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：
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 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 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 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
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