android SQLite实现本地登录注册功能,SQLite简单应用（android studio）
16lz
2021-01-24
目录
SQLite简单用法介绍
使用 SQL 操作数据库
添加数据的方法如下：
更新数据的方法如下：
删除数据的方法如下：
查询数据的方法如下：
本地实现登陆注册效果图：
实现代码
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SQLite简单用法介绍
SQLite基本用法很简单，继承SQLiteOpenHelper 中有两个抽象方法，分别是onCreate()和 onUpgrade()，我们必须在自己的帮助类里面重写这两个方法，然后分别在这两个方法中去实现创建、升级数据库的逻辑。
SQLiteOpenHelper 中 还 有 两 个 非 常 重 要 的 实 例 方 法 ， getReadableDatabase() 和getWritableDatabase()。
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使用 SQL 操作数据库
添加数据的方法如下：
db.execSQL("insert into Book (name, author, pages, price) values(?, ?, ?, ?)",new String[] { "The Da Vinci Code", "Dan Brown", "454", "16.96" }); db.execSQL("insert into Book (name, author, pages, price) values(?, ?, ?, ?)",new String[] { "The Lost Symbol", "Dan Brown", "510", "19.95" });
更新数据的方法如下：
db.execSQL("update Book set price = ? where name = ?", new String[] { "10.99","The Da Vinci Code" });
删除数据的方法如下：
db.execSQL("delete from Book where pages > ?", new String[] { "500" });
查询数据的方法如下：
db.rawQuery("select * from Book", null);-
本地实现登陆注册效果图：
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实现代码
OpenHelper类
public class OpenHelper extends SQLiteOpenHelper { //建表语句 public static final String CREATE_USER = "create table User (" + "id integer primary key autoincrement, " + "username text, " + "userpwd text)"; public OpenHelper(Context context, String name, CursorFactory factory, int version) { super(context, name, factory, version); // TODO Auto-generated constructor stub } @Override public void onCreate(SQLiteDatabase db) { // TODO Auto-generated method stub db.execSQL(CREATE_USER);//创建用户表 } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { // TODO Auto-generated method stub }}SqliteDB类：
public class SqliteDB { /** * 数据库名 */ public static final String DB_NAME = "sqlite_dbname"; /** * 数据库版本 */ public static final int VERSION = 1; private static SqliteDB sqliteDB; private SQLiteDatabase db; private SqliteDB(Context context) { OpenHelper dbHelper = new OpenHelper(context, DB_NAME, null, VERSION); db = dbHelper.getWritableDatabase(); } /** * 获取SqliteDB实例 * @param context */ public synchronized static SqliteDB getInstance(Context context) { if (sqliteDB == null) { sqliteDB = new SqliteDB(context); } return sqliteDB; } /** * 将User实例存储到数据库。 */ public int saveUser(User user) { if (user != null) { /* ContentValues values = new ContentValues(); values.put("username", user.getUsername()); values.put("userpwd", user.getUserpwd()); db.insert("User", null, values);*/ Cursor cursor = db.rawQuery("select * from User where username=?", new String[]{user.getUsername().toString()}); if (cursor.getCount() > 0) { return -1; } else { try { db.execSQL("insert into User(username,userpwd) values(?,?) ", new String[]{user.getUsername().toString(), user.getUserpwd().toString()}); } catch (Exception e) { Log.d("错误", e.getMessage().toString()); } return 1; } } else { return 0; } } /** * 从数据库读取User信息。 */ public List loadUser() { List list = new ArrayList(); Cursor cursor = db .query("User", null, null, null, null, null, null); if (cursor.moveToFirst()) { do { User user = new User(); user.setId(cursor.getInt(cursor.getColumnIndex("id"))); user.setUsername(cursor.getString(cursor .getColumnIndex("username"))); user.setUserpwd(cursor.getString(cursor .getColumnIndex("userpwd"))); list.add(user); } while (cursor.moveToNext()); } return list; } public int Quer(String pwd,String name) { HashMap hashmap=new HashMap(); Cursor cursor =db.rawQuery("select * from User where username=?", new String[]{name}); // hashmap.put("name",db.rawQuery("select * from User where name=?",new String[]{name}).toString()); if (cursor.getCount()>0) { Cursor pwdcursor =db.rawQuery("select * from User where userpwd=? and username=?",new String[]{pwd,name}); if (pwdcursor.getCount()>0) { return 1; } else { return -1; } } else { return 0; } }} User类：
package model;/** * Created by Administrator on 2015/11/10. */public class User { private int id; public int getId() { return id; } public void setId(int id) { this.id = id; } public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getUserpwd() { return userpwd; } public void setUserpwd(String userpwd) { this.userpwd = userpwd; } private String username; private String userpwd;}
LoginActivity：package activity;import android.os.Bundle;import android.support.v7.app.AppCompatActivity;import android.view.View;import android.widget.Button;import android.widget.EditText;import android.widget.TextView;import com.example.administrator.sqlitetest.R;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import model.SqliteDB;import model.User;public class LoginActivity extends AppCompatActivity { private Button reg; private Button login; private EditText count; private EditText pwd; private TextView state; private List userList; private List dataList = new ArrayList<>(); @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_login); reg= (Button) findViewById(R.id.regin); login= (Button) findViewById(R.id.login); count= (EditText) findViewById(R.id.count); pwd= (EditText) findViewById(R.id.pwd); state= (TextView) findViewById(R.id.state); reg.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { String name=count.getText().toString().trim(); String pass=pwd.getText().toString().trim(); User user=new User(); user.setUsername(name); user.setUserpwd(pass); int result=SqliteDB.getInstance(getApplicationContext()).saveUser(user); if (result==1){ state.setText("注册成功！"); }else if (result==-1) { state.setText("用户名已经存在！"); } else { state.setText("！"); } } }); login.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { String name=count.getText().toString().trim(); String pass=pwd.getText().toString().trim(); //userList=SqliteDB.getInstance(getApplicationContext()).loadUser(); int result=SqliteDB.getInstance(getApplicationContext()).Quer(pass,name); if (result==1) { state.setText("登录成功！"); } else if (result==0){ state.setText("用户名不存在！"); } else if(result==-1) { state.setText("密码错误！"); }/* for (User user : userList) { if (user.getUsername().equals(name)) { if (user.getUserpwd().equals(pass)) { state.setText("登录成功！"); }else { state.setText("密码错误！"); } } else { state.setText("用户名不存在！"); } }*/ } }); }}
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