Android通过注解实现UI的监听器绑定

和UI控件绑定原理类似，UI和事件绑定也是通过注解Annatation和反射实现的，都是通过方法名然后使用反射的invoke方法。

1 写法一：http://www.jianshu.com/p/9bee8e143410，该方法需要实现用于注解方法的Annotation，然后对该类的方法进行扫描，从而找到具实现点击事件的方法

public class PanViewInjector {  public static void process(final Object o) {      Class c = o.getClass();      Method[] methods = c.getDeclaredMethods();      for (final Method m : methods) {          OnClick click = m.getAnnotation(OnClick.class);//通过反射api获取方法上面的注解          if (click != null) {              if (o instanceof Activity) {                  if (click.value() == -1) return;                  View view = ((Activity) o).findViewById(click.value());//通过注解的值获取View控件                  if (view == null) return;                  view.setOnClickListener(new View.OnClickListener() {                      @Override                      public void onClick(View v) {                          try {                              m.invoke(o);//通过反射来调用被注解修饰的方法                          } catch (Exception e) {                              e.printStackTrace();                          }                      }                  });              }          }      }  }}最后在Activity里面使用注解，并在Oncreate里面调用PanViewInjector.process()public class MainActivity extends AppCompatActivity {  @OnClick(R.id.centerButton)//使用注解  public void toCenter(){      Toast.makeText(this,"注解起作用啦",Toast.LENGTH_SHORT).show();  }  @Override  protected void onCreate(Bundle savedInstanceState) {      super.onCreate(savedInstanceState);      setContentView(R.layout.activity_main);      PanViewInjector.process(this);//调用注解处理器  }}

写法二：Afinal原理：https://github.com/yangfuhai/afinal/blob/master/src/net/tsz/afinal/FinalActivity.java

Afinal是通过在UI的变量名称上直接绑定的一个方法名称，与方法一相比，不用扫描整个类中的方法来找到与事件相关的方法。Afinal适用一个控件一个方法，方法一可应用于多个应用对应一个方法。

public abstract class FinalActivity extends Activity {public void setContentView(int layoutResID) {super.setContentView(layoutResID);initInjectedView(this);}public void setContentView(View view, LayoutParams params) {super.setContentView(view, params);initInjectedView(this);}public void setContentView(View view) {super.setContentView(view);initInjectedView(this);}public static void initInjectedView(Activity activity){initInjectedView(activity, activity.getWindow().getDecorView());}public static void initInjectedView(Object injectedSource,View sourceView){Field[] fields = injectedSource.getClass().getDeclaredFields();if(fields!=null && fields.length>0){for(Field field : fields){try {field.setAccessible(true);if(field.get(injectedSource)!= null )continue;ViewInject viewInject = field.getAnnotation(ViewInject.class);if(viewInject!=null){int viewId = viewInject.id();    field.set(injectedSource,sourceView.findViewById(viewId));    setListener(injectedSource,field,viewInject.click(),Method.Click);setListener(injectedSource,field,viewInject.longClick(),Method.LongClick);setListener(injectedSource,field,viewInject.itemClick(),Method.ItemClick);setListener(injectedSource,field,viewInject.itemLongClick(),Method.itemLongClick);Select select = viewInject.select();if(!TextUtils.isEmpty(select.selected())){setViewSelectListener(injectedSource,field,select.selected(),select.noSelected());}}} catch (Exception e) {e.printStackTrace();}}}}private static void setViewSelectListener(Object injectedSource,Field field,String select,String noSelect)throws Exception{Object obj = field.get(injectedSource);if(obj instanceof View){((AbsListView)obj).setOnItemSelectedListener(new EventListener(injectedSource).select(select).noSelect(noSelect));}}private static void setListener(Object injectedSource,Field field,String methodName,Method method)throws Exception{if(methodName == null || methodName.trim().length() == 0)return;Object obj = field.get(injectedSource);switch (method) {case Click:if(obj instanceof View){((View)obj).setOnClickListener(new EventListener(injectedSource).click(methodName));}break;case ItemClick:if(obj instanceof AbsListView){((AbsListView)obj).setOnItemClickListener(new EventListener(injectedSource).itemClick(methodName));}break;case LongClick:if(obj instanceof View){((View)obj).setOnLongClickListener(new EventListener(injectedSource).longClick(methodName));}break;case itemLongClick:if(obj instanceof AbsListView){((AbsListView)obj).setOnItemLongClickListener(new EventListener(injectedSource).itemLongClick(methodName));}break;default:break;}}public enum Method{Click,LongClick,ItemClick,itemLongClick}

