如何从异步任务返回结果

Question

我一直在使用异步任务来访问Web服务器并使用结果更新控件.这有缺点,即它使异步方法特定于控制并使我再次使用返回的字符串.

如何从异步调用onPostExecute返回结果字符串？我怎么称呼它？我似乎无法让我的代码能够做到这一点.线程应该没有问题,因为我有一个冻结UI的对话框,直到完成工作.

我的典型asyncTask代码如下

class GetDataFromServer extends AsyncTask<String, String, String>
{
     * */
    // Progress Dialog
    private ProgressDialog qDialog;
    private Context context;
    private String dialogString;
    private ArrayList<String[]> newLoginResult;

    // JSON parser class
    String url_newGame ="http://xxxxxx.php";

    public myAsyncMethos(String dialogMessage, Context con)
    {
        this.qDialog =  new ProgressDialog(con);
        this.dialogString = dialogMessage;
        this.context = con;
    }

    /**
     * Before starting background thread Show Progress Dialog
     * */
    @Override
    protected void onPreExecute()
    {
        super.onPreExecute();
        qDialog = new ProgressDialog(this.context);
        qDialog.setMessage(this.dialogString);
        qDialog.setIndeterminate(false);
        qDialog.setCancelable(false);
        qDialog.show();
    }

    @Override
    protected JSONObject doInBackground(String... args)
    {
        //MAKE SERVER CALL and cast to JSONOBject

        return jsonNewUser;
    }

    public void onPostExecute(JSONObject jsonString)
    {

         // dismiss the dialog after getting response
        qDialog.dismiss();
//I WANT TO RETURN A STRING HERE BUT KEEP GETTING SYNTAX ERRORS BEFORE RUNTIME


    }
}

Answer 1

我个人会向您的类添加一个回调，然后一旦onPostExecute运行，就向主类上的侦听器触发回调。

class GetDataFromServer extends AsyncTask<String, String,JSONObject>
{
    // Progress Dialog
    private ProgressDialog qDialog;
    private Context context;
    private String dialogString;
    private ArrayList<String[]> newLoginResult;
    private InformComplete myCallback;

    public GetDataFromServer(String dialogMessage, Context con,InformComplete callback)
    {
        this.qDialog =  new ProgressDialog(con);
        this.dialogString = dialogMessage;
        this.context = con;
        this.myCallback=callback;
    }

    @Override
    protected void onPreExecute()
    {
        // set up your dialog
    }

    @Override
    protected JSONObject doInBackground(String... args)
    {
        JSONObject jsonNewUser=new JSONObject();
        return jsonNewUser;
    }

    public void onPostExecute(JSONObject jsonString)
    {
        qDialog.dismiss();
        myCallback.PostData(jsonString);
    }
    public interface InformComplete
    {
        public void PostData(JSONObject result);
    }
}

然后从你的调用类中，你会得到这样的东西......

    private void callTheAsyncThing
    {
        GetDataFromServer gds=new GetDataFromServer("please wait", this, letMeKnow);
        gds.execute(params);
    }

    private InformComplete letMeKnow=new InformComplete()
    {
        public void PostData(JSONObject result)
        {
            // we now have the data in the calling class
        }
    };