如何在Kotlin中实现java SAM接口？

Question

In Java it is possible to write code like this:

model.getObservableProduct().observe(this, new Observer<ProductEntity>() {
    @Override
    public void onChanged(@Nullable ProductEntity productEntity) {
        model.setProduct(productEntity);
    }
});

However trying to override local function in Kotlin results in:

---

Question: is it possible to override local function in Kotlin?

Answer 1

try using object expression instead.

//       the parentheses must be removed if Observer is an interface  ---V
model.getObservableProduct().observe(this, object:Observer<ProductEntity>(){
   override fun onChanged(productEntity:ProductEntity?) {
      model.setProduct(productEntity);
   }
});

IF the Observer is a java SAM interface ( kotlin SAM interfaces aren't currently supported ) then you can using lambda expression instead as further:

model.getObservableProduct().observe(this, Observer<ProductEntity>{
      model.setProduct(it);
});

OR using a lambda expression instead, for example:

// specify the lambda parameter type ---v
model.getObservableProduct().observe<ProductEntity>(this) {
      model.setProduct(it);
};