我尝试将Firebase Auth的登录活动实施到我的主项目中，作为独立登录活动，当我在新项目上对其进行测试时，身份验证就可以正常工作。但是当我尝试在主项目中实现它时，它给出了一个空指针异常。
错误：
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 com.test.testbv.Login.onCreate(Login.java:47)
这是MainActivity.Java，它在其中检查用户是否在onCreate上得到了授权，否则它将使用户进入Login活动。
package com.test.testbv;
import android.content.Intent;
import android.os.Bundle;
import android.support.design.widget.NavigationView;
import android.support.v4.view.GravityCompat;
import android.support.v4.view.MenuItemCompat;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBar;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.PopupMenu;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.SearchView;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import com.firebase.ui.database.FirebaseRecyclerAdapter;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.Query;
public class MainActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {
RecyclerView mRecyclerView;
FirebaseDatabase mFirebaseDatabase;
DatabaseReference mRef;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
FirebaseAuth.getInstance().getCurrentUser();
if (FirebaseAuth.getInstance().getCurrentUser() != null) {
// User is signed in.
} else {
// No user is signed in.
redirectToLogin();
}
// Action Bar
ActionBar actionBar = getSupportActionBar();
actionBar.setTitle("Coupons List");
mRecyclerView = findViewById(R.id.recyclerView);
mRecyclerView.setHasFixedSize(true);
// Set Layout
mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
// Send Query to Firebase Db
mFirebaseDatabase = FirebaseDatabase.getInstance();
mRef = mFirebaseDatabase.getReference("Data");
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.addDrawerListener(toggle);
toggle.syncState();
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
}
@Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
}
}
public void redirectToLogin () {
Intent intent = new Intent(this, Login.class);
startActivity(intent);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
// getMenuInflater().inflate(R.menu.main, menu);
// return true;
// Inflates the menu; this adds items to the action bar if it's present
getMenuInflater().inflate(R.menu.menu, menu);
MenuItem item = menu.findItem(R.id.action_search);
// Filter
// getMenuInflater().inflate(R.menu.menu, menu);
MenuItem itemFilter = menu.findItem(R.id.filterMenu);
SearchView searchView = (SearchView) MenuItemCompat.getActionView(item);
searchView.setOnQueryTextListener(new SearchView.OnQueryTextListener() {
@Override
public boolean onQueryTextSubmit(String query) {
firebaseSearch(query);
return false;
}
@Override
public boolean onQueryTextChange(String newText) {
// Filters down as you type
firebaseSearch(newText);
return false;
}
});
return super.onCreateOptionsMenu(menu);
}
@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();
if (id == R.id.nav_camera) {
// Handle the camera action
} else if (id == R.id.nav_gallery) {
} else if (id == R.id.nav_slideshow) {
} else if (id == R.id.nav_manage) {
} else if (id == R.id.nav_share) {
} else if (id == R.id.nav_send) {
}
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
// Filter Data
private void firebaseFilter(String searchText) {
String query = searchText.toLowerCase();
Query firebaseFilterQuery = mRef.orderByChild("category").startAt(query).endAt(query + "\uf8ff");
FirebaseRecyclerAdapter<Model, ViewHolder> firebaseRecyclerAdapter =
new FirebaseRecyclerAdapter<Model, ViewHolder>(
Model.class,
R.layout.row,
ViewHolder.class,
firebaseFilterQuery
) {
@Override
protected void populateViewHolder(ViewHolder viewHolder, Model model, int position) {
viewHolder.setDetails(getApplicationContext(), model.getTitle(), model.getDescription(), model.getImage());
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
ViewHolder viewHolder = super.onCreateViewHolder(parent, viewType);
viewHolder.setOnClickListener(new ViewHolder.clickListener() {
@Override
public void onItemClick(View view, int position) {
// get Data from firebase at the position clicked
String mTitle = getItem(position).getTitle();
String mDesc = getItem(position).getDescription();
String mImage = getItem(position).getImage();
// Pass this data to new activity
Intent intent = new Intent(view.getContext(), PostDetailActivity.class);
intent.putExtra("image", mImage);
intent.putExtra("title", mTitle);
intent.putExtra("description", mDesc);
startActivity(intent);
