Generate a field as anonymous class with JavaPoet

Question

I'm working on an annotation processor library and I'm using JavaPoet to generate som Java code. I need to generate a class with a field declared with an anonymous class like the following code:

public class Dummy {
    private final OnSharedPreferenceChangeListener valueFloatListener = new OnSharedPreferenceChangeListener() {

        @Override
        public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key) {
            switch (key) {
            case "value_float":
                valueFloatSubject.onNext(sharedPreferences.getFloat(key, defaultBean.valueFloat));
                break;
            }

        }
    };  
}

How can I define valueFloatListener field with JavaPoet? Tnx in advance.

score 2 · Accepted Answer · answered Jun 01 '18 at 14:46

You have to use TypeSpec.anonymousClassBuilder("").

Something like this should work:

MethodSpec.Builder method = 
    MethodSpec.methodBuilder("onSharedPreferenceChangeListener")
              .addAnnotation(Override.class)
              .addModifiers(Modifier.PUBLIC, 
                            Modifier.FINAL)  
              .addParameter(ParameterSpec.builder(ClassName.get(SharedPreferences.class),
                                                                "sharedPreferences")
                                         .build())
              .addParameter(ParameterSpec.builder(ClassName.get(String.class), 
                                                  "key")
                                         .build())
              .addCode(" add the switch-statement here ...");

TypeSpec.Builder typeSpec = 
    TypeSpec.classBuilder("Dummy")
            .addModifiers(Modifier.PUBLIC)
            .addStatement("private final $T valueFloatListener = new $T() $L",
                          ClassName.get(OnSharedPreferenceChangeListener.class),
                          ClassName.get(OnSharedPreferenceChangeListener.class), 
                          TypeSpec.anonymousClassBuilder("")
                                  .addSuperinterface(ClassName.get(OnSharedPreferenceChangeListener.class))
                                  .addMethod(method.build())
                                  .build());

Not sure if the code is compile clean, but I think it shows, how to solve the problem.

Generate a field as anonymous class with JavaPoet

1 Answers1