EventListener.java

package net.tsz.afinal.annotation.view;import java.lang.reflect.Method;import net.tsz.afinal.exception.ViewException;import android.view.View;import android.view.View.OnClickListener;import android.view.View.OnLongClickListener;import android.widget.AdapterView;import android.widget.AdapterView.OnItemClickListener;import android.widget.AdapterView.OnItemLongClickListener;import android.widget.AdapterView.OnItemSelectedListener;public class EventListener implements OnClickListener, OnLongClickListener, OnItemClickListener, OnItemSelectedListener,OnItemLongClickListener {private Object handler;private String clickMethod;private String longClickMethod;private String itemClickMethod;private String itemSelectMethod;private String nothingSelectedMethod;private String itemLongClickMehtod;public EventListener(Object handler) {this.handler = handler;}public EventListener click(String method){this.clickMethod = method;return this;}public EventListener longClick(String method){this.longClickMethod = method;return this;}public EventListener itemLongClick(String method){this.itemLongClickMehtod = method;return this;}public EventListener itemClick(String method){this.itemClickMethod = method;return this;}public EventListener select(String method){this.itemSelectMethod = method;return this;}public EventListener noSelect(String method){this.nothingSelectedMethod = method;return this;}public boolean onLongClick(View v) {return invokeLongClickMethod(handler,longClickMethod,v);}public boolean onItemLongClick(AdapterView<?> arg0, View arg1, int arg2,long arg3) {return invokeItemLongClickMethod(handler,itemLongClickMehtod,arg0,arg1,arg2,arg3);}public void onItemSelected(AdapterView<?> arg0, View arg1, int arg2,long arg3) {invokeItemSelectMethod(handler,itemSelectMethod,arg0,arg1,arg2,arg3);}public void onNothingSelected(AdapterView<?> arg0) {invokeNoSelectMethod(handler,nothingSelectedMethod,arg0);}public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, long arg3) {invokeItemClickMethod(handler,itemClickMethod,arg0,arg1,arg2,arg3);}public void onClick(View v) {invokeClickMethod(handler, clickMethod, v);}private static Object invokeClickMethod(Object handler, String methodName,  Object... params){if(handler == null) return null;Method method = null;try{   method = handler.getClass().getDeclaredMethod(methodName,View.class);if(method!=null)return method.invoke(handler, params);elsethrow new ViewException("no such method:"+methodName);}catch(Exception e){e.printStackTrace();}return null;}private static boolean invokeLongClickMethod(Object handler, String methodName,  Object... params){if(handler == null) return false;Method method = null;try{   //public boolean onLongClick(View v)method = handler.getClass().getDeclaredMethod(methodName,View.class);if(method!=null){Object obj = method.invoke(handler, params);return obj==null?false:Boolean.valueOf(obj.toString());}elsethrow new ViewException("no such method:"+methodName);}catch(Exception e){e.printStackTrace();}return false;}private static Object invokeItemClickMethod(Object handler, String methodName,  Object... params){if(handler == null) return null;Method method = null;try{   ///onItemClick(AdapterView<?> arg0, View arg1, int arg2, long arg3)method = handler.getClass().getDeclaredMethod(methodName,AdapterView.class,View.class,int.class,long.class);if(method!=null)return method.invoke(handler, params);elsethrow new ViewException("no such method:"+methodName);}catch(Exception e){e.printStackTrace();}return null;}private static boolean invokeItemLongClickMethod(Object handler, String methodName,  Object... params){if(handler == null) throw new ViewException("invokeItemLongClickMethod: handler is null :");Method method = null;try{   ///onItemLongClick(AdapterView<?> arg0, View arg1, int arg2,long arg3)method = handler.getClass().getDeclaredMethod(methodName,AdapterView.class,View.class,int.class,long.class);if(method!=null){Object obj = method.invoke(handler, params);return Boolean.valueOf(obj==null?false:Boolean.valueOf(obj.toString()));}elsethrow new ViewException("no such method:"+methodName);}catch(Exception e){e.printStackTrace();}return false;}private static Object invokeItemSelectMethod(Object handler, String methodName,  Object... params){if(handler == null) return null;Method method = null;try{   ///onItemSelected(AdapterView<?> arg0, View arg1, int arg2,long arg3)method = handler.getClass().getDeclaredMethod(methodName,AdapterView.class,View.class,int.class,long.class);if(method!=null)return method.invoke(handler, params);elsethrow new ViewException("no such method:"+methodName);}catch(Exception e){e.printStackTrace();}return null;}private static Object invokeNoSelectMethod(Object handler, String methodName,  Object... params){if(handler == null) return null;Method method = null;try{   //onNothingSelected(AdapterView<?> arg0)method = handler.getClass().getDeclaredMethod(methodName,AdapterView.class);if(method!=null)return method.invoke(handler, params);elsethrow new ViewException("no such method:"+methodName);}catch(Exception e){e.printStackTrace();}return null;}}