Question

我正在尝试设计一个使用AsyncTask实现方法的帮助器类。

public interface ResultCallback
{
    public String processResult();
}

public class ServerAdapter
{

    // Required processResult to call this method. Kind of lousy but I do not know
    // how to throw exception from onPostExcecute in AsyncTask.
    public String getResult() throws AirplaneModeException, NoNetworkException
    {
       // code to get return value from Dowork throw exceptions on errors
    }

    public void getLicense(ResultCallback licenseCallback)
    {
        ...// Set url, outmessage
        new Dowork(url, outMessage, licenseCallback).execute();
    }

    public void queryServer(int queryId, ArrayList<String> args, ResultCallback queryCallback)
    {
        ...// Set url, outmessage
        new Dowork(url, outmessage, queryCallback);
    }

    private class Dowork extends AsyncTask<Void, Void, String>
    {
        ...
        private ResultCallback rc;

        public Dowork(String url, String outMessage, ResultCallback rc)
        {
            // code here
        }

        protected String doInBackground(Void... params)
        {
            try
            {
                 // code here
            }
            catch (AirplaneModeException e)
            {
                return "AirplaneModeException";
            }
            catch ...
         }

         protected void onPostExecute(String result)
         {
             this.result = result;
             cb.processResult();
         }
    }
}

// Client class
public class myclass extends Activity
{
    MyServerAdapter myAdapter;

    public void onCreate(Bundle savedInstanceState)
    {
        ...
        myAdapter = new ServerAdapter();
        myAdapter.getLicence(new MyLicenseCallback);
        myAdapter.queryServer(id, args, new MyQueryCallback);
        ...
    }

    public class MyLicenseCallback extends ResultCallback implements processResult
    {
        try
        {
            String result = myAdapter.getResult;
            ...
        }
        catch
        ... 
    }
    ...

}

我是Java和Android的新手，有几个问题：

1-几个ServerAdapter方法调用会导致同步问题吗？例如，当MyLicense回调的代码正在运行时，如果onPostExecute调用MyQueryCallback，我是否必须处理它或Java处理它？</ p>

2-如何在回调中抛出异常，而不是像上面的代码那样解决？

Answer 1

Android保证您的活动中的方法和AsyncTask.onPostExecute在相同的主UI线程中运行。
您可以使用与结果相同的方式将异常保存在任务实例变量中（在这种情况下返回，比如说null）。检查是否存在异常以便处理错误情况。

Answer 2

仅适用于土耳其人:( http://aaarkonusurum.blogspot.com/2011/10/asynctask-classtan-donen-parametreyi.html

如何使用AsyncTask从helper类返回值

2 个答案: