android - 与可穿戴设备交互的服务

Question

我尝试创建一个服务（扩展WearableListenerService），该服务应该发送以及使用wearable接收数据。 但是当我在该服务中创建GoogleApiClient对象时，它失败并出现NullPointerException 。

public class MyService extends WearableListenerService{

    private GoogleApiClient mGoogleApiClient = new GoogleApiClient.Builder(this)
        .addApi(Wearable.API)
        .build();
    private final String MESSAGE_PATH = "/message";
    private String remoteNodeId;


    @Override
    public void onMessageReceived(MessageEvent messageEvent) {
         Log.d("myMessage",messageEvent.getData());
         remoteNodeId = messageEvent.getSourceNodeId();
         sendMessage("Content received");
    }

    public void sendMessage(String message) {

         Wearable.MessageApi.sendMessage(mGoogleApiClient,
                 remoteNodeId,MESSAGE_PATH,message.getBytes());
    }

}

每当我尝试运行此程序时，我都会收到NullPointerException声明部分mGoogleApiClient的错误消息。

Answer 1

覆盖Service中的onCreate，并在其中初始化mGoogleApiClient

private GoogleApiClient mGoogleApiClient;

public void onCreate() {
  super.onCreate();
  mGoogleApiClient = new GoogleApiClient.Builder(this)
        .addApi(Wearable.API)
        .build();
}

Answer 2

不要忘记致电mGoogleApiClient.connect();