安卓选课系统源码（基于sqlite数据库）

Android Studio开发的选课系统，功能主要有有以下几项：学生注册；管理员、学生登录；学生选课信息管理（增删改查）；管理员管理课程信息（增删改查）。

package com.example.student;
/**
 * 登录主界面
 */
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import com.example.dao.UserService;
import com.example.guanli.Gl;
public class MainActivity extends Activity {
   // 分别为用户名和密码
   private EditText mUsername;
   private EditText mPassword;
   // 分别为登陆和注册按钮
   private Button mLogin;
   private Button mRegister;
   private Button a;
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      mUsername = (EditText) findViewById(R.id.username);
      mPassword = (EditText) findViewById(R.id.password);
      mLogin = (Button) findViewById(R.id.button1);
      mRegister = (Button) findViewById(R.id.button2);
      a = (Button) findViewById(R.id.button4);
      // 登陆
      mLogin.setOnClickListener(new OnClickListener() {
         @Override
         public void onClick(View arg0) {
            String userName = mUsername.getText().toString().trim();
            String passWord = mPassword.getText().toString().trim();
            UserService userService = new UserService(MainActivity.this);
            if (mUsername.getText().toString().trim().equals(""))  {
               Toast.makeText(getApplicationContext(), "用户名不能为空！",
                     Toast.LENGTH_SHORT).show();
               return;
            }
            if (mPassword.getText().toString().equals("")) {
               Toast.makeText(getApplicationContext(), "密码不能为空！",
                     Toast.LENGTH_SHORT).show();
               return;
            }
            boolean flag = userService.Login(userName, passWord);
            if (flag) {
               Toast.makeText(MainActivity.this, "登录成功！",
                     Toast.LENGTH_SHORT).show();
               Intent intent = new Intent();
               intent.setClass(MainActivity.this,
                     YhuMainActivity.class);
               startActivity(intent);
            } else {
               Toast.makeText(MainActivity.this, "登录失败！",
                     Toast.LENGTH_SHORT).show();
            }
         }
      });
      // 注册
      mRegister.setOnClickListener(new OnClickListener() {
         @Override
         public void onClick(View arg0) {
            Intent intent = new Intent();
            intent.setClass(MainActivity.this, RegisterActivity.class);
            startActivity(intent);
         }
      });
      //管理
      a.setOnClickListener(new OnClickListener() {
         @Override
         public void onClick(View arg0) {
            Intent intent = new Intent();
            intent.setClass(MainActivity.this, Gl.class);
            startActivity(intent);
         }
      });
   }
   @Override
   public boolean onCreateOptionsMenu(Menu menu) {
      // Inflate the menu; this adds items to the action bar if it is present.
      getMenuInflater().inflate(R.menu.main, menu);
      return true;
   }
}