java - 调用另一个方法后字符串值null android java

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私有(private)变量audioLink在调用setAudio()等另一个方法后为null，即使它在onComplete方法之外也是null。我厌倦了解决这个问题。

private String audioLink;

private void setData() {
        //FireBase Get Details Section
        firebaseFirestore = FirebaseFirestore.getInstance();
        firebaseFirestore.collection("SUBJECT")
                .document(subjectName).collection("CHAPTER")
                .document(chapterName.toUpperCase())
                .get().addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() {
            @Override
            public void onComplete(@NonNull Task<DocumentSnapshot> task) {
                if (task.isSuccessful()) {
                    DocumentSnapshot document = task.getResult();
                    if (document.exists()) {
                        txtDetails.setText(document.get("chapterDetails").toString());
                        audioLink = document.get("audioLink").toString();//Assigning Value
                    } else {
                        txtDetails.setText("Empty");
                    }
                } else {
                    Log.d("Error", "Cached get failed: ", task.getException());
                }
            }
        });
    }

private void setAudio() {
        try {
            String url = audioLink; // your URL here
        } catch (Exception e) {
        }
    }

Answer 1

您需要在 onComplete 方法中调用它:

private String audioLink;

private void setData() {
    //FireBase Get Details Section
    firebaseFirestore = FirebaseFirestore.getInstance();
    firebaseFirestore.collection("SUBJECT")
            .document(subjectName).collection("CHAPTER")
            .document(chapterName.toUpperCase())
            .get().addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() {
        @Override
        public void onComplete(@NonNull Task<DocumentSnapshot> task) {
            if (task.isSuccessful()) {
                DocumentSnapshot document = task.getResult();
                if (document.exists()) {
                    txtDetails.setText(document.get("chapterDetails").toString());
                    audioLink = document.get("audioLink").toString();//Assigning Value
                 setAudio(); // you need to call if from here 
                } else {
                    txtDetails.setText("Empty");
                }
            } else {
                Log.d("Error", "Cached get failed: ", task.getException());
            }
        }
    });
}