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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);	
			else
				throw 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());	
			}
			else
				throw 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);	
			else
				throw 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()));	
			}
			else
				throw 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);	
			else
				throw 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);	
			else
				throw new ViewException("no such method:"+methodName);
		}catch(Exception e){
			e.printStackTrace();
		}
		
		return null;
	}

}
Android UI android 提高 注解 绑定事件
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