如何创建实现通用接口的全局通用类？

Question

To be very honest I need to use Retofit Callback for multiple classes. I dont want to write the callback interface with onResponse and onFailour method in each UI page.

So I decided to write a global class which will implements the Retrofit Callback interface.

But my problem is, I want to make it Generic, because there are many different ResponseParser classes which are going to use this global class.

I tried like below, but facing a little problem in it.

public class WebAPIControler implements Callback<TResponse>{

@Override
public void onResponse(Call<TResponse> call, Response<TResponse> response) {

}

@Override
public void onFailure(Call<TResponse> call, Throwable t) {

}
}

Here compiler not able to found TResponse class. here TResponse is a generic class where I want to handle all king of ResponseParser classes. So I give a name it as T or TResponse. Please help me how to handle this.

Answer 1

You have to make your class as generic class first then implement generic interface.

public class WebAPIControler implements Callback<T>{

@Override
public void onResponse(Call<T> call, Response<T> response) {

}

@Override
public void onFailure(Call<T> call, Throwable t) {

}
}

What is T?

E - Element (used extensively by the Java Collections Framework)
K - Key
N - Number
T - Type
V - Value
S,U,V etc. - 2nd, 3rd, 4th types

Source

I suggest you just implement generic interface, your class is not required to be generic.

UPDATE

a.create Interface

interface CustomSubscriber<T>  {
void test(T object);
}

b.Implement your interface with any object

public class WebAPIControler implements CustomSubscriber<JsonObject>{

@Override
public void test(JsonObject object) {

}
}

Answer 2

As others have commented, what you're missing is the generic type declaration in public class WebAPIControler<T> . That's why the compiler is complaining T doesn't exist.

public class WebAPIControler<T> implements Callback<T> {
    @Override
    public void onResponse(Call<T> call, Response<T> response) {

    }

    @Override
    public void onFailure(Call<T> call, Throwable t) {

    }
}