AndroidStudio数据库连接有问题

package com.example.daka;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.EditText;

import com.example.daka.database.UserDBHelper;
import com.example.daka.enity.User;
import com.example.daka.util.ToastUtil;

public class ZuceActivity extends AppCompatActivity implements View.OnClickListener {

    private EditText et_name;
    private EditText et_phone;
    private EditText et_classroom;
    private EditText et_password;
    private EditText et_ID;
    private UserDBHelper mHelper;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_zuce);
        et_name=findViewById(R.id.et_name);
        et_phone=findViewById(R.id.et_phone);
        et_classroom=findViewById(R.id.et_classroom);
        et_password=findViewById(R.id.et_password);
        et_ID=findViewById(R.id.et_ID);
        findViewById(R.id.btn_zuce).setOnClickListener(this);
    }

    @Override
    protected void onStart() {
        super.onStart();
        mHelper =UserDBHelper.getInstance(this);
        //mHelper.openWriteLink();
        //mHelper.openReadLink();
    }

    @Override
    protected void onStop() {
        super.onStop();
        mHelper.closeLink();
    }

    @Override
    public void onClick(View v) {
        String ID=et_ID.getText().toString();
        String name=et_name.getText().toString();
        String password=et_password.getText().toString();
        String phone=et_phone.getText().toString();
        String classroom=et_classroom.getText().toString();
        User user=null;
        switch(v.getId()){
            case R.id.btn_zuce:
                user= new User(Integer.parseInt(ID),name,password,phone,classroom);
                mHelper.insert(user);
                if(mHelper.insert(user)>0){
                    ToastUtil.show(this,"注册成功");
                }
                break;
        }
    }
}