嗨，我是Android开发的新手，我在android应用程序中工作，我的应用程序包括注册和登录活动。因此，我正在进行注册活动，但是当我单击“注册”按钮时，应用程序停止工作。
我也知道这是由于NullPointerException引起的，但是我无法解决问题。
我收到的错误是应用程序意外停止了……希望我对大家说清楚。
SignupActivity.java
package com.example.kiit.shoppar;
import android.content.Intent;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
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;
import com.google.firebase.auth.FirebaseUser;
import com.google.firebase.auth.UserProfileChangeRequest;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import java.util.Calendar;
import java.util.HashMap;
import java.util.Locale;
public class SignupActivity extends AppCompatActivity {
Button reg;
EditText fname, lname, pass, inputEmail, phone;
FirebaseAuth auth;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_signup);
fname = (EditText) findViewById(R.id.txtfname);
lname = (EditText) findViewById(R.id.txtlname);
pass = (EditText) findViewById(R.id.txtpass);
inputEmail = (EditText) findViewById(R.id.txtemail);
phone = (EditText) findViewById(R.id.txtphone);
reg = (Button) findViewById(R.id.btnreg);
reg.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
final String firstName = fname.getText().toString().trim();
final String lastName = lname.getText().toString().trim();
final String email = inputEmail.getText().toString().trim();
final String password = pass.getText().toString().trim();
final String phoneno = phone.getText().toString().trim();
if (TextUtils.isEmpty(firstName)) {
Toast.makeText(getApplicationContext(), "Enter first name!", Toast.LENGTH_SHORT).show();
return;
}
if (TextUtils.isEmpty(lastName)) {
Toast.makeText(getApplicationContext(), "Enter last name!", Toast.LENGTH_SHORT).show();
return;
}
if (TextUtils.isEmpty(email)) {
Toast.makeText(getApplicationContext(), "Enter email address!", Toast.LENGTH_SHORT).show();
return;
}
if (TextUtils.isEmpty(password)) {
Toast.makeText(getApplicationContext(), "Enter password!", Toast.LENGTH_SHORT).show();
return;
}
if (TextUtils.isEmpty(phoneno)) {
Toast.makeText(getApplicationContext(), "Enter phone number!", Toast.LENGTH_SHORT).show();
return;
}
if (password.length() < 6) {
Toast.makeText(getApplicationContext(), "Password too short, enter minimum 6 characters!", Toast.LENGTH_SHORT).show();
return;
}
if (phoneno.length() < 10) {
Toast.makeText(getApplicationContext(), "Invalid Phone Number!", Toast.LENGTH_SHORT).show();
return;
}
//progressBar.setVisibility(View.VISIBLE);
//create user
auth.createUserWithEmailAndPassword(email, password)
.addOnCompleteListener(SignupActivity.this, new OnCompleteListener<AuthResult>() {
@Override
public void onComplete(@NonNull Task<AuthResult> task) {
Toast.makeText(SignupActivity.this, "createUserWithEmail:onComplete:" + task.isSuccessful(), Toast.LENGTH_SHORT).show();
//progressBar.setVisibility(View.GONE);
// If sign in fails, display a message to the user. If sign in succeeds
// the auth state listener will be notified and logic to handle the
// signed in user can be handled in the listener.
