Question

在这个程序中，我将一个数组元素（flag1 [0]）的值设置为1，如果满足'if'条件。当我打印它（在类中）时，它显示值集但是当我试图在内部类之外访问它时，它显示值为0.我该如何解决它？（getCount（）和setCount（）是getter和setter，即使它们不起作用！）

public boolean checkUser(final String user, String program) {

    database = FirebaseDatabase.getInstance();
    final DatabaseReference reference;

    reference = database.getReference("UserNames").child(program);

    final int[] flag1 = {0};
    reference.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {


            for (DataSnapshot data : dataSnapshot.getChildren()) {

                String key = data.getKey();
                Log.println(Log.ERROR,"msg",key);

                if (data.getKey().equals(user))
                {
                    musername.setError("UserName already Exists1!");
                    flag1[0] = 1;
                    setCount(1);
                    Log.println(Log.ERROR,"msg", String.valueOf(flag1[0])+String.valueOf(getCount()));//Shows 1 here

                }
            }

        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });

    Log.println(Log.ERROR,"mesg", String.valueOf(flag1[0])+String.valueOf(getCount()));//Shows 0 here
    if(getCount()==0)
        return true;
    return  false;


}

Answer 1

由于if response.css(NAME_SELECTOR).extract_first(): #Checks to see if the company name field has data if not prints 'No results found' result = { 'Company Name': response.css(NAME_SELECTOR).extract_first(), 'Location' : response.xpath(LOCATION_SELECTOR)[0].extract(), #Location comes first inside the td tags thus the [0] 'Sales' : response.xpath(SALES_SELECTOR)[1].extract(), } else: result = { 'Company Name': response.css("dd.value.term::text").extract_first(), #identifies company name which data was not found 'Location': 'Not Found', 'Sales': 'Not Found' } # do something with result ... # or just: return result方法的异步行为，您不能简单地使用以下代码行：

onDataChange()

在该方法之外，因为它始终是Log.println(Log.ERROR,"mesg", String.valueOf(flag1[0])+String.valueOf(getCount()));。 Here了解更多信息。

要解决此问题，请仅在该方法中使用该值，您的问题将得到解决。否则，尝试理解异步概念，并从post

中查看我的答案

在匿名内部类中保留变量的值

1 个答案: