Android学习笔记：使用sqlite实现登录验证

项目需求

（1）实现四个页面：首页、登录页、注册页、登陆成功页。

排版和跳转关系如图：

（2）注册页实现注册功能；登录页实现使用注册过的账号密码登录功能，登录成功后转到登录成功页；登录成功页有注销功能。

（3）具体功能：用户名必须为纯数字；注册页密码有二次验证功能；标题栏有返回键；成功登陆界面的文本根据用户名显示。

工程框架

主要实现代码

均在onActivityCreated（）方法实现，布局文件代码省略。

查看完整源码，请点击此处 没有的事

MainActivity

package com.example.myapplication;

import androidx.appcompat.app.ActionBar;
import androidx.appcompat.app.AppCompatActivity;
import androidx.navigation.NavController;
import androidx.navigation.Navigation;
import androidx.navigation.ui.NavigationUI;
import android.app.Activity;
import android.os.Bundle;
import android.view.MenuItem;
import android.view.Window;

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        NavController controller = Navigation.findNavController(this,R.id.fragment);
        NavigationUI.setupActionBarWithNavController(this,controller);
    }

    @Override
    public boolean onSupportNavigateUp(){
        NavController controller = Navigation.findNavController(this,R.id.fragment);
        return controller.navigateUp();
    }
}

user(首页)部分

public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);

       login_user = getView().findViewById(R.id.login_user);
        login_user.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View v){
                NavController controller = Navigation.findNavController(v);
                controller.navigate(R.id.action_user_to_login);
            }
        });

        register_user = getView().findViewById(R.id.register_user);
        register_user.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View v){
                NavController controller = Navigation.findNavController(v);
                controller.navigate(R.id.action_user_to_register);
            }
        });
    }

register（注册）部分

//对注册按钮监听
registerBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String name = name_register.getText().toString().trim();
                String password = password_register.getText().toString().trim();
                String repass = pass_register.getText().toString().trim();
                //连接数据库
                databaseHelper = new MyDatebaseHelper(getActivity(), DATABASE_NAME, null, DATABASE_VERSION);
                db = databaseHelper.getReadableDatabase();
                Cursor cursor = db.query(TABLE_NAME, new String[]{"name"}, "name=?", new String[]{name}, null, null, null);
                //判断账号是否全为数字
                    if (name.matches("[0-9]*")) {
                        //判断数据库中是否已有此账号
                        if (cursor != null && cursor.getCount() >= 1) {
                            Toast.makeText(getActivity(), "此用户已存在", Toast.LENGTH_LONG).show();
                            //刷新
                            NavController controller = Navigation.findNavController(v);
                            controller.navigate(R.id.action_register_self);
                        } else {
                            //判断输入框长度
                            if (!name.isEmpty() && !password.isEmpty() && !repass.isEmpty() && name.length() < 11 && password.length() < 11) {
                                if (password.equals(repass)) {
                                    //上传
                                    db.execSQL("insert into username (name,password) values(?,?)", new String[]{name, repass});
                                    Toast.makeText(getActivity(), "注册成功,请登录", Toast.LENGTH_LONG).show();
                                    //注册成功去到login界面
                                    NavController controller = Navigation.findNavController(v);
                                    controller.navigate(R.id.action_register_to_login);
                                } else {
                                    Toast.makeText(getActivity(), "两次密码不一致", Toast.LENGTH_SHORT).show();
                                }
                            } else {
                                Toast.makeText(getActivity(), "用户名和密码长度为1-10", Toast.LENGTH_SHORT).show();
                            }
                        }
                    } else {
                        Toast.makeText(getActivity(), "账号仅由数字组成", Toast.LENGTH_SHORT).show();
                    }
                }
        });
    }

login（登录）部分

loginBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String name = name_login.getText().toString().trim();
                String pass = pass_login.getText().toString().trim();
                if (!name.isEmpty() && !pass.isEmpty()) {
                    databaseHelper = new MyDatebaseHelper(getActivity(), DATABASE_NAME, null, DATABASE_VERSION);
                    db = databaseHelper.getReadableDatabase();
                    try {
                        Cursor cursor = db.query(TABLE_NAME, new String[]{"name", "password"}, "name=?", new String[]{name}, null, null, "password");
                        if (cursor != null && cursor.getCount() >= 1) {
                            while (cursor.moveToNext()) {
                                String password = cursor.getString(cursor.getColumnIndex("password"));
                                if (pass.equals(password)) {
                                    //弹出登录成功框
                                    new AlertDialog.Builder(getActivity()).setTitle("密码正确")
                                            .setMessage("成功登录").setPositiveButton("确定", new DialogInterface.OnClickListener() {
                                        @Override
                                        public void onClick(DialogInterface dialog, int which) {
                                            Bundle args = new Bundle();
                                            args.putString("username",name);
                                            NavController controller = Navigation.findNavController(v);
                                            controller.navigate(R.id.action_login_to_login_successful,args);

                                        }
                                    }).show();
                                    break;
                                } else {
                                    Toast.makeText(getActivity(), "密码错误", Toast.LENGTH_SHORT).show();
                                }
                            }
                        }else{
                            Toast.makeText(getActivity(), "该用户不存在", Toast.LENGTH_SHORT).show();
                        }
                    }catch (Exception e) {
                        e.printStackTrace();
                    }
                }else {
                    Toast.makeText(getActivity(), "请填写完整", Toast.LENGTH_SHORT).show();
                }
            }
        });

login_successful(登录成功页)部分

@Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        name_su = getView().findViewById(R.id.name_successful);

        //实现功能
        //传递login的name至此
        Intent intent = getActivity().getIntent();
        String name = intent.getStringExtra("name");
        name_su.setText(name);
        exitBtn = getView().findViewById(R.id.exitBtn);
        //接收name
        Bundle args = getArguments();
        String user = args.getString("username");
        //textView显示内容
        name_su.setText("欢迎您："+user);
        exitBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //注销，退出至首页
                NavController controller = Navigation.findNavController(v);
                controller.navigate(R.id.action_login_successful_to_user);
            }
        });
    }

数据库类

package com.example.myapplication;

import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import java.util.ArrayList;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;

class MyDatebaseHelper extends SQLiteOpenHelper {
    //数据库名称
    private static final String DATABASE_NAME="sql.db";
    //数据库版本号
    private static final int DATABASE_VERSION=1;
    //数据库SQL语句 添加一个表
    public MyDatebaseHelper(Context context, String name, CursorFactory factory, int version) {
        super(context, DATABASE_NAME, factory, DATABASE_VERSION);
        // TODO Auto-generated constructor stub
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        // TODO Auto-generated method stub
        db.execSQL("create table username( name varchar(30) primary key,password varchar(30))");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // TODO Auto-generated method stub
    }
}

标题栏自定义

左上方返回键

@Override
   protected void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.activity_main);
       NavController controller = Navigation.findNavController(this,R.id.fragment);
       NavigationUI.setupActionBarWithNavController(this,controller);
   }

   @Override
   public boolean onSupportNavigateUp(){
       NavController controller = Navigation.findNavController(this,R.id.fragment);
       return controller.navigateUp();
   }

属性

（1）设置标题栏的文字：在nav_graph_xml中，选中单个fragment，在Attributes中设置它的label即可。

（2）设置颜色：在themes.xml中找到<item name="colorPrimary">@color/purple_500</item>，在color.xml找到对应的<color name="purple_500">#FF00BFFF</color>，修改其中的颜色值即可。

总结

（1）可以增加登录输入验证码的功能。

（2）UI设计可以更加丰富。