个人学习app
loginactivity.java

package com.example.studyapp;



import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import androidx.appcompat.app.AppCompatActivity;

public class LoginActivity extends AppCompatActivity {
    private EditText editTextUserId;
    private Button buttonLogin, buttonRegister;
    private DatabaseHelper dbHelper;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);

        dbHelper = new DatabaseHelper(this);

        editTextUserId = findViewById(R.id.editTextUserId);
        buttonLogin = findViewById(R.id.buttonLogin);
        buttonRegister = findViewById(R.id.buttonRegister);

        buttonLogin.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String userId = editTextUserId.getText().toString().trim();

                if (userId.isEmpty()) {
                    Toast.makeText(LoginActivity.this, "请输入学号", Toast.LENGTH_SHORT).show();
                    return;
                }

                if (dbHelper.checkUser(userId)) {
                    User user = dbHelper.getUser(userId);
                    Intent intent = new Intent(LoginActivity.this, MainActivity.class);
                    intent.putExtra("USER_ID", user.getUserId());
                    intent.putExtra("USERNAME", user.getUsername());
                    intent.putExtra("PHONE", user.getPhone());
                    intent.putExtra("DEPARTMENT", user.getDepartment());
                    intent.putExtra("CLASS", user.getClassName());
                    startActivity(intent);
                    finish();
                } else {
                    Toast.makeText(LoginActivity.this, "用户不存在，请先注册", Toast.LENGTH_SHORT).show();
                }
            }
        });

        buttonRegister.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startActivity(new Intent(LoginActivity.this, RegisterActivity.class));
            }
        });
    }

    @Override
    protected void onDestroy() {
        dbHelper.close();
        super.onDestroy();
    }
}