Android/app/src/main/java/com/example/Cat/activity/MainActivity.java

package com.example.Cat.activity;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import com.example.Cat.R;
import com.example.Cat.databaseoperation.User_Database;
import com.example.Cat.entity.UserInfo;

import java.util.List;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
    private Button registerButton, loginButton;
    private EditText usernameText, paswdEdit;
    List<UserInfo> list ;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        User_Database user=new User_Database(MainActivity.this);
        SQLiteDatabase sqLiteDatabase=user.getReadableDatabase();

        setContentView(R.layout.user_login);
        init();
    }

    private void init() {
        usernameText = findViewById(R.id.username);
        paswdEdit = findViewById(R.id.password);
        loginButton = findViewById(R.id.login);
        loginButton.setOnClickListener(this);
        registerButton = findViewById(R.id.register);
        registerButton.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.register:
                Intent intent = new Intent(MainActivity.this, RegisterActivity.class);
                startActivity(intent);
                break;
            case R.id.login:
                Verification();
                break;
        }
    }

    //验证密码是否正确
    public void Verification(){
        //UserInfo info;
        Intent intent = new Intent(MainActivity.this, UserActivity.class);
        //intent.putExtra("username",usernameText.getText().toString());
        User_Database user=new User_Database(MainActivity.this);
        SQLiteDatabase sqLiteDatabase=user.getReadableDatabase();
        UserInfo info=user.queryByName(sqLiteDatabase,usernameText.getText().toString());
        //info=list.get(0);
        if(info!=null){
            intent.putExtra("username",usernameText.getText().toString());
            if(paswdEdit.getText().toString().equals(info.getPaswd())){
                startActivity(intent);
            }
            else{
                Toast.makeText(this, "密码错误！", Toast.LENGTH_SHORT).show();
            }
        }
        else{
            Toast.makeText(this, "用户不存在！", Toast.LENGTH_SHORT).show();
        }
    }
}