}
@Override
public void onItemLongClick(View view, int position) {
}
});
return viewHolder;
}
};
mRecyclerView.setAdapter(firebaseRecyclerAdapter);
}
@Override
protected void onStart() {
super.onStart();
FirebaseRecyclerAdapter<Model, ViewHolder> firebaseRecyclerAdapter =
new FirebaseRecyclerAdapter<Model, ViewHolder>(
Model.class,
R.layout.row,
ViewHolder.class,
mRef
) {
@Override
protected void populateViewHolder(ViewHolder viewHolder, Model model, int position) {
viewHolder.setDetails(getApplicationContext(), model.getTitle(), model.getDescription(), model.getImage());
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
ViewHolder viewHolder = super.onCreateViewHolder(parent, viewType);
viewHolder.setOnClickListener(new ViewHolder.clickListener() {
@Override
public void onItemClick(View view, int position) {
// get Data from firebase at the position clicked
String mTitle = getItem(position).getTitle();
String mDesc = getItem(position).getDescription();
String mImage = getItem(position).getImage();
// Pass this data to new activity
Intent intent = new Intent(view.getContext(), PostDetailActivity.class);
intent.putExtra("image", mImage);
intent.putExtra("title", mTitle);
intent.putExtra("description", mDesc);
startActivity(intent);
}
@Override
public void onItemLongClick(View view, int position) {
}
});
return viewHolder;
}
};
// Set adapter to recycler view
mRecyclerView.setAdapter(firebaseRecyclerAdapter);
}
}
具有以下.xml的登录活动：
package com.test.testbv;
import android.content.Intent;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.TextUtils;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
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;
public class Login extends AppCompatActivity implements View.OnClickListener {
private static final String TAG = "EmailPassword";
private TextView mStatusTextView;
private TextView mDetailTextView;
private EditText mEmailField;
private EditText mPasswordField;
// [START declare_auth]
private FirebaseAuth mAuth;
// [END declare_auth]
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Views
mStatusTextView = findViewById(R.id.status);
mDetailTextView = findViewById(R.id.detail);
mEmailField = findViewById(R.id.fieldEmail);
mPasswordField = findViewById(R.id.fieldPassword);
// Buttons
findViewById(R.id.emailSignInButton).setOnClickListener(this);
findViewById(R.id.emailCreateAccountButton).setOnClickListener(this);
findViewById(R.id.signOutButton).setOnClickListener(this);
findViewById(R.id.verifyEmailButton).setOnClickListener(this);
// [START initialize_auth]
mAuth = FirebaseAuth.getInstance();
// [END initialize_auth]
}
// [START on_start_check_user]
@Override
public void onStart() {
super.onStart();
// Check if user is signed in (non-null) and update UI accordingly.
FirebaseUser currentUser = mAuth.getCurrentUser();
updateUI(currentUser);
}
// [END on_start_check_user]
private void createAccount(String email, String password) {
Log.d(TAG, "createAccount:" + email);
if (!validateForm()) {
return;
}
// showProgressDialog();
// [START create_user_with_email]
mAuth.createUserWithEmailAndPassword(email, password)
.addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
@Override
public void onComplete(@NonNull Task<AuthResult> task) {
if (task.isSuccessful()) {
// Sign in success, update UI with the signed-in user's information
Log.d(TAG, "createUserWithEmail:success");
FirebaseUser user = mAuth.getCurrentUser();
updateUI(user);
} else {
// If sign in fails, display a message to the user.
Log.w(TAG, "createUserWithEmail:failure", task.getException());
Toast.makeText(Login.this, "Authentication failed.",
Toast.LENGTH_SHORT).show();
updateUI(null);
}
// [START_EXCLUDE]
// hideProgressDialog();
// [END_EXCLUDE]
}
});
// [END create_user_with_email]
}
private void signIn(String email, String password) {
Log.d(TAG, "signIn:" + email);
if (!validateForm()) {
return;
}
// showProgressDialog();
// [START sign_in_with_email]
mAuth.signInWithEmailAndPassword(email, password)
.addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
@Override
public void onComplete(@NonNull Task<AuthResult> task) {
if (task.isSuccessful()) {
// Sign in success, update UI with the signed-in user's information
Log.d(TAG, "signInWithEmail:success");
FirebaseUser user = mAuth.getCurrentUser();
updateUI(user);
redirectToMain();
} else {
// If sign in fails, display a message to the user.
