如何使用反射实现回调？

Question

I have this constructor in a jar:

public ClientListFragment(String[] values, OnActionListener onActionListener)
{
    this.values = values;
    this.setOnActionListener(onActionListener);
}

This is the implementation of the abstract class OnActionListener:

public abstract class OnActionListener {

    public abstract void onAction(int actonId);
}

In the main project, create an instance of this class, which is in a jar:

 final String libPath = Environment.getExternalStorageDirectory() + "/myapi.jar";
           final File tmpDir = new File(libPath);

           final DexClassLoader classloader = new DexClassLoader(libPath, tmpDir.getAbsolutePath(), null, this.getClass().getClassLoader());
           final Class<Object> classToLoad = (Class<Object>) classloader.loadClass("com.api.fragment.ClientListFragment");


//In this constructor, we inform an array of String and not know how to pass the callback of the abstract class
           Constructor constructor = classToLoad.getConstructor(new Class[]{String[].class});

//get a instance
           Object fragmentListClients = constructor.newInstance(items);

My question is: How do I report a callback to a loaded class via reflection in Java? Ie how:

onActionListener = new OnActionListener() {
            @Override
            public void onAction(int actonId) {

            }
        };

Answer 1

    Method onAction = classToLoad.getDeclaredMethod("onAction", int.class);
    onAction.invoke(fragmentListClients, 1);

Where fragmentListClients is the target object 1 is your actionId. You're using reflection to get a reference to the Method and invoking it.

You'd probably be better off creating an interface and using inheritance to implement and call your onAction method as that gets you type safety and avoids reflection for the method call which can be inefficient.

Answer 2

You must use Dynamic proxies to implement interfaces at run-time Please go through this link for more Info. http://tutorials.jenkov.com/java-reflection/dynamic-proxies.html