我的“忘记密码”功能中是否缺少某些内容？

Question

对于我的Android应用，我有一个“忘记密码”按钮。在我的MainActivity.java中，该代码可以很好地单击“忘记密码？”。并将用户转移到一个名为ForgetPassword.java的新Java活动中（我遵循Mazn在线教程）。然后，我继续输入我的电子邮件（已经注册），然后单击“提交”以提交忘记密码的电子邮件。这只会使我回到MainActivity.java，但是，我不相信我在Password.java函数中的任何地方都可以调用它。

这是我的Password.java函数： 打包com.example.myapplication;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.util.Patterns;
import android.view.View;
import android.widget.EditText;
import android.widget.Button;
import android.widget.ProgressBar;


import android.os.Bundle;
import android.widget.Toast;

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

public class ForgotPassword extends AppCompatActivity {

    private EditText emailEt;
    private Button resetBtn;
    private ProgressBar progressbar;

    FirebaseAuth auth;



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

        progressbar = findViewById(R.id.progressBar4);
        auth = FirebaseAuth.getInstance();
        emailEt = findViewById(R.id.etEmail);
        resetBtn = findViewById(R.id.btnReset);
        resetBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String email = emailEt.getText().toString().trim();

                progressbar.setVisibility(View.VISIBLE);
                auth.sendPasswordResetEmail(email).addOnCompleteListener(new OnCompleteListener<Void>() {
                    @Override
                    public void onComplete(@NonNull Task<Void> task) {
                        if (task.isSuccessful())
                        {
                            Toast.makeText(getApplicationContext(), "Check your email to reset your password.", Toast.LENGTH_LONG).show();
                        }

                        else
                        {
                            Toast.makeText(getApplicationContext(), "Try again. Something went wrong!", Toast.LENGTH_LONG).show();
                        }
                    }
                });
            }
        });
        
    }

}

activity_forgot_password.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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=".ForgotPassword">

    <TextView
        android:id="@+id/tvPetWatch"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="28dp"
        android:fontFamily="sans-serif-black"
        android:gravity="center_horizontal"
        android:text="PetWatch"
        android:textAlignment="center"
        android:textSize="60sp"
        android:textStyle="bold"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/tvDescription"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="The app that watches your pet!"
        android:textStyle="italic"
        android:textSize="18sp"
        android:textAlignment="center"
        app:layout_constraintBottom_toTopOf="@+id/etEmail"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.497"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/tvPetWatch"
        app:layout_constraintVertical_bias="0.0"
        android:gravity="center_horizontal" />

    <EditText
        android:id="@+id/etEmailAddress"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="124dp"
        android:ems="10"
        android:hint="Enter email"
        android:inputType="textEmailAddress"
        android:textSize="24sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.496"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/tvDescription"
        app:layout_constraintVertical_bias="0.028" />

    <Button
        android:id="@+id/btnReset"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="12dp"
        android:text="Reset Password"
        android:textSize="24sp"
        app:backgroundTint="#3F51B5"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.497"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/etEmailAddress"
        app:layout_constraintVertical_bias="0.044" />

    <ProgressBar
        android:id="@+id/progressBar4"
        style="?android:attr/progressBarStyle"
        android:layout_width="wrap_content"
        android:visibility="invisible"
        android:layout_height="wrap_content"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.498"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/tvDescription"
        app:layout_constraintVertical_bias="0.316" />

</androidx.constraintlayout.widget.ConstraintLayout>

这是我的MainActivity.java函数：

package com.example.myapplication;

import androidx.annotation.NonNull;
import androidx.appcompat.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.TextView;
import android.widget.Toast;
import android.content.Intent;
import android.util.Log;

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

public class MainActivity extends AppCompatActivity {

    private EditText eEmail;
    private EditText ePassword;
    private Button eLogin;
    private TextView register;
    private ProgressBar progressBar;
    private TextView forgotPassword;

    boolean isValid = false;
    private int counter = 3;

    private FirebaseAuth mAuth;


