Android 反射注解与动态代理综合使用详解

public enum RetentionPolicy {
/**
 * Annotations are to be discarded by the compiler.
 */
 SOURCE,

/**
 * Annotations are to be recorded in the class file by the compiler
 * but need not be retained by the VM at run time. This is the default
 * behavior.
 */
 CLASS,

/**
 * Annotations are to be recorded in the class file by the compiler and
 * retained by the VM at run time, so they may be read reflectively.
 *
 * @see java.lang.reflect.AnnotatedElement
 */
 RUNTIME
 }

public enum ElementType {
/** Class, interface (including annotation type), or enum declaration */
TYPE,

/** Field declaration (includes enum constants) */
FIELD,

/** Method declaration */
METHOD,

/** Formal parameter declaration */
PARAMETER,

/** Constructor declaration */
CONSTRUCTOR,

/** Local variable declaration */
LOCAL_VARIABLE,

/** Annotation type declaration */
ANNOTATION_TYPE,

/** Package declaration */
PACKAGE,

/**
 * Type parameter declaration
 *
 * @since 1.8
 * @hide 1.8
 */
TYPE_PARAMETER,

/**
 * Use of a type
 *
 * @since 1.8
 * @hide 1.8
 */
TYPE_USE
}

@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
 public @interface InjectView {
 int value();
}

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@EventType(listenerType = View.OnClickListener.class, listenerSetter = "setOnClickListener", methodName 
 = "onClick")
 public @interface onClick {
 int[] value();
} 

@Target(ElementType.ANNOTATION_TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface EventType {
Class listenerType();
String listenerSetter();
String methodName();
}

@InjectView(R.id.bind_view_btn)
 Button mBindView;

public static void injectView(Activity activity) {
 if (null == activity) return;

 Class<? extends Activity> activityClass = activity.getClass();
 Field[] declaredFields = activityClass.getDeclaredFields();
 for (Field field : declaredFields) {
  if (field.isAnnotationPresent(InjectView.class)) {
   //解析InjectView 获取button id
   InjectView annotation = field.getAnnotation(InjectView.class);
   int value = annotation.value();

   try {
    //找到findViewById方法
    Method findViewByIdMethod = activityClass.getMethod("findViewById", int.class);
    findViewByIdMethod.setAccessible(true);
    findViewByIdMethod.invoke(activity, value);

   } catch (NoSuchMethodException e) {
    e.printStackTrace();
   } catch (InvocationTargetException e) {
    e.printStackTrace();
   } catch (IllegalAccessException e) {
    e.printStackTrace();
   }
  }
 }

}

@onClick({R.id.btn_bind_click, R.id.btn_bind_view})
public void invokeClick(View view) {
 switch (view.getId()) {
  case R.id.btn_bind_click:
   Log.i(Utils.TAG, "bind_click_btn Click");
   Toast.makeText(MainActivity.this,"button onClick",Toast.LENGTH_SHORT).show();
   break;
  case R.id.btn_bind_view:
   Log.i(Utils.TAG, "bind_view_btn Click");
   Toast.makeText(MainActivity.this,"button binded",Toast.LENGTH_SHORT).show();
   break;
 }
}

public static void injectEvent(Activity activity) {
 if (null == activity) {
  return;
 }
 Class<? extends Activity> activityClass = activity.getClass();
 Method[] declaredMethods = activityClass.getDeclaredMethods();

 for (Method method : declaredMethods) {
  if (method.isAnnotationPresent(onClick.class)) {
   Log.i(Utils.TAG, method.getName());
   onClick annotation = method.getAnnotation(onClick.class);
   //get button id
   int[] value = annotation.value();
   //get EventType
   EventType eventType = annotation.annotationType().getAnnotation(EventType.class);
   Class listenerType = eventType.listenerType();
   String listenerSetter = eventType.listenerSetter();
   String methodName = eventType.methodName();

   //创建InvocationHandler和动态代理(代理要实现listenerType，这个例子就是处理onClick点击事件)
   ProxyHandler proxyHandler = new ProxyHandler(activity);
   Object listener = Proxy.newProxyInstance(listenerType.getClassLoader(), new Class[]{listenerType}, proxyHandler);

   proxyHandler.mapMethod(methodName, method);
   try {
    for (int id : value) {
     //找到Button
     Method findViewByIdMethod = activityClass.getMethod("findViewById", int.class);
     findViewByIdMethod.setAccessible(true);
     View btn = (View) findViewByIdMethod.invoke(activity, id);
     //根据listenerSetter方法名和listenerType方法参数找到method
     Method listenerSetMethod = btn.getClass().getMethod(listenerSetter, listenerType);
     listenerSetMethod.setAccessible(true);
     listenerSetMethod.invoke(btn, listener);
    }

   } catch (NoSuchMethodException e) {
    e.printStackTrace();
   } catch (InvocationTargetException e) {
    e.printStackTrace();
   } catch (IllegalAccessException e) {
    e.printStackTrace();
   }
  }
 }
}

@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
 Log.i(Utils.TAG, "method name = " + method.getName() + " and args = " + Arrays.toString(args));
 Object handler = mHandlerRef.get();
 if (null == handler) return null;
 String name = method.getName();
 //将onClick方法的调用映射到activity 中的invokeClick()方法
 Method realMethod = mMethodHashMap.get(name);
 if (null != realMethod){
  return realMethod.invoke(handler, args);
 }
 return null;
}