在工作和生活中，遇见新的同事或者合作伙伴，交换名片是一个常见的用户需求，纸质名片常忘带、易丢失，是客户的一个痛点。因此，市场上出现了很多交换电子名片的APP和小程序。那么，如何给自己的APP开发一个名片交换功能呢？

我们可以接入华为近距离通信服务，通过近距离设备间消息订阅（Nearby Message），快速实现一对一或一对多名片交换。下图是功能演示：

开发具体步骤如下：

1. 开发准备

如果您已经是华为的开发者，可以省略此步骤。如果您以前没有集成华为移动服务的经验，那么需要先配置AppGallery Connect，开通近距离通信服务并集成HMS SDK。相关步骤请参考官方文档。

2. 添加权限

在使用Nearby Message之前，需要添加网络权限、蓝牙权限、位置权限。在工程的AndroidManifest.xml文件中添加如下权限：

<uses-permission android:name="android.permission.INTERNET " />
 <uses-permission android:name="android.permission.BLUETOOTH" />
 <uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
 <!-- The location permission is also required in Android 6.0 or later. -->
 <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
 <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

3. 代码开发

3.1 动态权限申请

检查蓝牙开关、位置开关是否打开、网络是否可用，并对位置权限进行动态权限申请

@Override
 public void onStart() {
     super.onStart();
     getActivity().getApplication().registerActivityLifecycleCallbacks(this);
     checkPermission();
 }
 
 @Override
 public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
     for (int i = 0; i < permissions.length; ++i) {
         if (grantResults[i] != 0) {
             showWarnDialog(Constants.LOCATION_ERROR);
         }
     }
 }
 
 private void checkPermission() {
     if (!BluetoothCheckUtil.isBlueEnabled()) {
         showWarnDialog(Constants.BLUETOOTH_ERROR);
         return;
     }
 
     if (!LocationCheckUtil.isLocationEnabled(this.getActivity())) {
         showWarnDialog(Constants.LOCATION_SWITCH_ERROR);
         return;
     }
 
     if (!NetCheckUtil.isNetworkAvailable(this.getActivity())) {
         showWarnDialog(Constants.NETWORK_ERROR);
         return;
     }
 
     String[] deniedPermission = PermissionUtil.getDeniedPermissions(this.getActivity(), new String[] {
             Manifest.permission.ACCESS_COARSE_LOCATION,
             Manifest.permission.ACCESS_FINE_LOCATION
     });
     if (deniedPermission.length > 0) {
         PermissionUtil.requestPermissions(this.getActivity(), deniedPermission, 10);
     }
 }

3.2 封装名片发布接口和名片订阅接口

订阅到的名片消息（onFound），把名片添加到查找名片对话框中显示；名片消息丢失时（onLost），从查找名片对话框中删除该名片

private MessageHandler mMessageHandler = new MessageHandler() {
     @Override
     public void onFound(Message message) {
         CardInfo cardInfo = JsonUtils.json2Object(new String(message.getContent(), Charset.forName("UTF-8")),
                 CardInfo.class);
         if (cardInfo == null) {
             return;
         }
 
         mSearchCardDialogFragment.addCardInfo(cardInfo);
     }
 
     @Override
     public void onLost(Message message) {
         CardInfo cardInfo = JsonUtils.json2Object(new String(message.getContent(), Charset.forName("UTF-8")),
                 CardInfo.class);
         if (cardInfo == null) {
             return;
         }
 
         mSearchCardDialogFragment.removeCardInfo(cardInfo);
     }
 };
 
 private void publish(String namespace, String type, int ttlSeconds, OnCompleteListener<Void> listener) {
     Message message = new Message(JsonUtils.object2Json(mCardInfo).getBytes(Charset.forName("UTF-8")), type,
             namespace);
     Policy policy = new Policy.Builder().setTtlSeconds(ttlSeconds).build();
     PutOption option = new PutOption.Builder().setPolicy(policy).build();
     Nearby.getMessageEngine(getActivity()).put(message, option).addOnCompleteListener(listener);
 }
 
 private void subscribe(String namespace, String type, int ttlSeconds, OnCompleteListener<Void> listener,
                        GetCallback callback) {
     Policy policy = new Policy.Builder().setTtlSeconds(ttlSeconds).build();
     MessagePicker picker = new MessagePicker.Builder().includeNamespaceType(namespace, type).build();
     GetOption.Builder builder = new GetOption.Builder().setPolicy(policy).setPicker(picker);
     if (callback != null) {
         builder.setCallback(callback);
     }
     Nearby.getMessageEngine(getActivity()).get(mMessageHandler, builder.build()).addOnCompleteListener(listener);
 }

