google-cloud-messaging - 创建 GCM 客户端应用程序，asynctask 失败

Question

创建 GCM 客户端应用程序时，asynctask 出现编译错误。OnCreate 我们正在调用 registerBackgrouod，它将检查 gcm 实例是否正在运行，如果没有则创建一个。

但是 asyntask 给出错误:“Asynctask 无法解析为类型”

private void registerBackground() {
    new AsyncTask() {
        protected String doInBackground(Void... params) {
            String msg = "";
            try {
                if (gcm == null) {
                    gcm = GoogleCloudMessaging.getInstance(context);
                }
                regid = gcm.register(SENDER_ID);
                msg = "Device registered, registration id=" + regid;
                // You should send the registration ID to your server over HTTP,
                // so it can use GCM/HTTP or CCS to send messages to your app.
                // For this demo: we don't need to send it because the device
                // will send upstream messages to a server that echo back the message
                // using the 'from' address in the message.

                // Save the regid - no need to register again.
                setRegistrationId(context, regid);
            } catch (IOException ex) {
                msg = "Error :" + ex.getMessage();
            }
            return msg;
        }


        protected void onPostExecute(String msg) {
            mDisplay.append(msg + "\n");
        }
    }.execute(null, null, null);

Answer 1

正如 AlexBcn 已经观察到的，并根据 AsyncTask 的文档，您可以将三种类型作为参数传递给 AsyncTask。因为您想将 GCM 推送通知的有效负载作为字符串返回，所以您将调用 AsyncTask<Void, Void, String>

所以正确的GCM客户端代码片段是:

    private void registerInBackground() {
      new AsyncTask<Void, Void, String>() {
        @Override
        protected String doInBackground(Void... params) {
            String msg = "";
            try {
                if (gcm == null) {
                    gcm = GoogleCloudMessaging.getInstance(context);
                }
                regid = gcm.register(SENDER_ID);
                msg = "Device registered, registration ID=" + regid;

                // You should send the registration ID to your server over HTTP, so it
                // can use GCM/HTTP or CCS to send messages to your app.
                // For this demo: we don't need to send it because the device will send
                // upstream messages to a server that echo back the message using the
                // 'from' address in the message.

                // Persist the regID - no need to register again.
                storeRegistrationId(context, regid);
            } catch (IOException ex) {
                msg = "Error :" + ex.getMessage();
                // If there is an error, don't just keep trying to register.
                // Require the user to click a button again, or perform
                // exponential back-off.
            }
            return msg;
        }.execute(null, null, null);
    }