如何在Flutter Firebase App中捕获DatabaseError [英] How to catch DatabaseError in Flutter Firebase App

问题描述

我正在学习Flutter，我想捕捉应该在Flutter应用程序/设备上抛出的异常（因为安全规则正确地拒绝了它）。

I am learning Flutter and I want to catch the exception that should be thrown ( as security rule is correctly rejecting it) at the Flutter Application/device.

下面是代码

   try {
      FirebaseDatabase.instance.reference().once().then((DataSnapshot snapshot) {
        try {
        debugPrint(snapshot.toString());
        }
        on DatabaseError catch (eIn1) {
        debugPrint(' onRoot ' + eIn1.toString());
        }
      });
    }on DatabaseError catch (eOut1) {
      debugPrint(' on1 ' + eOut1.toString());
    }

    try {
      FirebaseDatabase.instance.reference().child("todo").once().then((DataSnapshot snapshot) {
        try {
          debugPrint(snapshot.toString());
        }
        on DatabaseError catch (eIn2) {
          debugPrint(' onNode ' + eIn2.toString());
        }
      });
    }on Exception catch (eOut2) {
      debugPrint(' on2 ' + eOut2.toString());
    }

但是Android Studio从未抛出或捕获异常，在logCat I中可以看到异常，

But the Exception is never thrown or catch by the Android Studio, In logCat I can see the exception,

com.example.flutterlogindemo E / flutter：
[错误：flutter / lib / ui / ui_dart_state .cc（157）]未处理的异常：
DatabaseError（-3，权限被拒绝，）
＃0 Query.once（package：firebase_database / src / query.dart：84：41）

＃1 _HomePageState.initState（package：flutter_login_demo / pages / home_page.dart：48：65）

com.example.flutterlogindemo E/flutter: [ERROR:flutter/lib/ui/ui_dart_state.cc(157)] Unhandled Exception: DatabaseError(-3, Permission denied, ) #0 Query.once (package:firebase_database/src/query.dart:84:41) #1 _HomePageState.initState (package:flutter_login_demo/pages/home_page.dart:48:65)

但不能

推荐答案

您可以使用 catchError 以捕获错误：

You can use the catchError to be able to catch the error:

FirebaseDatabase.instance.reference().child("todo").once().then((DataSnapshot snapshot) {
    print(snapshot);
})
.catchError((error) {
    print("Something went wrong: ${error.message}");
  });

https://api.flutter.dev/flutter/package-async_async/DelegatingFuture/catchError.html

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