android - 如何在 Kotlin 中制作双向转换器？ (在java中工作)

Question

我收到这个错误:

Error:(32, 50) cannot find method indexFromModel(android.databinding.ObservableList<br.com.martinlabs.usecase.model.GrupoDoPrincipal>, br.com.martinlabs.usecase.model.GrupoDoPrincipal) in class br.com.martinlabs.usecase.viewtools.Converters

但是我在 Converters 上有这个方法:(我也试过一个里面有伴随对象的类)

object Converters {

    fun indexFromModel(list: ObservableList<GrupoDoPrincipal>, model: GrupoDoPrincipal): Int {
        return list.indexOfFirst { it?.id == model?.id }
    }

    @InverseMethod("indexFromModel")
    fun indexToModel(list: ObservableList<GrupoDoPrincipal>, index: Int): GrupoDoPrincipal {
        return index.let { list[it] }
    }

}

用法:

<Spinner
    android:selectedItemPosition="@={Converters.indexFromModel(vm.allGrupoDoPrincipal, vm.principal.grupoDoPrincipal)}"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"/>

---

此方法适用于 Java:

public static int indexFromModel(ObservableList<GrupoDoPrincipal> list, GrupoDoPrincipal model) {
    for (int i = 0; i < list.size(); i++) {
        if (list.get(i).getId() == model.getId()) {
            return i;
        }
    }

    return -1;
}

@InverseMethod("indexFromModel")
public static GrupoDoPrincipal indexToModel(ObservableList<GrupoDoPrincipal> list, int index) {
    return list.get(index);
}

Answer 1

在 Kotlin 中，object 方法不是真正的static。要使其成为静态，您需要为此方法添加注释 @JvmStatic:

object Converters {

    @JvmStatic
    fun indexFromModel(list: ObservableList<GrupoDoPrincipal>, model: GrupoDoPrincipal): Int {
        return list.indexOfFirst { it?.id == model?.id }
    }

    @JvmStatic
    @InverseMethod("indexFromModel")
    fun indexToModel(list: ObservableList<GrupoDoPrincipal>, index: Int): GrupoDoPrincipal {
        return index.let { list[it] }
    }
}