从Android调用的Firebase云函数可以工作，但总是得到空响应

我试图调用一个Google Firebase云函数，该函数只需使用一个事务来检查Firestore中是否存在某些内容，然后删除它和另一个文档。我在安卓上点击一个按钮就调用了这个函数，它确实起作用了，条目被删除了，但是我在安卓上得到的响应是空的，而不是我试图发回的消息

云功能：

//Takes in the uid of the user who sent the request and the user who received it,
// and deletes the request
exports.cancelFriendRequest = functions.https.onCall((data, context) => {
    //Grab the parameters
    const sender = data.sender;
    const recipient = data.recipient;

    //Ensure parameters are good
    if(sender === undefined || sender === "" || recipient === undefined || recipient === "") {
        return res.status(400).send("Invalid arguments.");
    }

    const db = admin.firestore();

    //Build document references to check that friend request exists
    let receivedFriendRequestDocRef = db.doc("users/"+recipient+"/receivedFriendRequests/"+sender);
    let sentFriendRequestDocRef = db.doc("users/"+sender+"/sentFriendRequests/"+recipient);

    db.runTransaction(transaction => {
        return transaction.getAll(receivedFriendRequestDocRef, sentFriendRequestDocRef).then(docs => {
            //Check that the friend request exists
            if(!docs[0].exists) {
                return Promise.reject(new Error("Friend request does not exist."));
            }

            //Delete friend requests
            transaction.delete(receivedFriendRequestDocRef);
            transaction.delete(sentFriendRequestDocRef);

            return Promise.resolve("Friend request deleted successfully.");
        });
    }).then(result => {
        //I've also tried return res.status(200).send("Success: " + result);
        //But that wasn't working so I thought I'd try this, which I saw in a Google sample git repo
        return "Success: " + result;
    }).catch(err => {
        return err.toString();
    });
});

Android云函数调用：

public static Task<String> cancelFriendRequest(String sender, String recipient) {
        FirebaseFunctions mFunctions = FirebaseFunctions.getInstance();

        //Create the arguments to the callable function
        Map<String, Object> data = new HashMap<>();
        data.put("sender", sender);
        data.put("recipient", recipient);

        return mFunctions
                .getHttpsCallable("cancelFriendRequest")
                .call(data)
                .continueWith(new Continuation<HttpsCallableResult, String>() {
                    @Override
                    public String then(@NonNull Task<HttpsCallableResult> task) throws Exception {
                        //This continuation runs on either success or failure, but if the task
                        // has failed then getResult() will throw an Exception which will be
                        // propagated down.
                        String result = (String) task.getResult().getData();
                        return result;
                    }
                });
    }

公共静态任务取消请求（字符串发送方、字符串接收方）{
FirebaseFunctions mFunctions=FirebaseFunctions.getInstance（）；
//创建可调用函数的参数
映射数据=新的HashMap（）；
数据输入（“发送方”，发送方）；
数据输入（“收件人”，收件人）；
返回函数
.getHttpScalable（“取消请求”）
.呼叫（数据）
.continueWith（新的continueWith（）{
@凌驾
公共字符串（@NonNull Task）引发异常{
//此延续在成功或失败时运行，但如果任务
//失败，则getResult（）将引发异常，该异常将
//向下传播。
字符串结果=（字符串）task.getResult（）.getData（）；
返回结果；
}
});
}

Android中调用云函数的函数：

private static void cancelFriendRequest(String uid) {
    String userId = FirebaseAuth.getInstance().getCurrentUser().getUid();
    CloudFunctions.cancelFriendRequest(userId, uid).addOnCompleteListener(new OnCompleteListener<String>() {
        @Override
        public void onComplete(@NonNull Task<String> task) {
            String result = task.getResult();
            Log.e("Result", "" + result);
            Snackbar.make(mRecyclerView, result, Snackbar.LENGTH_LONG).show();
        }
    });
}

private静态无效取消请求（字符串uid）{
字符串userId=FirebaseAuth.getInstance（）.getCurrentUser（）.getUid（）；
cancelFriendRequest（userId，uid）.addOnCompleteListener（新的OnCompleteListener（）{
@凌驾
未完成的公共void（@NonNull任务）{
字符串结果=task.getResult（）；
Log.e（“结果”，“结果+结果”）；
Snackbar.make（mRecyclerView，result，Snackbar.LENGTH_LONG.show（）；
}
});
}

我很乐意提供更多的信息。我还发现调用这个函数非常慢。如果我将其设置为onRequest并通过手动导航到URL来调用它，它的工作速度会非常快，但是onCall和从Android调用速度非常慢。无论如何，这是另一个问题，谢谢

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编辑：此外，Snackbar会弹出（为空，因为它返回null），在文档实际从数据库中删除之前10-15秒。

您错过了主函数中的返回（在云函数代码中），因此该函数会在事务完成执行之前返回。从：

使用这些推荐的方法来管理您的产品的生命周期 职能：

解析执行异步处理的函数（也称为 作为“后台函数”），返回JavaScript承诺

尝试返回事务（

return db.runTransaction（transaction=>{….}）；

），它应该可以工作，如下所示：

//Takes in the uid of the user who sent the request and the user who received it,
// and deletes the request
exports.cancelFriendRequest = functions.https.onCall((data, context) => {
    //Grab the parameters
    const sender = data.sender;
    const recipient = data.recipient;

    //Ensure parameters are good
    if(sender === undefined || sender === "" || recipient === undefined || recipient === "") {
        return res.status(400).send("Invalid arguments.");
    }

    const db = admin.firestore();

    //Build document references to check that friend request exists
    let receivedFriendRequestDocRef = db.doc("users/"+recipient+"/receivedFriendRequests/"+sender);
    let sentFriendRequestDocRef = db.doc("users/"+sender+"/sentFriendRequests/"+recipient);

   return db.runTransaction(transaction => {
        return transaction.getAll(receivedFriendRequestDocRef, sentFriendRequestDocRef).then(docs => {
            //Check that the friend request exists
            if(!docs[0].exists) {
                return Promise.reject(new Error("Friend request does not exist."));
            }

            //Delete friend requests
            transaction.delete(receivedFriendRequestDocRef);
            transaction.delete(sentFriendRequestDocRef);

            return Promise.resolve("Friend request deleted successfully.");
        });
    }).then(result => {
        //I've also tried return res.status(200).send("Success: " + result);
        //But that wasn't working so I thought I'd try this, which I saw in a Google sample git repo
        return "Success: " + result;
    }).catch(err => {
        return err.toString();
    });
});

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非常感谢！我一定是直接忘记把它放在那里了，因为当我看到这是你的回答时，我可以发誓我已经归还了它，但唉，我没有。再次感谢！