android 学习

今天写了登录界面

package com.example.myapplication2;

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

import androidx.appcompat.app.AppCompatActivity;

public class Firstactivity extends AppCompatActivity implements View.OnClickListener{
    private EditText editText21;
    private DatabaseHelper2 dbHelper;
    private int p=1;
    String k="";
    String xuehao="";
    String phone="";
    String cla="";


    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_first);
        editText21 = (EditText) findViewById(R.id.edit_21);

        initUI3();
    }

    private void initUI3() {
        findViewById(R.id.button1).setOnClickListener(this);
        findViewById(R.id.button2).setOnClickListener(this);
        findViewById(R.id.button).setOnClickListener(this);
    }
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.button1://执行按钮1
                String mm=editText21.getText().toString();
                dbHelper=new DatabaseHelper2(this,"TTList2.db",null,3);
                SQLiteDatabase db=dbHelper.getWritableDatabase();
                Cursor cursor=db.query("TTList2",null,null,null,
                        null,null,null);//读取数据库里面专业是软件工程的所有信息
                if(cursor.moveToFirst()){
                    do{
                        String ye=cursor.getString(cursor.getColumnIndex("手机号"));
                        Log.d("Firstactivity","手机号："+ye);
                        Log.d("Firstactivity","手机号："+mm);
                        if(ye.equals(mm))
                        {
                            k=cursor.getString(cursor.getColumnIndex("姓名"));
                            xuehao=cursor.getString(cursor.getColumnIndex("学号"));
                            phone=cursor.getString(cursor.getColumnIndex("手机号"));
                            cla=cursor.getString(cursor.getColumnIndex("班级"));
                            p=2;
                        }

                    }while (cursor.moveToNext());
                }
                cursor.close();
                if(p==2) {
                    Intent intent = new Intent();
                    intent.putExtra("name",k);
                    intent.putExtra("xuehao",xuehao);
                    intent.putExtra("phone",phone);
                    intent.putExtra("cla",cla);
                    intent.setClass(getApplicationContext(), MainActivity.class);
                    this.startActivity(intent);
                    p=1;
                }
                else
                {
                    Toast.makeText(Firstactivity.this, "无该用户信息", Toast.LENGTH_SHORT).show();
                }
                break;
            case R.id.button2:
                Intent intent2 = new Intent();
                intent2.setClass(getApplicationContext(), zhuce.class);
                this.startActivity(intent2);
                break;


            case R.id.button:
                Intent intent3 = new Intent();

                intent3.setClass(getApplicationContext(), chakan.class);
                this.startActivity(intent3);
                break;



        }
    }
}