Firebase空指针异常(Firebase null pointer exception)

 我在firebase中得到空指针异常我知道没有任何值，就像我给出的数据库引用那样但是我希望当生成该值时它会自动显示...只是想得到那个单值每次它在firebase上创建但它在行上给我空指针异常String val = ..... 
 
 请帮帮我 ... 
 
final DatabaseReference dtt = database.getReference("/trial/trials/");
    dtt.addValueEventListener(new ValueEventListener() {

        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            String val= dataSnapshot.child("myvalue").getValue().toString();
            if(val!=null)
            {
                Log.e("not null------","---------------");
            }else
            {
                Log.e("null------","---------------");
            }
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });
 
 请帮帮我......请.. 

I am getting null pointer exception in firebase I knows that there is not any value like that to which database reference I am giving but I wants that when the value is generated then it will be shown automatically... Just wants to get that single value everytime it is created on the firebase but its giving me null pointer exception on the line String val =.....
 
Please help me ...
 
final DatabaseReference dtt = database.getReference("/trial/trials/");
    dtt.addValueEventListener(new ValueEventListener() {

        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            String val= dataSnapshot.child("myvalue").getValue().toString();
            if(val!=null)
            {
                Log.e("not null------","---------------");
            }else
            {
                Log.e("null------","---------------");
            }
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });
 
Please help me.....Please ..

原文：https://stackoverflow.com/questions/38186051