在MainActivity按logout button 之後到Login頁面的時候就停止application
這是Logcat
2020-06-20 22:41:15.081 7286-7286/com.example.myapplicationlastlast E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.myapplicationlastlast, PID: 7286
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.google.firebase.firestore.DocumentSnapshot.getString(java.lang.String)' on a null object reference
at com.example.myapplicationlastlast.MainActivity$1.onEvent(MainActivity.java:41)
at com.example.myapplicationlastlast.MainActivity$1.onEvent(MainActivity.java:38)
at com.google.firebase.firestore.DocumentReference.lambda$addSnapshotListenerInternal$2(com.google.firebase:firebase-firestore@@17.1.2:544)
at com.google.firebase.firestore.DocumentReference$$Lambda$3.onEvent(com.google.firebase:firebase-firestore@@17.1.2)
at com.google.firebase.firestore.util.ExecutorEventListener.lambda$onEvent$0(com.google.firebase:firebase-firestore@@17.1.2:42)
at com.google.firebase.firestore.util.ExecutorEventListener$$Lambda$1.run(com.google.firebase:firebase-firestore@@17.1.2)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6077)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:756)
MainActivity
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.firestore.DocumentReference;
import com.google.firebase.firestore.DocumentSnapshot;
import com.google.firebase.firestore.EventListener;
import com.google.firebase.firestore.FirebaseFirestore;
import com.google.firebase.firestore.FirebaseFirestoreException;
public class MainActivity extends AppCompatActivity {
TextView fullName,email,phone;
FirebaseAuth fAuth;
FirebaseFirestore fStore;
String userId;
@Override
protected void onCreate(Bundle savedlnstanceState) {
super.onCreate(savedlnstanceState);
setContentView(R.layout.activity_main);
phone = findViewById(R.id.profilePhone);
fullName = findViewById(R.id.profileName);
email = findViewById(R.id.profileEmail);
fAuth = FirebaseAuth.getInstance();
fStore = FirebaseFirestore.getInstance();
userId = fAuth.getCurrentUser().getUid();
DocumentReference documentReference = fStore.collection("users").document(userId);
documentReference.addSnapshotListener(this, new EventListener<DocumentSnapshot>() {
@Override
public void onEvent(@Nullable DocumentSnapshot documentSnapshot, @Nullable FirebaseFirestoreException e) {
phone.setText(documentSnapshot.getString("phone"));
fullName.setText(documentSnapshot.getString("fName"));
email.setText(documentSnapshot.getString("email"));
}
});
}
public void logout(View view) {
FirebaseAuth.getInstance().signOut();//logout
startActivity(new Intent(getApplicationContext(),Login.class));
finish();
}
}
Register
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import android.content.Intent;
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.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;
import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.OnFailureListener;
import com.google.android.gms.tasks.OnSuccessListener;
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.firestore.DocumentReference;
import com.google.firebase.firestore.FirebaseFirestore;
import java.util.HashMap;
import java.util.Map;
public class Register extends AppCompatActivity {
public static final String TAG = "TAG";
EditText mFullName,mEmail,mPassword,mPhone;
Button mRegisterBtn;
TextView mLoginBtn;
FirebaseAuth fAuth;
ProgressBar progressBar;
FirebaseFirestore fStore;
String userID;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_register);
mFullName = findViewById(R.id.fullName);
mEmail = findViewById(R.id.Email);
mPassword = findViewById(R.id.password);
mPhone = findViewById(R.id.phone);
mRegisterBtn= findViewById(R.id.registerBtn);
mLoginBtn = findViewById(R.id.createText);
fAuth = FirebaseAuth.getInstance();
fStore = FirebaseFirestore.getInstance();
progressBar = findViewById(R.id.progressBar);
if(fAuth.getCurrentUser() != null){
startActivity(new Intent(getApplicationContext(),MainActivity.class));
finish();
}
mRegisterBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
final String email = mEmail.getText().toString().trim();
String password = mPassword.getText().toString().trim();
final String fullName = mFullName.getText().toString();
final String phone = mPhone.getText().toString();
if(TextUtils.isEmpty(email)){
mEmail.setError("Email is Required.");
return;
}
if(TextUtils.isEmpty(password)){
mPassword.setError("Password is Required.");
return;
}
if(password.length() < 6){
mPassword.setError("Password Must be >= 6 Characters");
return;
}
progressBar.setVisibility(View.VISIBLE);
// register the user in firebase
fAuth.createUserWithEmailAndPassword(email,password).addOnCompleteListener(new OnCompleteListener<AuthResult>() {
@Override
public void onComplete(@NonNull Task<AuthResult> task) {
if(task.isSuccessful()){
// send verification link
FirebaseUser fuser = fAuth.getCurrentUser();
fuser.sendEmailVerification().addOnSuccessListener(new OnSuccessListener<Void>() {
@Override
public void onSuccess(Void aVoid) {
Toast.makeText(Register.this, "Verification Email Has been Sent.", Toast.LENGTH_SHORT).show();
}
}).addOnFailureListener(new OnFailureListener() {
@Override
public void onFailure(@NonNull Exception e) {
