树叶云鸿蒙OS教程：鸿蒙OS NFC消息通知

场景介绍

NFC 消息通知（Notification）是 HarmonyOS 内部或者与应用之间跨进程通讯的机制，注册者在注册消息通知后，一旦符合条件的消息被发出，注册者即可接收到该消息。

接口说明

注册并获取 NFC 状态改变消息

1. 构建消息通知接收者 NfcStateEventSubscriber。

1. 注册 NFC 状态改变消息。

1. NfcStateEventSubscriber 接收并处理 NFC 状态改变消息。

   // 构建消息接收者/注册者
   class NfcStateEventSubscriber extends CommonEventSubscriber {
       NfcStateEventSubscriber (CommonEventSubscribeInfo info) {
           super(info);
       }

    
       @Override
       public void onReceiveEvent(CommonEventData commonEventData) {
           if (commonEventData == null || commonEventData.getIntent() == null) {
               return;
           }
           if (NfcController.STATE_CHANGED.equals(commonEventData.getIntent().getAction())) {
               IntentParams params = commonEventData.getIntent().getParams();
               if (params != null) {
                   int currState = commonEventData.getIntent().getIntParam(NfcController.EXTRA_NFC_STATE, NfcController.STATE_OFF);
               }
           }
       }
   }

    
   // 注册消息
   MatchingSkills matchingSkills = new MatchingSkills();
   // 增加获取 NFC 状态改变消息
   matchingSkills.addEvent(NfcController.STATE_CHANGED);
   matchingSkills.addEvent(CommonEventSupport.COMMON_EVENT_NFC_ACTION_ADAPTER_STATE_CHANGED);
   CommonEventSubscribeInfo subscribeInfo = new CommonEventSubscribeInfo(matchingSkills);
   NfcStateEventSubscriber subscriber = new NfcStateEventSubscriber(subscribeInfo);
   try {
       CommonEventManager.subscribeCommonEvent(subscriber);
   } catch (RemoteException e) {
       HiLog.e(TAG, "doSubscribe occur exception:" + e.toString());
   }

注册并获取 NFC 场强消息

1. 构建消息通知接收者NfcFieldOnAndOffEventSubscriber。

1. 注册 NFC 场强消息。

1. NfcFieldOnAndOffEventSubscriber 接收并处理 NFC 场强消息。

   // 构建消息接收者/注册者
   class NfcFieldOnAndOffEventSubscriber extends CommonEventSubscriber {
       NfcFieldOnAndOffEventSubscriber (CommonEventSubscribeInfo info) {
           super(info);
       }

    
       @Override
       public void onReceiveEvent(CommonEventData commonEventData) {
           if (commonEventData == null || commonEventData.getIntent() == null) {
               return;
           }
           if (NfcController.FIELD_ON_DETECTED.equals(commonEventData.getIntent().getAction())) {
               IntentParams params = commonEventData.getIntent().getParams();
               if (params == null) {
                   HiLog.i(TAG, "Pure FIELD_ON_DETECTED");
               } else {
                   HiLog.i(TAG, "Transaction FIELD_ON_DETECTED");  
                   Intent transactionIntent = (Intent) params.getParam("transactionIntent");
               }
           } else if (NfcController.FIELD_OFF_DETECTED.equals(commonEventData.getIntent().getAction())) {
               HiLog.i(TAG, "FIELD_OFF_DETECTED");
           }
           HiLog.i(TAG, "MyFieldOnAndOffEventSubscriber onReceiveEvent ....:" + commonEventData.getIntent().getAction());
       }
   }

    
   // 注册消息
   MatchingSkills matchingSkills = new MatchingSkills();
   // 增加获取 NFC 状态改变消息
   matchingSkills.addEvent(NfcController.FIELD_ON_DETECTED);
   matchingSkills.addEvent(NfcController.FIELD_OFF_DETECTED);
   CommonEventSubscribeInfo subscribeInfo = new CommonEventSubscribeInfo(DomainMode.BOTH, matchingSkills);
   HiLog.i(TAG, "subscribeInfo permission: " + subscribeInfo.getPermission());
   MyFieldOnAndOffEventSubscriber subscriber = new MyFieldOnAndOffEventSubscriber(subscribeInfo);
   try {
       CommonEventManager.subscribeCommonEvent(subscriber);
   } catch (RemoteException e) {
       HiLog.e(TAG, "doSubscribe occur exception:" + e.toString());
   }