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

        // Bind them to the XML layout

        // findViewById attaches the particular value to the particular XML element
        eEmail = findViewById(R.id.etEmail);
        ePassword = findViewById(R.id.etPassword);
        eLogin = findViewById(R.id.btnLogin);
        register = findViewById(R.id.tvRegister);
        FirebaseApp.initializeApp(MainActivity.this);
        mAuth = FirebaseAuth.getInstance();
        progressBar = findViewById(R.id.progressBar);
        forgotPassword = findViewById(R.id.tvForgotPassword);



        register.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                switch(v.getId())
                {
                    case R.id.tvRegister:
                        startActivity(new Intent(MainActivity.this, RegisterUser.class));
                        break;
                    default:
                        throw new IllegalStateException("Unexpected value: " + v.getId());
                }
            }




        });

        eLogin.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                switch(v.getId())
                {
                    case R.id.btnLogin:
                    {
                        userLogin();
                        break;
                    }
                }
            }
        });

        forgotPassword.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                switch(v.getId())
                {
                    case R.id.tvForgotPassword:
                        startActivity(new Intent(MainActivity.this, ForgotPassword.class));
                        break;
                    default:
                        throw new IllegalStateException("Unexpected value: " + v.getId());
                }
            }
        });

    }

    private void userLogin() {
        String email = eEmail.getText().toString().trim();
        String password = ePassword.getText().toString().trim();

        if (email.isEmpty())
        {
            eEmail.setError("Email is required!");
            eEmail.requestFocus();
            return;
        }

        if (!Patterns.EMAIL_ADDRESS.matcher(email).matches())
        {
            eEmail.setError("Please enter a valid email address!");
            eEmail.requestFocus();
            return;
        }

        if (password.isEmpty())
        {
            ePassword.setError("Email is required!");
            ePassword.requestFocus();
            return;
        }

        progressBar.setVisibility(View.VISIBLE);


        mAuth.signInWithEmailAndPassword(email, password).addOnCompleteListener(new OnCompleteListener<AuthResult>() {
            @Override
            public void onComplete(@NonNull Task<AuthResult> task) {
                if (task.isSuccessful())
                {
                    // direct to user profile
                    FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();


                    if (user.isEmailVerified())
                    {
                        startActivity(new Intent(MainActivity.this, ProfileActivity.class));
                        Toast.makeText(getApplicationContext(), "Login credentials was successful!", Toast.LENGTH_LONG).show();
                        progressBar.setVisibility(View.GONE);
                    }

                    else
                    {
                        user.sendEmailVerification();
                        Toast.makeText(getApplicationContext(), "Please check your email to verify your account.", Toast.LENGTH_LONG).show();
                        progressBar.setVisibility(View.GONE);

                    }
                }

                else
                {
                    Toast.makeText(getApplicationContext(), "Failed to login! Recheck your credentials.", Toast.LENGTH_LONG).show();
                    progressBar.setVisibility(View.GONE);
                }
            }
        });

    }

}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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=".MainActivity">

    <EditText
        android:id="@+id/etEmail"
        android:layout_width="380dp"
        android:layout_height="wrap_content"
        android:layout_marginTop="60dp"
        android:ems="10"
        android:hint="Enter email address"
        android:inputType="textEmailAddress"
        android:textSize="24sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.497"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.314" />

    <Button
        android:id="@+id/btnLogin"
        android:layout_width="380dp"
        android:layout_height="70dp"
        android:layout_marginTop="24dp"
        android:textStyle="bold"
        android:ems="10"
        android:text="Login"
        android:textSize="24sp"
        app:backgroundTint="#3F51B5"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.498"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/etPassword"
        app:layout_constraintVertical_bias="0.097" />

    <EditText
        android:id="@+id/etPassword"
        android:layout_width="380dp"
        android:layout_height="wrap_content"
        android:ems="10"
        android:hint="Enter password"
        android:inputType="textPassword"
        android:textSize="24sp"
        android:layout_marginTop="30dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.497"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/etEmail"
        app:layout_constraintVertical_bias="0.058" />

    <TextView
        android:id="@+id/tvPetWatch"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="28dp"
        android:fontFamily="sans-serif-black"
        android:gravity="center_horizontal"
        android:text="PetWatch"
        android:textAlignment="center"
        android:textSize="60sp"
        android:textStyle="bold"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/tvDescription"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="The app that watches your pet!"
        android:textStyle="italic"
        android:textSize="18sp"
        android:textAlignment="center"
        app:layout_constraintBottom_toTopOf="@+id/etEmail"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.497"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/tvPetWatch"
        app:layout_constraintVertical_bias="0.0"
        android:gravity="center_horizontal" />

    <TextView
        android:id="@+id/tvForgotPassword"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Forgot Password?"
        android:textSize="16sp"
        android:textStyle="bold"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.056"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/btnLogin"
        app:layout_constraintVertical_bias="0.096" />

    <TextView
        android:id="@+id/tvRegister"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="New User? Register Here!"
        android:textSize="16sp"
        android:textStyle="bold"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.94"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/btnLogin"
        app:layout_constraintVertical_bias="0.095" />

    <ProgressBar
        android:id="@+id/progressBar"
        style="?android:attr/progressBarStyleLarge"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:visibility="invisible"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

Answer 1

您的emailEt在MainActivity中，因此在ForgotPassword Activity中调用findViewByID(R.id.etEmail)会返回空引用。

当我单击“重置”按钮时，它似乎在移动MainActivity，但实际上，该应用程序崩溃了。

我的本​​地日志：

2020-11-12 15:44:38.964 7425-7425/xyz.dps0340.myapplication E/AndroidRuntime: FATAL EXCEPTION: main
    Process: xyz.dps0340.myapplication, PID: 7425
    java.lang.NullPointerException: Attempt to invoke virtual method 'android.text.Editable android.widget.EditText.getText()' on a null object reference
        at xyz.dps0340.myapplication.ForgotPassword$1.onClick(ForgotPassword.java:43)
        at android.view.View.performClick(View.java:7448)
        at com.google.android.material.button.MaterialButton.performClick(MaterialButton.java:992)
        at android.view.View.performClickInternal(View.java:7425)
        at android.view.View.access$3600(View.java:810)
        at android.view.View$PerformClick.run(View.java:28305)
        at android.os.Handler.handleCallback(Handler.java:938)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:223)
        at android.app.ActivityThread.main(ActivityThread.java:7656)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)

您必须在ForgotPassword活动中使用etEmailAddress视图。

代码：

Xml文件相同。

MainActivity.java

package com.example.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Context;
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.TextView;
import android.content.Intent;

import com.google.firebase.FirebaseApp;
import com.google.firebase.auth.FirebaseAuth;

public class MainActivity extends AppCompatActivity {

    private EditText eEmail;
    private EditText ePassword;
    private Button eLogin;
    private TextView register;
    private ProgressBar progressBar;
    private TextView forgotPassword;

    boolean isValid = false;
    private int counter = 3;

    private FirebaseAuth mAuth;


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

        // Bind them to the XML layout

        // findViewById attaches the particular value to the particular XML element
        eEmail = findViewById(R.id.etEmail);
        ePassword = findViewById(R.id.etPassword);
        eLogin = findViewById(R.id.btnLogin);
        register = findViewById(R.id.tvRegister);
        FirebaseApp.initializeApp(getApplicationContext());
        mAuth = FirebaseAuth.getInstance();
        progressBar = findViewById(R.id.progressBar);
        forgotPassword = findViewById(R.id.tvForgotPassword);



        register.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                switch(v.getId())
                {
                    case R.id.tvRegister:
                        startActivity(new Intent(MainActivity.this, RegisterUser.class));
                        break;
                    default:
                        throw new IllegalStateException("Unexpected value: " + v.getId());
                }
            }




