Conflito entre a content e activity main

Se eu uso o setContentView(R.layout.activity_main); quando o app roda me mostra a toolbar mas não consigo manipular os campos que estão na content main, mas uso o seetContentView(R.layout.content_main); eu consigo atualizar os campos, mas a toolbar some, como poderia resolver isso?

public class MainActivity extends AppCompatActivity {

    int contador;
    boolean podeSwipe = true;

    ImageView photoImageViewBotton;
    ImageView photoImageViewTop;
    TextView nameTextbox;
    EditText descriptionTextbox;
    ConstraintLayout mainLayout;


    int[] listaImagens = {R.drawable.sheldon01, R.drawable.sheldon02, R.drawable.sheldon03, R.drawable.sheldon04, R.drawable.sheldon05};

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // Apontando o layout
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        View nameView = findViewById(R.id.nameTextbox);

        nameView.findViewById(R.id.nameTextbox);


        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        photoImageViewTop = (ImageView) findViewById(R.id.photoImageViewTop);
        photoImageViewBotton = (ImageView) findViewById(R.id.photoImageViewBotton);
        nameTextbox = (TextView) findViewById(R.id.nameTextbox);
        descriptionTextbox = (EditText) findViewById(R.id.descriptionTextbox);
        mainLayout = (ConstraintLayout) findViewById(R.id.mainLayout);

        nameTextbox.setText("Sheldon");
        descriptionTextbox.setTag(descriptionTextbox.getKeyListener());
        descriptionTextbox.setKeyListener(null);
        descriptionTextbox.setText("123456789" +
                "sdfsdfsdfs\n" +
                "sdfsdfsdfs\n" +
                "sdfsdfsdfs\n" +
                "sdfsdfsdfs\n" +
                "sdfsdfsdfs\n" +
                "sdfsdfsdfs\n" +"sdfsdfsdfs\n" +"sdfsdfsdfs\n" +"sdfsdfsdfs\n" +"sdfsdfsdfs\n" +"sdfsdfsdfs\n" +
                "dfsdfsdfsdfdsf\n" +"dfsdfsdfsdfdsf\n" +"dfsdfsdfsdfdsf\n" +"dfsdfsdfsdfdsf\n" +"dfsdfsdfsdfdsf\n" +"dfsdfsdfsdfdsf\n" +
                "dfsdfsdfsdfsdfsdfsdfsdf\n");

        photoImageViewBotton.setImageResource(R.drawable.sheldon02);
        photoImageViewTop.setImageResource(R.drawable.sheldon01);

        photoImageViewBotton.setAlpha(0.0f);
        photoImageViewBotton.setRotation(-30.0f);
        photoImageViewBotton.setScaleX(0.35f);
        photoImageViewBotton.setScaleY(0.35f);

        photoImageViewTop.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                changePhoto();
            }
        });

    }
    }

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