在注册活动中添加轮播选择器

Question

我正在尝试在注册时为头像添加轮播。我正在使用CarouselPicker库。我已经在一个独立的项目中尝试过该代码，并且效果很好。但是，当我尝试在我的工作项目（注册）中使用该库时，出现NullPointerExeption错误。我在做什么错了？

我的主要活动

import android.content.DialogInterface;
import android.content.Intent;
import android.support.annotation.NonNull;

import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;
import com.rengwuxian.materialedittext.MaterialEditText;


import java.util.ArrayList;
import java.util.List;

import eu.healthydev.quizhero.Common.Common;
import eu.healthydev.quizhero.Model.User;
import in.goodiebag.carouselpicker.CarouselPicker;


public class MainActivity extends AppCompatActivity {

    MaterialEditText edtNewUser ,edtNewPassword, edtNewEmail;  //For Sign up
    MaterialEditText edtUser, edtPassword;  //For Sign In
    CarouselPicker carouselPicker; // For Avatar

    Button btnSignUp, btnSignIn;
    FirebaseDatabase database;
    DatabaseReference users;



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

        //Firebase
        database = FirebaseDatabase.getInstance();
        users = database.getReference("Users");

        edtUser = (MaterialEditText) findViewById(R.id.edtUser);
        edtPassword =(MaterialEditText)findViewById(R.id.edtPassword);

        btnSignIn = (Button) findViewById(R.id.btn_sign_in);
        btnSignUp = (Button) findViewById(R.id.btn_sign_up);






        btnSignUp.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                showSignupDialog();
            }
        });

        btnSignIn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                signIn(edtUser.getText().toString(), edtPassword.getText().toString());
            }
        });

    }

    private void signIn(final String user, final String pwd) {
        users.addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                if (dataSnapshot.child(user).exists()){
                    if(!user.isEmpty()){
                        User login = dataSnapshot.child(user).getValue(User.class);
                        if(login.getPassword().equals(pwd)) {
                            Intent homeActivity = new Intent(MainActivity.this, HomeActivity.class);
                            Common.currentUser = login;
                            startActivity(homeActivity);
                            finish();
                        } else
                            Toast.makeText(MainActivity.this, "Wrong Password! ", Toast.LENGTH_SHORT).show();
                    }
                    else{
                        Toast.makeText(MainActivity.this, "Please enter your user name! ", Toast.LENGTH_SHORT).show();
                    }
                }
                else
                    Toast.makeText(MainActivity.this, "User is not exists! ", Toast.LENGTH_SHORT).show();

            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {

            }
        });
    }

    private void showSignupDialog() {

        AlertDialog.Builder alertDialog =new AlertDialog.Builder(MainActivity.this);
        alertDialog.setTitle("Sign Up");
        alertDialog.setMessage("Please full fill information");



        LayoutInflater inflater = this.getLayoutInflater();
        View sign_up_layout= inflater.inflate(R.layout.signup_layout, null);

        edtNewUser = (MaterialEditText) sign_up_layout.findViewById(R.id.edtNewUserName);
        edtNewEmail = (MaterialEditText) sign_up_layout.findViewById(R.id.edtNewEmail);
        edtNewPassword = (MaterialEditText) sign_up_layout.findViewById(R.id.edtNewPassword);
        carouselPicker = (CarouselPicker)findViewById(R.id.carouselPicker);

        alertDialog.setView(sign_up_layout);
        alertDialog.setIcon(R.drawable.ic_account_circle_black_24dp);

        //Carousel with images
        List<CarouselPicker.PickerItem> itemImages = new ArrayList<>();
        itemImages.add(new CarouselPicker.DrawableItem(R.mipmap.ic_launcher));
        itemImages.add(new CarouselPicker.DrawableItem(R.mipmap.ic_launcher_round));
        itemImages.add(new CarouselPicker.DrawableItem(R.mipmap.ic_launcher));
        itemImages.add(new CarouselPicker.DrawableItem(R.mipmap.ic_launcher));
        itemImages.add(new CarouselPicker.DrawableItem(R.mipmap.ic_launcher_round));
        itemImages.add(new CarouselPicker.DrawableItem(R.mipmap.ic_launcher));
        itemImages.add(new CarouselPicker.DrawableItem(R.mipmap.ic_launcher_round));


        CarouselPicker.CarouselViewAdapter imageAdapter = new CarouselPicker.CarouselViewAdapter(this,itemImages,0);
        carouselPicker.setAdapter(imageAdapter);

        alertDialog.setNegativeButton("NO", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialogInterface, int i) {
                dialogInterface.dismiss();

            }
        });

        alertDialog.setPositiveButton("YES", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialogInterface, int i) {
                final User user = new User(edtNewUser.getText().toString(),
                      edtNewPassword.getText().toString(),
                      edtNewEmail.getText().toString());

                users.addListenerForSingleValueEvent(new ValueEventListener() {
                    @Override
                    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                        if(dataSnapshot.child(user.getUserName()).exists())
                            Toast.makeText(MainActivity.this, "User already exists! ", Toast.LENGTH_SHORT).show();
                        else {
                            users.child(user.getUserName())
                                    .setValue(user);
                            Toast.makeText(MainActivity.this, "User registration success! ", Toast.LENGTH_SHORT).show();

                        }
                    }

                    @Override
                    public void onCancelled(@NonNull DatabaseError databaseError) {

                    }
                });
                dialogInterface.dismiss();

            }
        });
        alertDialog.show();

    }
}

我的Signup.xml

<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    app:cardElevation="4dp"
    android:background="@drawable/dungeon"
    android:layout_margin="8dp"
    >



    <LinearLayout
        android:layout_marginTop="60dp"
        android:orientation="vertical"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <in.goodiebag.carouselpicker.CarouselPicker
            android:layout_marginTop="20dp"
            android:layout_marginBottom="20dp"
            android:background="#DDD"
            android:id="@+id/carouselPicker"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:items_visible="seven">

        </in.goodiebag.carouselpicker.CarouselPicker>



        <com.rengwuxian.materialedittext.MaterialEditText

            android:id="@+id/edtNewUserName"
            android:hint="User Name"
            android:textColorHint="@color/colorPrimary"
            android:textColor="@color/colorPrimary"
            android:textSize="24dp"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:met_baseColor="@color/colorPrimary"
            android:fontFamily="@font/alagard"
            app:met_floatingLabel="highlight"
            app:met_primaryColor="@color/colorPrimary"
            app:met_singleLineEllipsis="true"/>

        <com.rengwuxian.materialedittext.MaterialEditText

            android:id="@+id/edtNewPassword"
            android:hint="Password"
            android:textColorHint="@color/colorPrimary"
            android:textColor="@color/colorPrimary"
            android:textSize="24dp"
            android:inputType="textPassword"
            android:fontFamily="@font/alagard"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:met_baseColor="@color/colorPrimary"
            app:met_floatingLabel="highlight"
            app:met_primaryColor="@color/colorPrimary"
            app:met_singleLineEllipsis="true"/>

        <com.rengwuxian.materialedittext.MaterialEditText

            android:id="@+id/edtNewEmail"
            android:hint="Email"
            android:textColorHint="@color/colorPrimary"
            android:textColor="@color/colorPrimary"
            android:textSize="24dp"
            android:inputType="textEmailAddress"
            android:fontFamily="@font/alagard"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:met_baseColor="@color/colorPrimary"
            app:met_floatingLabel="highlight"
            app:met_primaryColor="@color/colorPrimary"
            app:met_singleLineEllipsis="true"/>



    </LinearLayout>


</android.support.v7.widget.CardView>

和logcat

7-09 23:57:51.303 2768-2768/eu.healthydev.quizhero E/AndroidRuntime: FATAL EXCEPTION: main
    Process: eu.healthydev.quizhero, PID: 2768
    java.lang.NullPointerException
        at eu.healthydev.quizhero.MainActivity.showSignupDialog(MainActivity.java:142)
        at eu.healthydev.quizhero.MainActivity.access$000(MainActivity.java:31)
        at eu.healthydev.quizhero.MainActivity$1.onClick(MainActivity.java:67)
        at android.view.View.performClick(View.java:4438)
        at android.view.View$PerformClick.run(View.java:18422)
        at android.os.Handler.handleCallback(Handler.java:733)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:136)
        at android.app.ActivityThread.main(ActivityThread.java:5001)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
        at dalvik.system.NativeStart.main(Native Method)