请帮我解决一些小问题,我确信你能做到:D
我正在尝试在 firestore 文档“user_cases_information”上设置一个字段,其中包含“case_number”字段
- 首先我声明这个全局变量
private String case_number_consecutive = new String("");
- 在
.setOnClickListener
中我有这个:(从其他文档读取旧的连续编号或案例编号)
if (service_type.equals("support")){
DocumentReference docRef = firestore_popup.collection("param_data_app").document("support_case_numbers");
docRef.get().addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() {
@Override
public void onComplete(@NonNull Task<DocumentSnapshot> task) {
if (task.isSuccessful()) {
DocumentSnapshot document = task.getResult();
String consecutive = document.get("consecutive").toString();
if (consecutive.equals(null)) {
int random = new Random().nextInt(117) + 4;
case_number_consecutive = "IOC-09"+random;
} else {
case_number_consecutive = consecutive; UpdateCaseNumbersConsecutive("support");
}
} else {
int random = new Random().nextInt(117) + 4;
case_number_consecutive = "IOC-09"+random;
}
}
});
}
Map<String, Object> user_cases_information = new HashMap<>();
user_cases_information.put("case_number", case_number_consecutive);
... (then i use a firestore reference to put the new case number)
假设当我检查 firestore 时,正是我设置“user_cases_information”文档的文档,我应该看到数字或新的 case_number,但我总是得到一个 null
引用,该字段连续总是 = null
为什么我得到这个空值?我用了一个 toast 并将其放在这之前:
Toast.makeText(...."Value: "+case_number_consecutive
Map<String, Object> user_cases_information = new HashMap<>();
user_cases_information.put("case_number", case_number_consecutive);
并且它显示null
,因此上述函数中的值或数据正在丢失
我该如何解决这个问题???万分感谢。
最佳答案
这样做的原因是因为 firebase 是异步执行的,而您在编码时就好像这一切都是同步发生的。这是什么意思 ?这意味着 firebase 调用不会立即从服务器返回值,需要一些时间才能获取该值,但其余代码在响应返回之前正在执行,这就是您遇到问题的原因。因此,即使此代码执行:
if (service_type.equals("support")){
DocumentReference docRef = firestore_popup.collection("param_data_app").document("support_case_numbers");
docRef.get().addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() {
@Override
public void onComplete(@NonNull Task<DocumentSnapshot> task) {
if (task.isSuccessful()) {
DocumentSnapshot document = task.getResult();
String consecutive = document.get("consecutive").toString();
if (consecutive.equals(null)) {
int random = new Random().nextInt(117) + 4;
case_number_consecutive = "IOC-09"+random;
} else {
case_number_consecutive = consecutive; UpdateCaseNumbersConsecutive("support");
}
} else {
int random = new Random().nextInt(117) + 4;
case_number_consecutive = "IOC-09"+random;
}
}
});
}
当响应返回时,您的其他代码:
Map<String, Object> user_cases_information = new HashMap<>();
user_cases_information.put("case_number", case_number_consecutive);
已经完成并调用,然后你永远不会从 firebase 获得实际值。
看看我的答案:How to add results of Facebook Graph api to array list in Java如果您需要帮助,我会帮助您制作类似的东西
您可以执行以下操作:
interface Callback{
void firebaseResponseCallback(String result);//whatever your return type is.
}
更改此方法的签名,如下所示:
public void getCaseNumber(Callback callback) {
将您的代码更改为:
if (service_type.equals("support")){
DocumentReference docRef = firestore_popup.collection("param_data_app").document("support_case_numbers");
docRef.get().addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() {
@Override
public void onComplete(@NonNull Task<DocumentSnapshot> task) {
if (task.isSuccessful()) {
DocumentSnapshot document = task.getResult();
String consecutive = document.get("consecutive").toString();
if (consecutive.equals(null)) {
int random = new Random().nextInt(117) + 4;
case_number_consecutive = "IOC-09"+random;
} else {
case_number_consecutive = consecutive; UpdateCaseNumbersConsecutive("support");
}
} else {
int random = new Random().nextInt(117) + 4;
case_number_consecutive = "IOC-09"+random;
}
callback.firebaseResponseCallback(case_number_consecutive);
}
});
}
然后,当您调用 getCaseNumber
时:
getCaseNumber(new Callback() {
@Override
public void firebaseResponseCallback(String result) {
here, this result parameter that comes through is your api call result to use, so result will be your case number, so make your objects inside this method, not outside
}
});
}
<小时/>
编辑
我专门针对这些类型的问题撰写了这篇文章: How to get data from any asynchronous operation in android
关于java - 使用全局变量从内部函数获取空字符串,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/59418348/