if (!task.isSuccessful()) {
Toast.makeText(SignupActivity.this, "Authentication failed." + task.getException(),
Toast.LENGTH_SHORT).show();
} else {
HashMap<String, Object> map = new HashMap<String, Object>();
final FirebaseUser user = task.getResult().getUser();
map.put("user_id", user.getUid());
map.put("email", email);
map.put("last_connection", Calendar.getInstance(Locale.US).getTimeInMillis());
DatabaseReference userDbRef = FirebaseDatabase.getInstance().getReference().child("user").child(user.getUid());
userDbRef.setValue(map)
.addOnCompleteListener(new OnCompleteListener<Void>() {
@Override
public void onComplete(@NonNull Task<Void> task) {
if (task.isSuccessful()) {
// Update the username
UserProfileChangeRequest updateRequest =
new UserProfileChangeRequest.Builder()
.setDisplayName(firstName)
.build();
auth.getCurrentUser().updateProfile(updateRequest).addOnCompleteListener(new OnCompleteListener<Void>() {
@Override
public void onComplete(@NonNull Task<Void> task) {
startActivity(new Intent(SignupActivity.this, LoginActivity.class));
finish();
}
});
} else {
//user.delete();
Toast.makeText(SignupActivity.this,
"Could not add the user to the database", Toast.LENGTH_SHORT).show();
}
}
});
}
}
});
}
});
}
}
activity_signup.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".SignupActivity">
<EditText
android:layout_width="0dp"
android:layout_height="wrap_content"
android:inputType="textPersonName"
android:ems="10"
android:id="@+id/txtfname"
android:hint="First Name" android:layout_marginTop="8dp" app:layout_constraintTop_toTopOf="parent"
android:layout_marginEnd="8dp" app:layout_constraintEnd_toEndOf="parent" android:layout_marginRight="8dp"
android:layout_marginStart="8dp" app:layout_constraintStart_toStartOf="parent"
android:layout_marginLeft="8dp" android:layout_marginBottom="8dp"
app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintVertical_bias="0.017"/>
<EditText
android:layout_width="0dp"
android:layout_height="wrap_content"
android:inputType="textPersonName"
android:ems="10"
android:id="@+id/txtlname" android:layout_marginTop="8dp"
app:layout_constraintTop_toBottomOf="@+id/txtfname" android:layout_marginBottom="8dp"
app:layout_constraintBottom_toBottomOf="parent" android:layout_marginEnd="8dp"
app:layout_constraintEnd_toEndOf="parent" android:layout_marginRight="8dp" android:layout_marginStart="8dp"
app:layout_constraintStart_toStartOf="parent" android:layout_marginLeft="8dp"
app:layout_constraintHorizontal_bias="0.0" app:layout_constraintVertical_bias="0.0"
android:hint="Last Name"/>
<EditText
android:layout_width="0dp"
android:layout_height="wrap_content"
android:inputType="textPassword"
android:ems="10"
android:id="@+id/txtpass" android:layout_marginBottom="8dp"
app:layout_constraintBottom_toBottomOf="parent" android:layout_marginTop="8dp"
app:layout_constraintTop_toBottomOf="@+id/txtlname" android:layout_marginEnd="8dp"
app:layout_constraintEnd_toEndOf="parent" android:layout_marginRight="8dp" android:layout_marginStart="8dp"
app:layout_constraintStart_toStartOf="parent" android:layout_marginLeft="8dp"
app:layout_constraintHorizontal_bias="0.0" app:layout_constraintVertical_bias="0.0"
android:hint="Password"/>
<EditText
android:layout_width="0dp"
android:layout_height="wrap_content"
android:inputType="textEmailAddress"
android:ems="10"
android:id="@+id/txtemail" app:layout_constraintEnd_toEndOf="parent"
android:layout_marginEnd="8dp" android:layout_marginRight="8dp"
app:layout_constraintStart_toStartOf="parent" android:layout_marginLeft="8dp"
android:layout_marginStart="8dp" android:layout_marginBottom="8dp"
app:layout_constraintBottom_toBottomOf="parent" android:layout_marginTop="8dp"
app:layout_constraintTop_toBottomOf="@+id/txtpass" app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintVertical_bias="0.0" android:hint="E-mail"/>
<EditText
android:layout_width="0dp"
android:layout_height="wrap_content"
android:inputType="phone"
android:ems="10"
android:id="@+id/txtphone" app:layout_constraintEnd_toEndOf="parent"
android:layout_marginEnd="8dp" android:layout_marginRight="8dp"
app:layout_constraintStart_toStartOf="parent" android:layout_marginLeft="8dp"
android:layout_marginStart="8dp" android:layout_marginBottom="8dp"
app:layout_constraintBottom_toBottomOf="parent" android:layout_marginTop="8dp"
app:layout_constraintTop_toBottomOf="@+id/txtemail" app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintVertical_bias="0.0" android:hint="Phone Number"/>
<View
android:id="@+id/divider3"
android:layout_width="368dp"
android:layout_height="1dp"