Log.d(TAG, "onFailure: Email not sent " + e.getMessage());
}
});
Toast.makeText(Register.this, "User Created.", Toast.LENGTH_SHORT).show();
userID = fAuth.getCurrentUser().getUid();
DocumentReference documentReference = fStore.collection("users").document(userID);
Map<String,Object> user = new HashMap<>();
user.put("fName",fullName);
user.put("email",email);
user.put("phone",phone);
documentReference.set(user).addOnSuccessListener(new OnSuccessListener<Void>() {
@Override
public void onSuccess(Void aVoid) {
Log.d(TAG, "onSuccess: user Profile is created for "+ userID);
}
}).addOnFailureListener(new OnFailureListener() {
@Override
public void onFailure(@NonNull Exception e) {
Log.d(TAG, "onFailure: " + e.toString());
}
});
startActivity(new Intent(getApplicationContext(),MainActivity.class));
}else {
Toast.makeText(Register.this, "Error ! " + task.getException().getMessage(), Toast.LENGTH_SHORT).show();
progressBar.setVisibility(View.GONE);
}
}
});
}
});
mLoginBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
startActivity(new Intent(getApplicationContext(),Login.class));
}
});
}
}
Login
import android.content.DialogInterface;
import android.content.Intent;
import android.os.Bundle;
import android.text.TextUtils;
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 androidx.annotation.NonNull;
import androidx.appcompat.app.AlertDialog;
import androidx.appcompat.app.AppCompatActivity;
import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.OnFailureListener;
import com.google.android.gms.tasks.OnSuccessListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.auth.AuthResult;
import com.google.firebase.auth.FirebaseAuth;
public class Login extends AppCompatActivity {
EditText mEmail,mPassword;
Button mLoginBtn;
TextView mCreateBtn,forgotTextLink;
ProgressBar progressBar;
FirebaseAuth fAuth;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);
mEmail = findViewById(R.id.Email);
mPassword = findViewById(R.id.password);
progressBar = findViewById(R.id.progressBar);
fAuth = FirebaseAuth.getInstance();
mLoginBtn = findViewById(R.id.loginBtn);
mCreateBtn = findViewById(R.id.createText);
forgotTextLink = findViewById(R.id.forgotPassword);
mLoginBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String email = mEmail.getText().toString().trim();
String password = mPassword.getText().toString().trim();
if(TextUtils.isEmpty(email)){
mEmail.setError("Email is Required.");
return;
}
if(TextUtils.isEmpty(password)){
mPassword.setError("Password is Required.");
return;
}
if(password.length() < 6){
mPassword.setError("Password Must be >= 6 Characters");
return;
}
progressBar.setVisibility(View.VISIBLE);
// authenticate the user
fAuth.signInWithEmailAndPassword(email,password).addOnCompleteListener(new OnCompleteListener<AuthResult>() {
@Override
public void onComplete(@NonNull Task<AuthResult> task) {
if(task.isSuccessful()){
Toast.makeText(Login.this, "Logged in Successfully", Toast.LENGTH_SHORT).show();
startActivity(new Intent(getApplicationContext(),MainActivity.class));
}else {
Toast.makeText(Login.this, "Error ! " + task.getException().getMessage(), Toast.LENGTH_SHORT).show();
progressBar.setVisibility(View.GONE);
}
}
});
}
});
mCreateBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
startActivity(new Intent(getApplicationContext(),Register.class));
}
});
forgotTextLink.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
final EditText resetMail = new EditText(v.getContext());
final AlertDialog.Builder passwordResetDialog = new AlertDialog.Builder(v.getContext());
passwordResetDialog.setTitle("Reset Password ?");
passwordResetDialog.setMessage("Enter Your Email To Received Reset Link.");
passwordResetDialog.setView(resetMail);
passwordResetDialog.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
// extract the email and send reset link
String mail = resetMail.getText().toString();
fAuth.sendPasswordResetEmail(mail).addOnSuccessListener(new OnSuccessListener<Void>() {
@Override
public void onSuccess(Void aVoid) {
Toast.makeText(Login.this, "Reset Link Sent To Your Email.", Toast.LENGTH_SHORT).show();
}
}).addOnFailureListener(new OnFailureListener() {
@Override
public void onFailure(@NonNull Exception e) {
Toast.makeText(Login.this, "Error ! Reset Link is Not Sent" + e.getMessage(), Toast.LENGTH_SHORT).show();
}
});
}
});
passwordResetDialog.setNegativeButton("No", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
// close the dialog
}
});
passwordResetDialog.create().show();
}
});
}
}
已邀請的邦友 {{ invite_list.length }}/5
根據這段來看
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.google.firebase.firestore.DocumentSnapshot.getString(java.lang.String)' on a null object reference
發生錯誤是因為在一個 DocumentSnapshot object(object是null) 執行 getString method
符合這兩個條件的
只有以下這段
public void onEvent(@Nullable DocumentSnapshot documentSnapshot, @Nullable FirebaseFirestoreException e) {
phone.setText(documentSnapshot.getString("phone"));
fullName.setText(documentSnapshot.getString("fName"));
email.setText(documentSnapshot.getString("email"));
}
所以你要倒推回去
檢查看看上一層的
DocumentReference documentReference = fStore.collection("users").document(userId);
是不是已經是 null 了
以致於往下的 DocumentSnapshot 物件也是 null
iThome鐵人賽
看影片追技術