我在Android应用上使用Firebase;在我的signupActivity.class中创建用户时，我更新了currentUser用户名，并希望下一个活动MenuActivity.class获取当前用户ID和电子邮件，但我一直收到nullpointerException，这是错误：
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.sadainfo.apppfe/com.android.pfe.activity.MenuActivity}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2245)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2295)
at android.app.ActivityThread.access$700(ActivityThread.java:150)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1280)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:176)
at android.app.ActivityThread.main(ActivityThread.java:5279)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1102)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:869)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at com.android.pfe.activity.MenuActivity.onCreate(MenuActivity.java:89)
at android.app.Activity.performCreate(Activity.java:5267)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1097)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2209)
我创建用户的signupClass：
public class SignupActivity extends AppCompatActivity {
private static final String TAG ="SignupActivity" ;
private EditText mEmail,mPseudo,mMdp;
private Button mEnregistrer;
private FirebaseAuth auth;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
getSupportActionBar().hide();
auth=FirebaseAuth.getInstance();
final ArrayList<String> arrayList;
final ArrayAdapter<String> adapter;
final EditText txtinput ;
setContentView(R.layout.activity_signup);
ListView listView = (ListView)findViewById(R.id.ListV);
String [] item = {};
arrayList = new ArrayList<>(Arrays.asList(item));
adapter = new ArrayAdapter<String>(this,R.layout.list_item,R.id.txtitem,arrayList);
listView.setAdapter(adapter);
txtinput=(EditText)findViewById(R.id.txtinput);
Button btadd = (Button)findViewById(R.id.btadd);
btadd.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String newitem = txtinput.getText().toString();
arrayList.add(newitem);
adapter.notifyDataSetChanged();
}
});
setContentView(R.layout.activity_signup);
mEmail=(EditText)findViewById(R.id.email);
mPseudo=(EditText)findViewById(R.id.pseudo);
mMdp=(EditText)findViewById(R.id.mdp);
mEnregistrer=(Button) findViewById(R.id.enregCompte);
mEnregistrer.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
final String email = mEmail.getText().toString().trim();
String password = mMdp.getText().toString().trim();
final String pseudo =mPseudo.getText().toString().trim();
if (TextUtils.isEmpty(pseudo)) {
Toast.makeText(getApplicationContext(), "Entrer le pseudo", Toast.LENGTH_SHORT).show();
return;
}
if (TextUtils.isEmpty(email)) {
Toast.makeText(getApplicationContext(), "Entrer une adresse mail", Toast.LENGTH_SHORT).show();
return;
}
if (TextUtils.isEmpty(password)) {
Toast.makeText(getApplicationContext(), "Entrer un mot de passe", Toast.LENGTH_SHORT).show();
return;
}
if (password.length() < 6) {
Toast.makeText(getApplicationContext(), "mot de passe trop court, veuillez rentrer un minimum de 6 caractères", Toast.LENGTH_SHORT).show();
return;
}
//créating account
auth.createUserWithEmailAndPassword(email, password)
.addOnCompleteListener(SignupActivity.this, new OnCompleteListener<AuthResult>() {
@Override
public void onComplete(@NonNull Task<AuthResult> task) {
//progressBar.setVisibility(View.GONE);
if (task.isSuccessful()) {
Toast.makeText(SignupActivity.this, "Inscription réussie " + task.isSuccessful(), Toast.LENGTH_SHORT).show();
FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
if(user!=null) {
//changer les infos utilisateur
UserProfileChangeRequest profileUpdates = new UserProfileChangeRequest.Builder()
.setDisplayName(pseudo)
.build();
user.updateProfile(profileUpdates)
.addOnCompleteListener(new OnCompleteListener<Void>() {
@Override
public void onComplete(@NonNull Task<Void> task) {
if (task.isSuccessful()) {
Log.d(TAG, " profile updated.");
}
}
});
User uti = new User();
uti.addUser(user.getUid(), pseudo, email);
startActivity(new Intent(SignupActivity.this, MenuActivity.class));
finish();
}
//*****************************************************
} else {
Toast.makeText(SignupActivity.this, "erreur d'inscription" + task.getException().getMessage(),
Toast.LENGTH_SHORT).show();
}
}
});
}
});
}
和我在MenuActivity中的OnCreate方法，我调用CurrentUser来显示名称和电子邮件
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_menu);
toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
//get firebase auth instance
auth = FirebaseAuth.getInstance();
mHandler = new Handler();
drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
navigationView = (NavigationView) findViewById(R.id.nav_view);
// Navigation view header
navHeader = navigationView.getHeaderView(0);
txtName = (TextView) navHeader.findViewById(R.id.name);
txtWebsite = (TextView) navHeader.findViewById(R.id.job);
// imgNavHeaderBg = (ImageView) navHeader.findViewById(R.id.img_header_bg);
imgProfile = (ImageView) navHeader.findViewById(R.id.img_profile);
if(auth.getCurrentUser()!=null) {
if(auth.getCurrentUser().getDisplayName()!=null) {
txtName.setText(auth.getCurrentUser().getDisplayName().toString().trim());
} txtWebsite.setText(auth.getCurrentUser().getEmail().toString().trim());
}
profil=(TextView) navHeader.findViewById(R.id.Profil);
profil.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent insc = new Intent(MenuActivity.this,ProfilActivity.class);
startActivity(insc);
}
});
// load toolbar titles from string resources
activityTitles = getResources().getStringArray(R.array.nav_item_activity_titles);
// load nav menu header data
//loadNavHeader();
navigationView.getMenu().getItem(4).setActionView(R.layout.menu_dot);
// initializing navigation menu
setUpNavigationView();
if (savedInstanceState == null) {
navItemIndex = 0;
CURRENT_TAG = TAG_HOME;
loadHomeFragment();
}
}
调用txtName.setText(auth.getCurrentUser().getDisplayName().toString().trim());时发生错误
即使我用if语句测试了null。
编辑：我把txtName.setText(auth.getCurrentUser().getDisplayName().toString().trim());
在if语句中，现在名称在第一次启动时没有显示，我需要再次停止并启动应用程序。如何在第一次调用MenuActivity
答案 0 :(得分：-1)
您正在使用
txtName.setText(auth.getCurrentUser().getDisplayName().toString().trim());
改为使用
txtName.setText(auth.getInstance().getCurrentUser().getDisplayName().toString().trim());