这可能是一个基本问题，但我无法弄清楚这一点。我的函数总是返回一个空值，我不知道为什么。
我的主代码（在不同的视图控制器中）使用＆＃34;字符串＆＃34;来调用此函数。寻找。但在功能结束时，我永远无法返回结果。如果我打印搜索结果，我有最终的打印声明，那么我确实看到了结果。但是在该函数完成之后，返回值为零。如何从此函数获取返回值？提前致谢，。我正在使用Swift btw。
EditText phoneNum,Code;// two edit text one for enter phone number other for enter OTP code
Button sent_,Verify; // sent button to request for verification and verify is for to verify code
private PhoneAuthProvider.ForceResendingToken mResendToken;
private PhoneAuthProvider.OnVerificationStateChangedCallbacks mCallbacks;
private FirebaseAuth mAuth;
private String mVerificationId;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_phone_number_auth);// layout
phoneNum =(EditText) findViewById(R.id.fn_num);
Code =(EditText) findViewById(R.id.code);
sent_ =(Button)findViewById(R.id.sent_nu);
Verify =(Button)findViewById(R.id.verify);
callback_verificvation(); ///function initialization
mAuth = FirebaseAuth.getInstance();
sent_.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String num=phoneNum.getText().toString();
startPhoneNumberVerification(num); // call function for receive OTP 6 digit code
}
});
Verify.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String code=Code.getText().toString();
verifyPhoneNumberWithCode(mVerificationId,code); //call function for verify code
}
});
}
private void startPhoneNumberVerification(String phoneNumber) {
// [START start_phone_auth]
PhoneAuthProvider.getInstance().verifyPhoneNumber(
phoneNumber, // Phone number to verify
60, // Timeout duration
TimeUnit.SECONDS, // Unit of timeout
this, // Activity (for callback binding)
mCallbacks); // OnVerificationStateChangedCallbacks
// [END start_phone_auth]
}
private void signInWithPhoneAuthCredential(PhoneAuthCredential credential) {
mAuth.signInWithCredential(credential)
.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
FirebaseUser user = task.getResult().getUser();
Toast.makeText(getApplicationContext(), "sign in successfull", Toast.LENGTH_SHORT).show();
// [START_EXCLUDE]
} else {
// Sign in failed, display a message and update the UI
if (task.getException() instanceof FirebaseAuthInvalidCredentialsException) {
// The verification code entered was invalid
}
}
}
});
}
private void verifyPhoneNumberWithCode(String verificationId, String code) {
// [START verify_with_code]
PhoneAuthCredential credential = PhoneAuthProvider.getCredential(verificationId, code);
// [END verify_with_code]
signInWithPhoneAuthCredential(credential);
}
private void callback_verificvation() {
mCallbacks = new PhoneAuthProvider.OnVerificationStateChangedCallbacks() {
@Override
public void onVerificationCompleted(PhoneAuthCredential credential) {
// This callback will be invoked in two situations:
// 1 - Instant verification. In some cases the phone number can be instantly
// verified without needing to send or enter a verification code.
// 2 - Auto-retrieval. On some devices Google Play services can automatically
// detect the incoming verification SMS and perform verificaiton without
// user action.
// [START_EXCLUDE silent]
// [START_EXCLUDE silent]
signInWithPhoneAuthCredential(credential);
}
@Override
public void onVerificationFailed(FirebaseException e) {
// This callback is invoked in an invalid request for verification is made,
// for instance if the the phone number format is not valid.
// [START_EXCLUDE silent]
if (e instanceof FirebaseAuthInvalidCredentialsException) {
// Invalid request
// [END_EXCLUDE]
} else if (e instanceof FirebaseTooManyRequestsException) {
// The SMS quota for the project has been exceeded
}
}
@Override
public void onCodeSent(String verificationId,
PhoneAuthProvider.ForceResendingToken token) {
// The SMS verification code has been sent to the provided phone number, we
// now need to ask the user to enter the code and then construct a credential
// by combining the code with a verification ID.
// Save verification ID and resending token so we can use them later
mVerificationId = verificationId;
mResendToken = token;
}
};
//你可以忽略以下所有这些，直到最后几行......
func fetchSearchResults (_ searchString: String) -> Array<Any> {
self.globalPost = [Posts]()
self.postKeysArray = []
var searchIndex:AlgoliaSearch.Index
let query = Query()
searchIndex = self.client.index(withName: "Comments")
//所以我的搜索代码在这里返回一些值，我在post keysArray中看到它们。
query.attributesToRetrieve = ["userComment","postId"]
query.attributesToHighlight = ["postId"]
query.query = searchString
query.optionalWords = [searchString]
let curSearchId = searchId
searchIndex.search(query, completionHandler: { (content, error) in
if (curSearchId <= self.displayedSearchId) || (error != nil) {
return // Newest query already displayed or error
}
self.displayedSearchId = curSearchId
self.loadedPage = 0 // Reset loaded page
guard let hits = content!["hits"] as? [[String: AnyObject]] else { return }
var tmp = [String]()
for hit in hits {
// print ("Comment is \(commentRecord(json:hit).postId)")
tmp.append(commentRecord(json:hit).postId!)
}
self.postKeysArray = tmp
self.getDatafromFirebase(searchString)
//但在这里我得到一个NULL值。
print ("Search Results -post keys is \(self.postKeysArray)") \\ returns correct values here in the Array
})
self.searchId += 1
答案 0 :(得分：0)
正如Alexander所说，您正在完成处理程序中打印搜索结果，该处理程序在fetchSearchResults返回时尚未执行。有几种不同的方法可以解决这个问题。一个是重构fetchSearchResults来进行封闭：
func fetchSearchResults (_ searchString: String, completionHandler completion: (Array<Any>) -> ()) {
// ...
searchIndex.search(query, completionHandler: { (content, error) in
// ...
self.postKeysArray = tmp
self.getDatafromFirebase(searchString)
// so my search code returns some values here and i see them in the post keysArray.
print ("Search Results -post keys is \(self.postKeysArray)") \\ returns correct values here in the Array
completion(self.postKeysArray)
})
}
然后，在您的“主要代码”中，无论您在哪里打电话：
let results = searchController.fetchSearchResults(searchString)
doSomething(with: results)
你现在有：
searchController.fetchSearchResults(searchString, { results in
doSomething(results)
})
这一行也可以写成：
searchController.fetchSearchResults(searchString, doSomething)
如果你真的不能让fetchSearchResults成为异步，那么你可以使用DispatchSemaphore等待完成处理程序完成：
func fetchSearchResults (_ searchString: String) -> Array<Any> {
// ...
var semaphore = DispatchSemaphore(0)
searchIndex.search(query, completionHandler: { (content, error) in
// ...
self.postKeysArray = tmp
self.getDatafromFirebase(searchString)
// so my search code returns some values here and i see them in the post keysArray.
print ("Search Results -post keys is \(self.postKeysArray)") \\ returns correct values here in the Array
semaphore.signal()
})
semaphore.wait()
return self.postKeysArray
}
请注意，除非您知道自己在做什么，否则使用信号量不是一个好主意。如果您不知道可能调用各种回调的线程，则可能导致死锁。如果在与searchIndex.search相同的DispatchQueue上调用fetchSearchResults完成处理程序，则上述示例将无效。如果你不明白我在说什么，你可能不应该这样做。使用异步回调几乎肯定会更好。