        });

        eLogin.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                switch(v.getId())
                {
                    case R.id.btnLogin:
                    {
                        userLogin();
                        break;
                    }
                }
            }
        });

        forgotPassword.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                switch(v.getId())
                {
                    case R.id.tvForgotPassword:
                        Intent forgotPasswordIntent = new Intent(MainActivity.this, ForgotPassword.class);
                        startActivity(forgotPasswordIntent);
                        break;
                    default:
                        throw new IllegalStateException("Unexpected value: " + v.getId());
                }
            }
        });

    }

    private void userLogin() {
        String email = eEmail.getText().toString().trim();
        String password = ePassword.getText().toString().trim();

        if (email.isEmpty())
        {
            eEmail.setError("Email is required!");
            eEmail.requestFocus();
            return;
        }

        if (!Patterns.EMAIL_ADDRESS.matcher(email).matches())
        {
            eEmail.setError("Please enter a valid email address!");
            eEmail.requestFocus();
            return;
        }

        if (password.isEmpty())
        {
            ePassword.setError("Email is required!");
            ePassword.requestFocus();
            return;
        }

        progressBar.setVisibility(View.VISIBLE);


        mAuth.signInWithEmailAndPassword(email, password).addOnCompleteListener(new OnCompleteListener<AuthResult>() {
            @Override
            public void onComplete(@NonNull Task<AuthResult> task) {
                if (task.isSuccessful())
                {
                    // direct to user profile
                    FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();


                    if (user.isEmailVerified())
                    {
                        startActivity(new Intent(MainActivity.this, ProfileActivity.class));
                        Toast.makeText(getApplicationContext(), "Login credentials was successful!", Toast.LENGTH_LONG).show();
                        progressBar.setVisibility(View.GONE);
                    }

                    else
                    {
                        user.sendEmailVerification();
                        Toast.makeText(getApplicationContext(), "Please check your email to verify your account.", Toast.LENGTH_LONG).show();
                        progressBar.setVisibility(View.GONE);

                    }
                }

                else
                {
                    Toast.makeText(getApplicationContext(), "Failed to login! Recheck your credentials.", Toast.LENGTH_LONG).show();
                    progressBar.setVisibility(View.GONE);
                }
            }
        });

    }

}

ForgotPassword.java

package com.example.myapplication;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.util.Patterns;
import android.view.View;
import android.widget.EditText;
import android.widget.Button;
import android.widget.ProgressBar;


import android.os.Bundle;
import android.widget.Toast;

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

public class ForgotPassword extends AppCompatActivity {

    private Button resetBtn;
    private ProgressBar progressbar;
    private EditText emailAddress;

    FirebaseAuth auth;



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

        Intent intent = getIntent();
        emailAddress = findViewById(R.id.etEmailAddress);
        progressbar = findViewById(R.id.progressBar4);
        auth = FirebaseAuth.getInstance();
        resetBtn = findViewById(R.id.btnReset);
        resetBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String email = emailAddress.getText().toString();
                if(email.equals("")) {
                    Toast.makeText(getApplicationContext(), "Your Email is wrong.", Toast.LENGTH_LONG).show();
                    return;
                }
                progressbar.setVisibility(View.VISIBLE);
                auth.sendPasswordResetEmail(email).addOnCompleteListener(new OnCompleteListener<Void>() {
                    @Override
                    public void onComplete(@NonNull Task<Void> task) {
                        if (task.isSuccessful())
                        {
                            Toast.makeText(getApplicationContext(), "Check your email to reset your password.", Toast.LENGTH_LONG).show();
                        }

                        else
                        {
                            Toast.makeText(getApplicationContext(), "Try again. Something went wrong!", Toast.LENGTH_LONG).show();
                        }
                        progressbar.setVisibility(View.INVISIBLE);
                    }
                });
            }
        });

    }

}