3.3  名片交换菜单处理

面对面交换名片交换码，发布个人名片成功后，订阅名片消息

private boolean onExchangeItemSelected() {
     PinCodeDialogFragment dialogFragment = new PinCodeDialogFragment(passwrod -> {
         MyCardFragment.this.publish(passwrod, passwrod, Policy.POLICY_TTL_SECONDS_MAX, result -> {
             if (!result.isSuccessful()) {
                 String str = "Exchange card fail, because publish my card fail. exception: "
                         + result.getException().getMessage();
                 Log.e(TAG, str);
                 Toast.makeText(getActivity(), str, Toast.LENGTH_LONG).show();
                 return;
             }
             MyCardFragment.this.subscribe(passwrod, passwrod, Policy.POLICY_TTL_SECONDS_INFINITE, ret -> {
                 if (!ret.isSuccessful()) {
                     MyCardFragment.this.unpublish(passwrod, passwrod, task -> {
                         String str = "Exchange card fail, because subscribe is fail, exception("
                                 + ret.getException().getMessage() + ")";
                         if (!task.isSuccessful()) {
                             str = str + " and unpublish fail, exception(" + task.getException().getMessage()
                                     + ")";
                         }
 
                         Log.e(TAG, str);
                         Toast.makeText(getActivity(), str, Toast.LENGTH_LONG).show();
                     });
                     return;
                 }
                 mSearchCardDialogFragment.setOnCloseListener(() -> {
                     MyCardFragment.this.unpublish(passwrod, passwrod, task -> {
                         if (!task.isSuccessful()) {
                             Toast.makeText(getActivity(), "Unpublish my card fail, exception: "
                                     + task.getException().getMessage(), Toast.LENGTH_LONG).show();
                         }
                     });
                     MyCardFragment.this.unsubscribe(task -> {
                         if (!task.isSuccessful()) {
                             Toast.makeText(getActivity(), "Unsubscribe fail, exception: "
                                     + task.getException().getMessage(), Toast.LENGTH_LONG).show();
                         }
                     });
                 });
                 mSearchCardDialogFragment.show(getParentFragmentManager(), "Search Card");
             }, null);
         });
     });
     dialogFragment.show(getParentFragmentManager(), "pin code");
 
     return true;
 }

3.4  收藏名片处理

收藏名片时把名片加入收藏列表，名片取消收藏时把名片从参数列表中删除，并把数据保存到本地存储中。

@Override
 public void onFavorite(CardInfo cardInfo, boolean isFavorite) {
     if (isFavorite) {
         mFavoriteMap.put(cardInfo.getId(), cardInfo);
     } else {
         mFavoriteMap.remove(cardInfo.getId());
     }
     Set<String> set = new HashSet<>(mFavoriteMap.size());
     for (CardInfo card : mFavoriteMap.values()) {
         set.add(JsonUtils.object2Json(card));
     }
     SharedPreferences sharedPreferences = getContext().getSharedPreferences("data", Context.MODE_PRIVATE);
     sharedPreferences.edit().putStringSet(Constants.MY_FAVORITES_KEY, set).apply();
 }

本次给大家演示的demo用到了华为HMS Nearby service的近距离设备间消息订阅功能。基于Nearby Message能力不仅仅可以用来做面对面交换名片，还可以帮助开发者实现很多有趣的功能，例如：

• 竞技类手游中的面对面组队功能
• 棋牌类手游中的面对面约局功能
• 近场AA收款功能
• 音乐曲目共享功能

欲了解更多详情

访问华为近距离通信服务官网
获取华为近距离通信服务开发指导文档
华为近距离通信服务开源仓库地址：GitHub、Gitee
华为HMS Core官方论坛 
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