No Firebase App ‘[DEFAULT]‘ has been created - call Firebase.initializeApp() in Flutter and Firebase

• 問題原因

  裝有Firebase的程式沒有被初始化或者連接配接資料庫,貿然地進行cloud firestore事務會出現問題

• 解決方案(flutter - dart)

Widget InitiaFirebaseApp(){
return FutureBuilder(
          // 初始化 FlutterFire
          future: Firebase.initializeApp(),
          builder: (context, snapshot) {
            // 檢查錯誤
            if (snapshot.hasError) {
              print('hasError');
              return Center();
            }
            if (snapshot.connectionState == ConnectionState.done) {
              print('done');
              return Center();
            }

            //初始化完畢之後就可以進行Cloud Firestore的事務了
            return  Center(
              child: ElevatedButton(
                onPressed: (){
                  //将要完成Cloud Firestore的事務邏輯

                }, child: Text("Add"),
              ),
            );
          },
        );
        }