错误提示是空指针异常，尝试调用接口，如果在成员变量处重新实现接口是可以的，测试ServiceConnection无法连接

package com.example.bankservice;

import android.content.ComponentName;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.Bundle;
import android.os.IBinder;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;

import com.example.bankservice.actions.Interfaces.NormalAccount;

public class NormalActivity extends AppCompatActivity implements View.OnClickListener {

    private static final String TAG = NormalActivity.class.getName();
    private NormalConnection normalConnection;
    private boolean mBind;
    private NormalAccount normalAccount;
    private Button bt_no1;
    private Button bt_no2;
    private Button bt_no3;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_normal);
        dobindService();
        initView();
    }

    private void dobindService() {
        Intent intent = new Intent();
        Log.d(TAG, "绑定服务");
        Toast.makeText(this, "绑定服务", Toast.LENGTH_SHORT).show();
        intent.setAction("com.example.bankserive.ACTION_NORMAL_USER");
        intent.addCategory(Intent.CATEGORY_DEFAULT);
        intent.setPackage("com.example.bankservice");
        normalConnection = new NormalConnection();
        mBind = bindService(intent, normalConnection, BIND_AUTO_CREATE);
    }

    private void initView() {
        bt_no1 = findViewById(R.id.bt_no1);
        bt_no2 = findViewById(R.id.bt_no2);
        bt_no3 = findViewById(R.id.bt_no3);

        bt_no1.setOnClickListener(this);
        bt_no2.setOnClickListener(this);
        bt_no3.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.bt_no1:
                Log.d(TAG, bt_no1.getText().toString());
                normalAccount.saveMoney(10000);//这几句错误
                break;
            case R.id.bt_no2:
                Log.d(TAG, bt_no2.getText().toString());
                normalAccount.getMoney();//这几句错误
                break;
            case R.id.bt_no3:
                Log.d(TAG, bt_no3.getText().toString());
                normalAccount.loan();//这几句错误
                break;
        }
    }

    private class NormalConnection implements ServiceConnection {

        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            Log.d(TAG, "连接服务：" + name);
//此处尝试，无法打印信息
            Toast.makeText(NormalActivity.this, "的顶顶顶顶顶的", Toast.LENGTH_SHORT).show();
            normalAccount = (NormalAccount) service;
            normalAccount.saveMoney(1000);
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {
            Log.d(TAG, "断开服务：" + name);
        }
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        if (mBind && normalConnection != null) {
            unbindService(normalConnection);
            Log.d(TAG, "解绑服务");
            normalConnection = null;
            mBind = false;
        }
    }
}