android:layout_marginStart="8dp"
android:layout_marginLeft="8dp"
android:layout_marginTop="8dp"
android:layout_marginEnd="8dp"
android:layout_marginRight="8dp"
android:layout_marginBottom="152dp"
android:background="?android:attr/listDivider"
android:visibility="visible"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/txtphone"
app:layout_constraintVertical_bias="0.0" />
<Button
android:id="@+id/btnreg"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="8dp"
android:layout_marginLeft="8dp"
android:layout_marginTop="8dp"
android:layout_marginEnd="8dp"
android:layout_marginRight="8dp"
android:layout_marginBottom="8dp"
android:text="Registration"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/divider3"
app:layout_constraintVertical_bias="0.0" />
</android.support.constraint.ConstraintLayout>
AndroidMainfest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.kiit.shoppar">
<uses-permission android:name="android.permission.INTERNET" />
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".SignupActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".LoginActivity" />
<activity android:name=".MainActivity"></activity>
</application>
</manifest>
错误
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.kiit.shoppar, PID: 14665
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.example.kiit.shoppar.SignupActivity$1.onClick(SignupActivity.java:90)
at android.view.View.performClick(View.java:6294)
at android.view.View.onKeyUp(View.java:12470)
at android.widget.TextView.onKeyUp(TextView.java:7475)
at android.view.KeyEvent.dispatch(KeyEvent.java:2715)
at android.view.View.dispatchKeyEvent(View.java:11713)
at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1834)
at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1834)
at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1834)
at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1834)
at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1834)
at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1834)
at com.android.internal.policy.DecorView.superDispatchKeyEvent(DecorView.java:440)
at com.android.internal.policy.PhoneWindow.superDispatchKeyEvent(PhoneWindow.java:1819)
at android.app.Activity.dispatchKeyEvent(Activity.java:3267)
at android.support.v7.app.AppCompatActivity.dispatchKeyEvent(AppCompatActivity.java:534)
at android.support.v7.view.WindowCallbackWrapper.dispatchKeyEvent(WindowCallbackWrapper.java:58)
at android.support.v7.app.AppCompatDelegateImplBase$AppCompatWindowCallbackBase.dispatchKeyEvent(AppCompatDelegateImplBase.java:316)
at com.android.internal.policy.DecorView.dispatchKeyEvent(DecorView.java:354)
at android.view.ViewRootImpl$ViewPostImeInputStage.processKeyEvent(ViewRootImpl.java:4733)
at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:4605)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:4147)
at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:4200)
at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:4166)
at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:4293)
at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:4174)
at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:4350)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:4147)
at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:4200)
at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:4166)
at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:4174)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:4147)
at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:4200)
at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:4166)
at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:4326)
at android.view.ViewRootImpl$ImeInputStage.onFinishedInputEvent(ViewRootImpl.java:4487)
at android.view.inputmethod.InputMethodManager$PendingEvent.run(InputMethodManager.java:2435)
at android.view.inputmethod.InputMethodManager.invokeFinishedInputEventCallback(InputMethodManager.java:1998)
at android.view.inputmethod.InputMethodManager.finishedInputEvent(InputMethodManager.java:1989)
at android.view.inputmethod.InputMethodManager$ImeInputEventSender.onInputEventFinished(InputMethodManager.java:2412)
at android.view.InputEventSender.dispatchInputEventFinished(InputEventSender.java:141)
at android.os.MessageQueue.nativePollOnce(Native Method)
at android.os.MessageQueue.next(MessageQueue.java:325)
at android.os.Looper.loop(Looper.java:142)
at android.app.ActivityThread.main(ActivityThread.java:6494)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
Application terminated.