如何在android studio上导入带id的浓缩咖啡?

我正试图用espresso为我的应用程序编写一个单元测试,但是每当我试图用id时,都找不到它。我该怎么解决?

这是我的代码:

package com.example.webowner.authenticate;

import android.content.Context;
import android.content.Intent;
import android.support.test.InstrumentationRegistry;
import android.support.test.espresso.Espresso;
import android.support.test.rule.ActivityTestRule;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ProgressBar;

import static android.support.test.espresso.Espresso.onView;
import static android.support.test.espresso.Espresso.;


import org.junit.After;
import org.junit.Before;
import org.junit.Rule;
import org.junit.Test;

import static org.junit.Assert.*;

public class MainActivityTest {

    @Rule
    public ActivityTestRule<MainActivity> mainActivityActivityTestRule = new ActivityTestRule<MainActivity>(MainActivity.class);

    @Test
    public void testLoginButton_shouldBeDisplayed()
    {
        //
    }

    @Before
    public void setUp() throws Exception {
    }

    @After
    public void tearDown() throws Exception {
    }
}