Android Retrofit request how to get retrofit response in main Thread

Question

I use retrofit to get the response correctly, then I pass the response to an object in the response body, while it fails to get the object in UI thread, there is a NullPointerException Error, I think it's the problem of the asynchronous request, how can I avoid this problem?

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    button = findViewById(R.id.button);

    util = new Util(this);
    button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            util.login("sdjfl@gmail.com", "sdjflsdkf");

            // There is a NullPointerException? How Can I
            // use this methond correctly in this way?
            Log.d("user", util.getUserInfo().toString());
        }
    });
}

public class Util {
    private UserInfo userInfo;

    public UserInfo getUserInfo() {
        return userInfo;
    }

    public void login(final String email, final String password) {
        Call<UserInfo> loginCall = apiInterface.login(email, password);
        loginCall.enqueue(new Callback<UserInfo>() {
            @Override
            public void onResponse(Call<UserInfo> call, Response<UserInfo> response) {
                userInfo = response.body();
        }

        @Override
        public void onFailure(Call<UserInfo> call, Throwable t) {
        }
    });
}

elmorabea · Accepted Answer · 2017-12-03T00:26:45.670

0

Move this line inside the onResponse()

Log.d("user", util.getUserInfo().toString());

You are getting the user info object too realy, it's null at the point you are trying to access it

Like that

public class Util {
    public interface Callback {
        void onResponse(UserInfo info);
    }
    private UserInfo userInfo;

    public UserInfo getUserInfo() {
        return userInfo;
    }

    public void login(final String email, final String password, final Callback callback) {
        Call<UserInfo> loginCall = apiInterface.login(email, password);
        loginCall.enqueue(new Callback<UserInfo>() {
            @Override
            public void onResponse(Call<UserInfo> call, Response<UserInfo> response) {
                userInfo = response.body();
                callback.onResponse(userInfo);
                Log.d("user", userInfo.toString());
        }

        @Override
        public void onFailure(Call<UserInfo> call, Throwable t) {
        }
    });
}

And here's how you use it

Util.login("email", "password", new Util.Callback() {
   void onResponse(User info) {
       // Update UI
   }
});

Please be aware that this callback can leak memory, make sure to clean it if you leave your current activity/fragment.

edited Dec 03 '17 at 00:26

answered Dec 02 '17 at 23:47

elmorabea

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yeah, but I just want to get the return value in clickListener, otherwise I can't get it if I move it to the response block – Jinming Shi Dec 02 '17 at 23:51
But you cannot get it in the click listener, you listener onClick() method will finish execution long before you network call come back with response, what do you want to do with the response? update UI? – elmorabea Dec 02 '17 at 23:53
I just want to get the response immediately, because in the next step I will use the return value to make another request – Jinming Shi Dec 02 '17 at 23:57
Network requests take time, you can NOT get it immediately, if you to execute another request, do it on onResponse of the first one. – elmorabea Dec 02 '17 at 23:58
but I still want to make a copy of this response and update the UI – Jinming Shi Dec 03 '17 at 00:01
@JinmingShi Updated the asnwer, take a look – elmorabea Dec 03 '17 at 00:05
I'm sorry, I'm little confused about the interface, I don't know how it could solve this problem ,as I followed your code, there is some compile error – Jinming Shi Dec 03 '17 at 00:23
Sorry, I forgot the return type of the interface method, I added a usage example – elmorabea Dec 03 '17 at 00:27
it works, as you mentioned it will leak the memory, how could I clean it like you said – Jinming Shi Dec 03 '17 at 00:41
There are multiple ways, you can for example use WeakReference to hold the Callback instance – elmorabea Dec 03 '17 at 00:45
ok, thank you very much for your great help!!! – Jinming Shi Dec 03 '17 at 00:55

Android Retrofit request how to get retrofit response in main Thread

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