Question

每当我尝试运行应用时，我都会收到错误消息：

这是.java类：

package com.safariagaming.flix;


import android.app.ProgressDialog;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.auth.AuthResult;
import com.google.firebase.auth.FirebaseAuth;

public class SignUpScreen extends AppCompatActivity implements View.OnClickListener{

    //defining view objects
    private EditText editTextEmail;
    private EditText editTextPassword;
    private Button buttonSignup;
    private ProgressDialog progressDialog;


    //defining firebaseauth object
    private FirebaseAuth firebaseAuth;

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

        //initializing firebase auth object
        firebaseAuth = FirebaseAuth.getInstance();


        //initializing views
        editTextEmail = (EditText) findViewById(R.id.editTextEmail);
        editTextPassword = (EditText) findViewById(R.id.editTextPassword);

        buttonSignup = (Button) findViewById(R.id.buttonSignup);

        progressDialog = new ProgressDialog(this);

        //attaching listener to button
        buttonSignup.setOnClickListener(this);
    }

    private void registerUser(){

        //getting email and password from edit texts
        String email = editTextEmail.getText().toString().trim();
        String password  = editTextPassword.getText().toString().trim();

        //checking if email and passwords are empty
        if(TextUtils.isEmpty(email)){
            Toast.makeText(this,"Please enter email",Toast.LENGTH_LONG).show();
            return;
        }

        if(TextUtils.isEmpty(password)){
            Toast.makeText(this,"Please enter password",Toast.LENGTH_LONG).show();
            return;
        }

        //if the email and password are not empty
        //displaying a progress dialog

        progressDialog.setMessage("Registering Please Wait...");

        //creating a new user
        firebaseAuth.createUserWithEmailAndPassword(email, password)
                .addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {
                        //checking if success
                        if(task.isSuccessful()){
                            //display some message here
                            Toast.makeText(SignUpScreen.this,"Successfully registered",Toast.LENGTH_LONG).show();
                        }else{
                            //display some message here
                            Toast.makeText(SignUpScreen.this,"Registration Error",Toast.LENGTH_LONG).show();
                        }
                        progressDialog.dismiss();
                    }
                });

    }

    @Override
    public void onClick(View view) {
        //calling register method on click
        registerUser();
    }
}

（我认为错误发生是因为我没有正确初始化firebase auth对象）

这是我的XML类

android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
>

<LinearLayout
    android:layout_centerVertical="true"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical">

    <EditText
        android:id="@+id/editTextEmail"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="15dp"
        android:hint="Enter email"
        android:inputType="textEmailAddress" />

    <EditText
        android:id="@+id/editTextPassword"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="15dp"
        android:hint="Enter password"
        android:inputType="textPassword" />

    <Button
        android:id="@+id/buttonSignup"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="15dp"
        android:text="Signup" />

</LinearLayout>

以下是我遇到的错误消息

03-29 18:14:49.700 9230-9230/com.safariagaming.flix E/AndroidRuntime: FATAL EXCEPTION: main
                                                                  Process: com.safariagaming.flix, PID: 9230
                                                                  java.lang.NullPointerException: Attempt to invoke virtual method 'com.google.android.gms.tasks.Task com.google.firebase.auth.FirebaseAuth.createUserWithEmailAndPassword(java.lang.String, java.lang.String)' on a null object reference
                                                                      at com.safariagaming.flix.SignUpScreen.registerUser(SignUpScreen.java:72)
                                                                      at com.safariagaming.flix.SignUpScreen.onClick(SignUpScreen.java:93)
                                                                      at android.view.View.performClick(View.java:5637)
                                                                      at android.view.View$PerformClick.run(View.java:22429)
                                                                      at android.os.Handler.handleCallback(Handler.java:751)
                                                                      at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                      at android.os.Looper.loop(Looper.java:154)
                                                                      at android.app.ActivityThread.main(ActivityThread.java:6119)
                                                                      at java.lang.reflect.Method.invoke(Native Method)
                                                                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
                                                                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)

Answer 1

您应该已经在方法email之外定义了变量password和registerUser() 。看来你的Button也没有正确设置。

package com.safariagaming.flix;

/**
 * Imports...
 */

public class SignUpScreen extends AppCompatActivity implements View.OnClickListener {

   private String email = null;
   private String password = null;
   private FirebaseAuth.AuthStateListener mAuthListener;

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

  /**
   * Inits and code...
   */

    // Signup button on listener
    buttonSignup.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        email = editTextEmail.getText().toString().trim();
        password = editTextPassword.getText().toString().trim();

        // Verifications
        if (TextUtils.isEmpty(email)) {
            Toast.makeText(LoginActivity.this, R.string.empty_email, Toast.LENGTH_SHORT).show();
            return;
        }

        if (!Patterns.EMAIL_ADDRESS.matcher(email).matches()) {
            Toast.makeText(LoginActivity.this, R.string.wrong_email, Toast.LENGTH_SHORT).show();
            return;
        }

        if (TextUtils.isEmpty(password)) {
            Toast.makeText(LoginActivity.this, R.string.empty_password, Toast.LENGTH_SHORT).show();
        }

        // Authenticating user
        mAuth.createUserWithEmailAndPassword(email, password)
                .addOnCompleteListener(LoginActivity.this, new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {


                        if (!task.isSuccessful()) {
                            Toast.makeText(LoginActivity.this, R.string.wrong_credentials, Toast.LENGTH_SHORT).show();
                        } else {
                            goDashboard();
                            finish();
                        }
                    }
                });
             }
         });
      }
   // onStart() state listener
   @Override
    public void onStart() {
        super.onStart();
        mAuth.addAuthStateListener(mAuthListener);
    }

    @Override
    public void onStop() {
        super.onStop();
        if (mAuthListener != null) {
             mAuth.removeAuthStateListener(mAuthListener);
        }
    }
 }

Answer 2

java.lang.NullPointerException：尝试调用虚方法 “com.google.android.gms.tasks.Task com.google.firebase.auth.FirebaseAuth.createUserWithEmailAndPassword（java.lang.String中， “空对象引用
上的java.lang.String）”

这意味着您的mAuth成员变量为null。您可能从未为其分配过值。在onCreate（）期间或至少在您调用createUserWithEmailAndPassword之前的某个时间为其分配mAuth = FirebaseAuth.getInstance()。

初始化Firebase auth对象错误

2 个答案: