment";
private static final String DATABASE_NAME = "commments.db";
private static final int DATABASE_VERSION = 1;
// Database creation sql statement
private static final String DATABASE_CREATE = "create table "
+ TABLE_COMMENTS + "(" + COLUMN_ID
+ " integer primary key autoincrement, " + COLUMN_COMMENT
+ " text not null);";
public MySQLiteHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase database) {
database.execSQL(DATABASE_CREATE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
Log.w(MySQLiteHelper.class.getName(),
"Upgrading database from version " + oldVersion + " to "
+ newVersion + ", which will destroy all old data");
db.execSQL("DROP TABLE IF EXISTS " + TABLE_COMMENTS);
onCreate(db);
}
}
【讨论】：