Apply variable to Retrofit HTTP method annotation

Question

This is the code. I want put params EMAIL! But i get attribute value must be costant

public interface Api{
    Context context=null;
    SharedPreferences sharedPref = context.getSharedPreferences("login",Context.MODE_PRIVATE);
    static String email = sharedPref.getString("email","");

    @GET("Home.php?email="+email+"&")
    Call<List<Variabili_Main>> getHome(@Query("page") int index);

}

Help me!

ok i have edit but now how edit this? And here what i do?

private void load(int index){
    Call<List<Variabili_Main>> call = api.getHome(index);
    call.enqueue(new Callback<List<Variabili_Main>>() {
        @Override
        public void onResponse(Call<List<Variabili_Main>> call, Response<List<Variabili_Main>> response) {
            if(response.isSuccessful()){
                movies.addAll(response.body());
                adapter.notifyDataChanged();
            }else{
                Log.e(TAG," Response Error "+String.valueOf(response.code()));
            }
        }

        @Override
        public void onFailure(Call<List<Variabili_Main>> call, Throwable t) {
            Log.e(TAG," Response Error "+t.getMessage());
        }
    });
}

I want put email shared preference in @GET but i get attribute value must be costant — Noe Nazza, Oct 17 '16 at 23:10
As the email is loaded from the shared preferences static final is not possible. Nonetheless java annotations can only be given values which are constant expressions (see JLS 9.7.1), enum values or some times class literals. So you can't use a dynamially generated string for an annotation as ist must be known at compile time. I'm not sure about your goal, though. — Tropid, Oct 17 '16 at 23:11
Possible duplicate of [Get rid of "The value for annotation attribute must be a constant expression" message](http://stackoverflow.com/questions/16509065/get-rid-of-the-value-for-annotation-attribute-must-be-a-constant-expression-me) — Andrew Li, Oct 17 '16 at 23:12
Understandable... but primarily this won't work. You can't get the context or sharedprefereces within an interface — OneCricketeer, Oct 17 '16 at 23:18
@Hala.m i have try your solution, but now i get error in main activity see above — Noe Nazza, Oct 17 '16 at 23:26
"get error" doesn't mean much without actually saying **what** error — OneCricketeer, Oct 17 '16 at 23:29
function load() must have 2 arguments but now have one and i get error, because i have int and string... — Noe Nazza, Oct 17 '16 at 23:31

score 3 · Answer 1 · edited May 23 '17 at 10:32

After rereading the question @cricket_007 was correct since the email was to be sent as a query

I'll update it for future reference to have both answers

I think this is how it should be I has similar issue with header before

try this solution

this is if the email is in the path itself not a query

@GET("Home.php/{email}")
Call<List<Variabili_Main>> getHome(@Path("email") String email,@Query("page") int index);

this is to send it as a query

@GET("Home.php")
Call<List<Variabili_Main>> getHome(@Query("email") String email,@Query("page") int index);

to call you need to add the email in your call

 SharedPreferences sharedPref = context.getSharedPreferences("login",Context.MODE_PRIVATE);
static String email = sharedPref.getString("email","");
api.getHome(email,index)

check for more details Dynamic Paths in Retrofit and https://square.github.io/retrofit/

private void load(int index){ Call> call = api.getHome(index); call.enqueue(new Callback>() { @Override public void onResponse(Call> call, Response> response) { — Noe Nazza, Oct 17 '16 at 23:22

OneCricketeer · Accepted Answer · 2016-10-17T23:28:22.697

If you want to concatenate a string in the annotation, it must be a compile-time constant. Something that is received at run-time from SharedPreferences isn't constant.

Probably better to add it as a query parameter.

@GET("Home.php")
Call<List<Variabili_Main>> getHome(@Query("email") String email, @Query("page") int index);

Then, just pass the email when you actually need it.

private void load(int index){

    // TODO: getContext ... shared preferences... 
    String email = prefs.getString("email");
    Call<List<Variabili_Main>> call = api.getHome(email, index);

    call.enqueue(new Callback<List<Variabili_Main>>() {
        @Override
        public void onResponse(Call<List<Variabili_Main>> call, Response<List<Variabili_Main>> response) {
            if(response.isSuccessful()){
                movies.addAll(response.body());
                adapter.notifyDataChanged();
            }else{
                Log.e(TAG," Response Error "+String.valueOf(response.code()));
            }
        }

        @Override
        public void onFailure(Call<List<Variabili_Main>> call, Throwable t) {
            Log.e(TAG," Response Error "+t.getMessage());
        }
    });
}

Tropid · Answer 3 · 2016-10-17T23:30:28.213

As stated in your comments your goal is to handle a HTTP GET request to a specific route where the email query parameter is determined at runtime (loaded from shared preferences).

To achieve this goal you should use the @Query notation provided by the retrofit library.

Example from https://square.github.io/retrofit/ "API Declaration"

@GET("group/{id}/users")
Call<List<User>> groupList(@Path("id") int groupId, @Query("sort") String sort);

In your case you can pass the email value as argument to your handler function and continue from there. E.g.

@GET("Home.php")
Call<List<Variabili_Main>> getHome(@Query("page") int index, @Query("email") String email);

Why it is not possible to provide the email in the annotation:

As stated in my comment providing runtime strings to annotations is not possible as stated in the JLS 9.7.1:

If T is a primitive type or String, and V is a constant expression
(§15.28).
V is not null.
If T is Class, or an invocation of Class, and V is a class literal (§15.8.2).
If T is an enum type, and V is an enum constant.

Where V is the value inside the annotation.

thanks for reply, now i get error in main activity funciton see above — Noe Nazza, Oct 17 '16 at 23:29

Apply variable to Retrofit HTTP method annotation

3 Answers3