通过反射将值设置为java类？

Question

I have this model :

public class Base_RegisterPlack {


    private String RegisterPlackTypeValue;

    public void setRegisterPlackTypeValue(String registerPlackTypeValue) {
        RegisterPlackTypeValue = registerPlackTypeValue;
    }
}

in this method i pass this object:

gridView2.setAdapter(GridHelper.getRegisterPlackAdapter(getContext(), getCookie(),
        result_getClsBase_Info.getBase_RegisterPlack()), Base_RegisterPlack.class);

body of setAdapter method is:

public void setAdapter (DataGridAdapter adapter, Class cls) {
    this.baseClass = cls;
    super.setAdapter(adapter);
    setGridAdapter(adapter);
}

Now i want to call set method setRegisterPlackTypeValue so i write this reflection :

try {
    Field field = baseClass.getDeclaredField("RegisterPlackTypeValue");
    field.setAccessible(true);
    field.set(baseClass,"test");
} catch (NoSuchFieldException e) {
    e.printStackTrace();
} catch (IllegalAccessException e) {
    e.printStackTrace();
}

I got this error :

java.lang.IllegalArgumentException: Expected receiver of type com.module.contracts.Base_RegisterPlack, but got java.lang.Class<com.module.contracts.Base_RegisterPlack>

How can i call set method and convert again this baseClass to the Base_RegisterPlack after set value to it?

Answer 1

You will need an instance of the class that baseClass represents. How to do this exactly will depend on the design of the actual baseClass (ie, whether it has constructors or static factory methods), and what arguments these needs. In the simplest case, your base class will have a parameterless constructor, and you can simply do:

field.set(baseClass.newInstance(),"test");

However, you will probably want to retain a reference to whatever instance is returned by newInstance .

It's important to remember that with reflection an instance of type Field represents a field declaration in its declaring class, and not an actual field (instance variable) in an object. Thus, the value stored in variable field in your code is not related to any instance. This is why when you call Field.set(target, value) you have to supply an object of class baseClass . The field of that object, which is represented by field , will be set to value "test" . See this tutorial for details.