![](/img/trans.png)
[英]How to get key from QuerySnapshot in android firestore
[英]Android/FireStore QuerySnapshot convert to CustomObject
我目前programin測試QuizApp。 游戲玩法非常簡單我只想要一個問題的在線數據庫,用戶可以回答它們。
這就是數據庫的樣子:
該集合問題包含唯一ID和名為“content”的自定義對象(questionObject)。 這個數字只是我可以查詢/搜索的簡單內容。
這是我的問題添加和查詢UI。 這只是一個小測試App。
public class questionAdder擴展AppCompatActivity {
EditText pQuestion, pAnwerA, pAnswerB, pAnswerC, pAnswerD, number;
Button pAdd, query;
private DatabaseReference databaseReference;
private FirebaseFirestore firebaseFirestore;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.addquestion);
firebaseFirestore = FirebaseFirestore.getInstance();
pQuestion = (EditText) findViewById(R.id.question);
pAnwerA = (EditText) findViewById(R.id.answerA);
pAnswerB = (EditText) findViewById(R.id.answerB);
pAnswerC = (EditText) findViewById(R.id.answerC);
pAnswerD = (EditText) findViewById(R.id.answerD);
number = (EditText) findViewById(R.id.number);
pAdd = (Button) findViewById(R.id.addQuestion);
pAdd.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
readQuestionStore();
}
});
query = (Button) findViewById(R.id.query);
query.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
CollectionReference questionRef = firebaseFirestore.collection("questions");
questionRef.whereEqualTo("content.number", "20").get().addOnSuccessListener(new OnSuccessListener<QuerySnapshot>() {
@Override
public void onSuccess(QuerySnapshot queryDocumentSnapshots) {
questionObject pContent = queryDocumentSnapshots.toObjects(questionObject.class);
}
});
}
});
}
public void readQuestionStore(){
Map<String, Object> pContent = new HashMap<>();
pContent.put("question", pQuestion.getText().toString());
pContent.put("Corr Answer", pAnwerA.getText().toString());
pContent.put("AnswerB", pAnswerB.getText().toString());
pContent.put("AnswerC", pAnswerC.getText().toString());
pContent.put("AnswerD", pAnswerD.getText().toString());
questionObject content = new questionObject(pContent, number.getText().toString()); //document("Essen").collection("Katalog")
firebaseFirestore.collection("questions").add(content).addOnSuccessListener(new OnSuccessListener<DocumentReference>() {
@Override
public void onSuccess(DocumentReference documentReference) {
Toast.makeText(questionAdder.this, "Klappt", Toast.LENGTH_LONG).show();
}
}).addOnFailureListener(new OnFailureListener() {
@Override
public void onFailure(@NonNull Exception e) {
Toast.makeText(questionAdder.this, "Klappt nicht", Toast.LENGTH_LONG).show();
}
});
}
}
這就是我的questionObject的樣子:
public class questionObject {
private Map<String, Object> content;
private String number;
public questionObject(){
}
public questionObject(Map<String, Object> pContent, String pNumber) {
this.content = pContent;
this.number = pNumber;
}
public Map<String, Object> getContent() {
return content;
}
public void setContent(Map<String, Object> content) {
this.content = content;
}
public String getNumber() {
return number;
}
public void setNumber(String number) {
this.number = number;
}
}
問題在onClickListener中的questionAdder類中我收到“不兼容類型”錯誤(找到:java.utils.list必需:questionObject)。
query.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
CollectionReference questionRef = firebaseFirestore.collection("questions");
questionRef.whereEqualTo("content.number", "20").get().addOnSuccessListener(new OnSuccessListener<QuerySnapshot>() {
@Override
public void onSuccess(QuerySnapshot queryDocumentSnapshots) {
questionObject pContent = queryDocumentSnapshots.toObjects(questionObject.class);
}
});
}
});
如果我將其更改為List,則為空。 所以實際的問題是,如何使用數據庫將CustomObject放入我的代碼中。 謝謝!
您收到此錯誤的原因是因為QuerySnapshot
是一種“包含” 多個文檔的類型。 Firestore不會決定是否有一堆對象要返回,或者只返回一個。 這就是為什么你可以采取兩種不同的方法:
將數據放在custom object
的列表中:
List<questionObject> questionsList=new ArrayList<>(); if (!documentSnapshots.isEmpty()){ for (DocumentSnapshot snapshot:queryDocumentSnapshots) questionsList.add(snapshot.toObject(questionObject.class)); }
如果您確定只獲得一個查詢對象,則可以從返回的queryDocumentSnapshots
獲取第一個對象:
questionObject object=queryDocumentSnapshots.getDocuments().get(0).toObject(questionObject.class);
還有一些你應該注意的事情:
為什么要寫content.number
而不僅僅是number
? 似乎number
是問題document
的單獨字段,因此您的代碼應如下所示:
CollectionReference questionRef = firebaseFirestore.collection("questions");
questionRef.whereEqualTo("number", "20").get().addOnSuccessListener(new OnSuccessListener<QuerySnapshot>() {
@Override
public void onSuccess(QuerySnapshot queryDocumentSnapshots) {
questionObject pContent = queryDocumentSnapshots.toObjects(questionObject.class);
}
});
另外,嘗試將您的number
字段更改為int
,因為它不是String
而只是一個數字。
順便說一句,在開頭用大寫字母編寫類的名稱是更可接受的,例如: QuestionObject question=new QuestionObject();
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.