[英]Firestore get DocumentSnapshot's field's value
DocumentSnapshot有一個getString()方法,它接受字段的名稱並將其值作為字符串返回。
String value = document.getString("username");
您可以使用get
方法獲取字段的值
String username = (String) document.get("username"); //if the field is String
Boolean b = (Boolean) document.get("isPublic"); //if the field is Boolean
Integer i = (Integer) document.get("age") //if the field is Integer
您需要執行DocumentReference
才能獲取DocumentReference
中的內容。
一個簡單的會是這樣的。
DocumentReference docRef = myDB.collection("users").document("username");
docRef.get().addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() {
@Override
public void onComplete(@NonNull Task<DocumentSnapshot> task) {
if (task.isSuccessful()) {
DocumentSnapshot document = task.getResult();
if (document != null) {
Log.i("LOGGER","First "+document.getString("first"));
Log.i("LOGGER","Last "+document.getString("last"));
Log.i("LOGGER","Born "+document.getString("born"));
} else {
Log.d("LOGGER", "No such document");
}
} else {
Log.d("LOGGER", "get failed with ", task.getException());
}
}
});
缺點是您需要知道您的文檔 ID 才能獲取字段值。
當我在 onComplete 內部時,我只能將字段的數據作為字符串引用,但是當我嘗試在它外部引用它時。 我得到一個 nullPointerException 並且它使我的活動崩潰。
// Gets user document from Firestore as reference
DocumentReference docRef = mFirestore.collection("users").document(userID);
docRef.get().addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() {
@Override
public void onComplete(@NonNull Task<DocumentSnapshot> task) {
if (task.isSuccessful()) {
DocumentSnapshot document = task.getResult();
if (document.exists()) {
Log.d(TAG, "DocumentSnapshot data: " + document.getData());
Log.d(TAG, "db firstName getString() is: " + document.getString("firstName"));
Log.d(TAG, "db lastName getString() is: " + document.getString("lastName"));
mFirstName = (String) document.getString("firstName");
mLastName = (String) document.getString("lastName");
Log.d(TAG, "String mFirstName is: " + mFirstName);
Log.d(TAG, "String mLastName is: " + mLastName);
} else {
Log.d(TAG, "No such document");
}
} else {
Log.d(TAG, "get failed with ", task.getException());
}
}
});
//string checking outside the docRef.get().addOnCompleteListener code
//commented it out because it causes a java.lang.NullPointerException: println needs a message
//Log.v("NAME", mFirstName);
//Log.v("NAME", mLastName);
// sets the text on the TextViews
tvFirstName = (TextView)findViewById(R.id.tvFirstName);
tvFirstName.setText(mFirstName);
tvLastName = (TextView)findViewById(R.id.tvLastName);
tvLastName.setText(mLastName);
這是獲取文檔值的另一種簡單方法(在您的情況下):
Firestore.instance
.collection('users').document('xsajAansjdna')
.get()
.then((value) =>
print("Fetched ==>>>"+value.data["username"]));
`Firestore.instance
.collection('users').document('xsajAansjdna')
.get()
.then((value) =>
print("Fetched ==>>>"+value.data()["username"]));`
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