每当我尝试更改活动时，我的应用都会崩溃

Question

我正在使用firebase身份验证和实时数据库。我的textViewSingup工作完全正常交换活动，直到我添加了实时数据库，之后每当我点击更改活动时它都会崩溃我的应用程序。在几次尝试修复之后，我添加了一个按钮，看看是否可以解决这个问题，但它完全相同。

这是我的代码。

主要活动代码

import android.content.Intent;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Patterns;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ProgressBar;
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 MainActivity extends AppCompatActivity implements View.OnClickListener{

    EditText editTextEmail, editTextPassword;
    ProgressBar progressBar;

    private Button button;


    FirebaseAuth mAuth;

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

        mAuth = FirebaseAuth.getInstance();

        editTextEmail = findViewById(R.id.editTextEmail);
        editTextPassword = findViewById(R.id.editTextPassword);
        progressBar = findViewById(R.id.progressBar);

        findViewById(R.id.textViewSignup).setOnClickListener(this);
        findViewById(R.id.buttonLogin).setOnClickListener(this);

        button = (Button) findViewById(R.id.buttonRegister);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                openRegistration();
            }
        });

    }

    public void openRegistration(){
        Intent intent = new Intent(this, SignUpActivity.class);
        startActivity(intent);
    }

    private void userLogin(){

        String email = editTextEmail.getText().toString().trim();
        String password = editTextPassword.getText().toString().trim();

        if(email.isEmpty()){
            editTextEmail.setError("Please provide your Email");
            editTextEmail.requestFocus();
            return;
        }

        if(!Patterns.EMAIL_ADDRESS.matcher(email).matches()){
            editTextPassword.setError("Please Enter a Valid Email Address");
            editTextPassword.requestFocus();
            return;
        }

        if(password.length()<6){
            editTextPassword.setError("Password is Incorrect");
            editTextPassword.requestFocus();
            return;
        }

        if(password.isEmpty()){
            editTextPassword.setError("Please provide your Password");
            editTextPassword.requestFocus();
            return;
        }

        progressBar.setVisibility(View.VISIBLE);


        mAuth.signInWithEmailAndPassword(email, password).addOnCompleteListener(new OnCompleteListener<AuthResult>() {
            @Override
            public void onComplete(@NonNull Task<AuthResult> task) {
                progressBar.setVisibility(View.GONE);
                if(task.isSuccessful()){
                    Intent intent = new Intent(MainActivity.this, ProfileActivity.class);
                    intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                    startActivity(intent);

                }else{
                    Toast.makeText(getApplicationContext(), task.getException().getMessage(), Toast.LENGTH_SHORT).show();
                }
            }
        });

    }

    @Override
    public void onClick(View view) {

        switch (view.getId()){

            case R.id.textViewSignup:

                startActivity(new Intent(this, SignUpActivity.class));
                break;

            case R.id.buttonLogin:
                userLogin();
                break;
        }

    }
}

MainActivity.xml代码

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="ie.wit.ca2.MainActivity">

    <EditText
        android:id="@+id/editTextPassword"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:ems="10"
        android:hint="Password"
        android:inputType="textPassword"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.503"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.374" />

    <Button
        android:id="@+id/buttonLogin"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:text="Login"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.63" />

    <TextView
        android:id="@+id/textViewSignup"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:text="Create an account here"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.502"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.869" />

    <EditText
        android:id="@+id/editTextEmail"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:ems="10"
        android:hint="Email Address"
        android:inputType="textEmailAddress"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.503"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.233" />

    <ProgressBar
        android:id="@+id/progressBar"
        style="?android:attr/progressBarStyle"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:visibility="gone"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.501"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.477" />

    <Button
        android:id="@+id/buttonRegister"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:text="Register"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/buttonLogin"
        app:layout_constraintVertical_bias="0.055" />
</android.support.constraint.ConstraintLayout>

SignupActivity代码

import android.content.Intent;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Patterns;
import android.view.View;
import android.widget.EditText;
import android.widget.ProgressBar;
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;
import com.google.firebase.auth.FirebaseAuthUserCollisionException;

public class SignUpActivity extends AppCompatActivity implements View.OnClickListener{

    ProgressBar progressBar;

    EditText editTextEmail, editTextPassword;

    private FirebaseAuth mAuth;



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

        editTextEmail = findViewById(R.id.editTextEmail);
        editTextPassword = findViewById(R.id.editTextPassword);
        progressBar = findViewById(R.id.progressBar);

        mAuth = FirebaseAuth.getInstance();

        findViewById(R.id.buttonSignUp).setOnClickListener(this);
        findViewById(R.id.textViewSignup).setOnClickListener(this);


    }

    private void registerUser(){
        String email = editTextEmail.getText().toString().trim();
        String password = editTextPassword.getText().toString().trim();

        if(email.isEmpty()){
            editTextEmail.setError("Please provide your Email");
            editTextEmail.requestFocus();
            return;
        }

        if(!Patterns.EMAIL_ADDRESS.matcher(email).matches()){
            editTextPassword.setError("Please Enter a Valid Email Address");
            editTextPassword.requestFocus();
            return;
        }

        if(password.length()<6){
            editTextPassword.setError("Password must have minimum 6 characters");
            editTextPassword.requestFocus();
            return;
        }

        if(password.isEmpty()){
            editTextPassword.setError("Please provide your Password");
            editTextPassword.requestFocus();
            return;
        }

        progressBar.setVisibility(View.VISIBLE);

        mAuth.createUserWithEmailAndPassword(email, password).addOnCompleteListener(new OnCompleteListener<AuthResult>() {
            @Override
            public void onComplete(@NonNull Task<AuthResult> task) {
                progressBar.setVisibility(View.GONE);
                if(task.isSuccessful()){

                    Intent intent = new Intent(SignUpActivity.this, ProfileActivity.class);
                    intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                    startActivity(intent);

                }else{

                    if(task.getException() instanceof FirebaseAuthUserCollisionException){
                        Toast.makeText(getApplicationContext(), "This Email has already been registered", Toast.LENGTH_SHORT).show();
                    }else {
                        Toast.makeText(getApplicationContext(), task.getException().getMessage(), Toast.LENGTH_SHORT).show();
                    }

                }
            }
        });
    }

    @Override
    public void onClick(View view) {
        switch (view.getId()){
            case R.id.buttonSignUp:
                registerUser();

                break;

            case R.id.textViewLogin:

                startActivity(new Intent(this, MainActivity.class));
                break;

        }

    }
}

这是我在尝试更改活动时遇到的错误。

04-29 11:41:04.775 12204-12204/ie.wit.ca2 E/AndroidRuntime: FATAL EXCEPTION: main
    Process: ie.wit.ca2, PID: 12204
    java.lang.RuntimeException: Unable to start activity ComponentInfo{ie.wit.ca2/ie.wit.ca2.SignUpActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.View.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2778)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856)
        at android.app.ActivityThread.-wrap11(Unknown Source:0)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6494)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.View.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
        at ie.wit.ca2.SignUpActivity.onCreate(SignUpActivity.java:41)
        at android.app.Activity.performCreate(Activity.java:7009)
        at android.app.Activity.performCreate(Activity.java:7000)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1214)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2731)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856) 
        at android.app.ActivityThread.-wrap11(Unknown Source:0) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loop(Looper.java:164) 
        at android.app.ActivityThread.main(ActivityThread.java:6494) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807) 

Answer 1

因此，经过几个小时试图找到问题，我终于注意到了什么是错的。在我的注册活动的第41行中，我正在调用一个不存在的文本视图，从而使我的应用程序始终崩溃。