Update UI Asynchronously in Android

问题

I have a webservice call which is called every 10 seconds and should update a TextView with the webservice reply(or atleast show a toast message every 10 seconds)

But the UI is not getting updated at all.

Please find the code below.

public class MessagesRequestActivity extends Activity  {
    /** Called when the activity is first created. */
    String currentMsg="Default";
    @Override
    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        //Calling the webservice
        getMessage();
    }
    public void getMessage(){

        try
        {
        SoapObject request = new SoapObject("http://tempuri.org/", "getMessage");

        SoapSerializationEnvelope envelope = new SoapSerializationEnvelope(SoapEnvelope.VER11);
        envelope.dotNet = true;
        envelope.setOutputSoapObject(request);

        //Web method call
        HttpTransportSE androidHttpTransport = new HttpTransportSE("http://192.168.4.50/WebService.asmx");
        androidHttpTransport.call("http://tempuri.org/"+ "getMessage", envelope);
        //get the response
        SoapPrimitive response = (SoapPrimitive)envelope.getResponse();

        //the response object can be retrieved by its name: result.getProperty("objectName");
        String message = (String)response.toString();
        Toast.makeText(this, message, Toast.LENGTH_LONG).show();

        }
        catch (Exception e)
        {
        e.printStackTrace();
        }
        try {
            Thread.sleep(10000);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        }
}

回答1:

Here is an example of an AsyncTask

public class TalkToServer extends AsyncTask<String, String, String> {
@Override
protected void onPreExecute() {
    super.onPreExecute();
}

@Override
protected void onProgressUpdate(String... values) {
    super.onProgressUpdate(values);

}

@Override
protected String doInBackground(String... params) {
//do your work here
    return something;
}

@Override
protected void onPostExecute(String result) {
    super.onPostExecute(result);
       // do something with data here-display it or send to mainactivity
}

Then you can access by calling

TalksToServer varName = new TalkToServer(); //pass parameters if you need to the constructor
varName.execute();

Async Docs Progress Dialog Example

You don't want to do network stuff or call sleep on the UI thread. If it is an inner class then you will have access to your member variables of the outer class. Otherwise, create a contructor in the AsyncTask class to pass context if you want to update from onPostExecute or other methods besids doInBackground().

回答2:

As everyone has mentioned, you're making network calls in the UI thread and performing Thread.Sleep() which freezes your UI.

I'd try something like this AsyncHttpClient class, it has all the functionality you need, you'll have to perform your UI updates in the callback.

http://loopj.com/android-async-http/

来源：https://stackoverflow.com/questions/15297996/update-ui-asynchronously-in-android