在服务中运行 AsyncTask - Android答案

【问题标题】：Run AsyncTask in Service - Android在服务中运行 AsyncTask - Android
【发布时间】：2017-07-01 20:24:31
【问题描述】：

我正在尝试在 android Service 中使用 AsyncTask，但它不起作用。有人可以帮助我吗？我正在使用片段，我是新手。提前致谢。错误：无法解析方法。这是我的实现。

public class MyService extends Service implements Runnable {

final String numeroPorta = "80";
final String nomeParametro = "num";
String respostaServidor;
private boolean ativo;

@Override
public IBinder onBind(Intent intent) {
    return null;
}

@Override
public void onCreate() {
    super.onCreate();
}

@Override
public int onStartCommand(Intent intent, int flags, int startID) {

    ativo = true;
    new Thread(this, "MyService" + startID).start();
    return super.onStartCommand(intent, flags, startID);
}

@Override
public void run() {
    myService();
}

@Override
public void onDestroy() {
    ativo = false;
}

public void myService() {
    new Thread() {
        public void run() {
            runOnUiThread(new Runnable() {
                public void run() {
                    if (enderecoIP.length() > 0 && numeroPorta.length() > 0 && !Objects.equals(valorParametro, "0")) {
                        new HttpRequestAsyncTask(getApplicationContext(), valorParametro, enderecoIP, numeroPorta, nomeParametro).execute();
                    }
                }
            });
        }
    }.start();
}

public class HttpRequestAsyncTask extends AsyncTask<Void, Void, Void> {

    private String requisicaoResposta, enderecoIP, numeroPorta;
    private Context contexto;
    private AlertDialog alerta;
    private String parametro, valorParametro;

    HttpRequestAsyncTask(Context contexto, String valorParametro, String enderecoIP, String numeroPorta, String parametro) {

        this.contexto = contexto;

        alerta = new AlertDialog.Builder(this.contexto)
                .setTitle("Resposta HTTP:")
                .setCancelable(true)
                .create();

        this.enderecoIP = enderecoIP;
        this.numeroPorta = numeroPorta;
        this.valorParametro = valorParametro;
        this.parametro = parametro;
    }


    @Override
    protected Void doInBackground(Void... voids) {

        alerta.setMessage("Dados enviados, aguardando resposta do servidor...");
        if (!alerta.isShowing()) {
            alerta.show();
        }

        requisicaoResposta = sendRequest(valorParametro, enderecoIP, numeroPorta, parametro);
        return null;
    }

    @Override
    protected void onPostExecute(Void avoid) {

        alerta.setMessage(requisicaoResposta);
        if (!alerta.isShowing()) {
            alerta.show();
        }
    }

    @Override
    protected void onPreExecute() {

        alerta.setMessage("Enviando dados ao servidor, por favor aguarde...");
        if (!alerta.isShowing()) {
            alerta.show();
        }
    }
}

}

【问题讨论】：

您正在尝试在服务中调用runOnUiThread；此方法仅在 Activity 中可用。就此而言，在服务中您甚至不需要使用 AsyncTask，只需使用您创建的线程来发出请求。

标签： android service android-asynctask

【解决方案1】：

看看这段代码是否可行..

public class MyService extends Service {

    @Override
    public IBinder onBind(Intent arg0) {
        return null;
    }

    @Override 
    public int onStartCommand(Intent intent,int flags,int startId) {

        //We want this service to continue running until it is explicitly    
        //stopped,so return sticky. 

        Toast.makeText(this, "ServiceStarted",Toast.LENGTH_LONG).show();

        try {
            new DoBackgroundTask().execute(new URL(""), new URL("")); 
        } catch (MalformedURLException e) {
            e.printStackTrace();
        }

        return START_STICKY;
    }

    @Override
    public void onDestroy() {    
        super.onDestroy();

        Toast.makeText(this,"ServiceDestroyed",Toast.LENGTH_LONG).show(); 
    } 

    private int DownloadFile(URL url) {
        try {    
            //---simulate taking sometime to download a file--- 

            Thread.sleep(5000);
        } catch(InterruptedException e) {
            e.printStackTrace(); 
        }

        //---return an arbitrary number representing 
        //the size of the file downloaded---     

        return 100;    
    }

    private class DoBackgroundTask extends AsyncTask<URL, Integer, Long> {

        protected Long doInBackground(URL... urls) {    
            int count = urls.length;
            long totalBytesDownloaded = 0;

            for (int i = 0; i < count; i++) {
                totalBytesDownloaded += DownloadFile(urls[i]);

                //---calculate percentage downloaded and
                // report its progress--- 

                publishProgress((int) (((i+1) / (float) count) * 100));
            }

            return totalBytesDownloaded;     
        }

        protected void onProgressUpdate(Integer... progress) {
            Log.d("Downloading files", String.valueOf(progress[0]) + "% downloaded");

            Toast.makeText(getBaseContext(), String.valueOf(progress[0]) + "% downloaded", Toast.LENGTH_LONG).show();
        }

        protected void onPostExecute(Long result) {
            Toast.makeText(getBaseContext(), "Downloaded " + result + " bytes", Toast.LENGTH_LONG).show();

            stopSelf();
        } 
    }
}

【讨论】：

我想发出一个 http 请求。