I have a json with class name, something like this:
{
"view_class" : "com.view.MyClass"
}
And I have this hierarchy:
public class Config {
public String viewClass;
...
}
public interface ViewHolderInterface {
void bindValue(...);
}
public class SuperMyClass extends RecyclerView.ViewHolder
implements ViewHolderInterface {
...
}
public class MyClass extends SuperMyClass {
...
}
I read a json file and I generate a "Config" object, so the idea is this:
public void bindViewHolder(SuperMyClass holder, Config config) {
Class viewHolderClass;
try {
//row.viewHolderClass = "com.view.MyClass"
viewHolderClass = Class.forName(config.viewClass);
} catch (final Exception exception) {
}
// Here I need to "cast" a holder to MyClass and execute the method bindValue.
final ViewHolderInterface viewHolderInstance =
(ViewHolderInterface) viewHolderClass.cast(holder);
viewHolderInstance.bindObjectValue(...);
}
I have tried to do this cast using reflection but I this throws an exception:
java.lang.ClassCastException: SuperMyClass cannot be cast to MyClass
I think that my error is using reflection and the same time try to up-cast, but I have not found another way to do this.
Consider that there may be more than one "view_class" type (remember that this class is an implementation of a ViewHolder).
Any idea?
I think that my error is using reflection and the same time try to up-cast, but I have not found another way to do this.
Your reflection is ok, but the downcasting is not. Take a look at this question: explicit casting from super class to subclass
Consider that there may be more than one "view_class" type (remember that this class is an implementation of a ViewHolder).
You can inspect the object instance in runtime to find out its class. You need not tell the class by outside means.
You can try a safer approach like:
// mind the comparison order from subclass upward
if (MyClass.class.isInstance(holder)) {
MyClass myClassHolder = (MyClass) holder;
} else if (SuperMyClass.class.isInstance(holder)) {
SuperMyClass superMyClassHolder = (SuperMyClass) holder;
} else if (ViewHolder.class.isInstance(holder)) {
ViewHolder viewHolder = (ViewHolder) holder;
}