如何用HMS Nearby Service给自己的APP开发一个名片交换功能？

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（ ），快速实现一对一或一对多名片交换。下图是功能演示：

如果你对实现方式感兴趣，可以去去下载源代码，大家可以基于具体的应用场景优化。

demo下载地址：

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

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

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

@Overridepublic void onStart() {super.onStart();getActivity().getApplication().registerActivityLifecycleCallbacks(this);checkPermission();}@Overridepublic 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（），把名片添加到查找名片对话框中显示；名片消息丢失时（），从查找名片对话框中删除该名片

private MessageHandler mMessageHandler = new MessageHandler() {@Overridepublic 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);}@Overridepublic 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;}