Log.w(TAG, "signInWithEmail:failure", task.getException());
Toast.makeText(Login.this, "Authentication failed.",
Toast.LENGTH_SHORT).show();
updateUI(null);
}
// [START_EXCLUDE]
if (!task.isSuccessful()) {
mStatusTextView.setText(R.string.auth_failed);
}
// hideProgressDialog();
// [END_EXCLUDE]
}
});
// [END sign_in_with_email]
}
private void signOut() {
mAuth.signOut();
updateUI(null);
}
public void redirectToMain() {
Intent intent = new Intent(this, MainActivity.class);
startActivity(intent);
}
private void sendEmailVerification() {
// Disable button
findViewById(R.id.verifyEmailButton).setEnabled(false);
// Send verification email
// [START send_email_verification]
final FirebaseUser user = mAuth.getCurrentUser();
user.sendEmailVerification()
.addOnCompleteListener(this, new OnCompleteListener<Void>() {
@Override
public void onComplete(@NonNull Task<Void> task) {
// [START_EXCLUDE]
// Re-enable button
findViewById(R.id.verifyEmailButton).setEnabled(true);
if (task.isSuccessful()) {
Toast.makeText(Login.this,
"Verification email sent to " + user.getEmail(),
Toast.LENGTH_SHORT).show();
} else {
Log.e(TAG, "sendEmailVerification", task.getException());
Toast.makeText(Login.this,
"Failed to send verification email.",
Toast.LENGTH_SHORT).show();
}
// [END_EXCLUDE]
}
});
// [END send_email_verification]
}
private boolean validateForm() {
boolean valid = true;
String email = mEmailField.getText().toString();
if (TextUtils.isEmpty(email)) {
mEmailField.setError("Required.");
valid = false;
} else {
mEmailField.setError(null);
}
String password = mPasswordField.getText().toString();
if (TextUtils.isEmpty(password)) {
mPasswordField.setError("Required.");
valid = false;
} else {
mPasswordField.setError(null);
}
return valid;
}
private void updateUI(FirebaseUser user) {
// hideProgressDialog();
if (user != null) {
mStatusTextView.setText(getString(R.string.emailpassword_status_fmt,
user.getEmail(), user.isEmailVerified()));
mDetailTextView.setText(getString(R.string.firebase_status_fmt, user.getUid()));
findViewById(R.id.emailPasswordButtons).setVisibility(View.GONE);
findViewById(R.id.emailPasswordFields).setVisibility(View.GONE);
findViewById(R.id.signedInButtons).setVisibility(View.VISIBLE);
findViewById(R.id.verifyEmailButton).setEnabled(!user.isEmailVerified());
} else {
mStatusTextView.setText(R.string.signed_out);
mDetailTextView.setText(null);
findViewById(R.id.emailPasswordButtons).setVisibility(View.VISIBLE);
findViewById(R.id.emailPasswordFields).setVisibility(View.VISIBLE);
findViewById(R.id.signedInButtons).setVisibility(View.GONE);
}
}
@Override
public void onClick(View v) {
int i = v.getId();
if (i == R.id.emailCreateAccountButton) {
createAccount(mEmailField.getText().toString(), mPasswordField.getText().toString());
} else if (i == R.id.emailSignInButton) {
signIn(mEmailField.getText().toString(), mPasswordField.getText().toString());
} else if (i == R.id.signOutButton) {
signOut();
} else if (i == R.id.verifyEmailButton) {
sendEmailVerification();
}
}
}
以下XML：
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/main_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:weightSum="4">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="3"
android:gravity="center_horizontal"
android:orientation="vertical">
<TextView
android:id="@+id/titleText"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/emailpassword_title_text" />
<TextView
android:id="@+id/status"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/signed_out" />
<TextView
android:id="@+id/detail"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
tools:text="Firebase User ID: 123456789abc" />
</LinearLayout>
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:gravity="center_vertical">
<LinearLayout
android:id="@+id/emailPasswordFields"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:paddingLeft="16dp"
android:paddingRight="16dp">
<EditText
android:id="@+id/fieldEmail"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:hint="@string/hint_email"
android:inputType="textEmailAddress" />
<EditText
android:id="@+id/fieldPassword"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:hint="@string/hint_password"
android:inputType="textPassword" />
</LinearLayout>
<LinearLayout
android:id="@+id/emailPasswordButtons"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@+id/emailPasswordFields"
android:orientation="horizontal"
android:paddingLeft="16dp"
android:paddingRight="16dp">
<Button
android:id="@+id/emailSignInButton"
style="@style/Widget.AppCompat.Button.Colored"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="@string/sign_in" />
<Button
android:id="@+id/emailCreateAccountButton"
style="@style/Widget.AppCompat.Button.Colored"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="@string/create_account" />
</LinearLayout>
<LinearLayout
android:id="@+id/signedInButtons"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:orientation="horizontal"
android:paddingLeft="16dp"
android:paddingRight="16dp"
android:visibility="gone"
android:weightSum="2.0">
<Button
android:id="@+id/signOutButton"
style="@style/Widget.AppCompat.Button.Colored"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1.0"
android:text="@string/sign_out"
/>
<Button
android:id="@+id/verifyEmailButton"
style="@style/Widget.AppCompat.Button.Colored"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1.0"
android:text="@string/verify_email"
/>
</LinearLayout>
</RelativeLayout>
</LinearLayout>
Android清单：
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.test.testbv">
<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=".MainActivity"
android:label="@string/app_name"
android:theme="@style/AppTheme.NoActionBar">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.DEFAULT"/>
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".PostDetailActivity" />
<activity android:name=".FAQ" />
<activity android:name=".Login" />
</application>
</manifest>
答案 0 :(得分：1)
您已在登录屏幕中使用activity_main布局。