如activityA代码：
activityB = new ActivtyB(mHandler,CLOSE_SEARCH_MSG);
//新建对像B传递，一个handler和Message，然后在activityB中发送即可触发activityA的方法：
activityB代码：
if (mHandler != null) {
Message msg = new Message();
msg.what = CLOSE_SEARCH_MSG;
mHandler.sendMessage(msg);
}
activityA代码：
private Handler mHandler = new Handler(){
public void handleMessage(Message msg){
switch (msg.what){
case CLOSE_SEARCH_MSG:
//收到消息做相应事件
break;
}
}
};