Android：如何将异步任务的结果传递给主线程？

Question

我有一个实现 AsyncTask 的类。

它计算一个对象（用户），我想将该对象返回给主（UI）线程以传递给一个新的活动。

我知道它是用 Activity.runOnUiThread() 完成的，但我不明白要传递给这个函数等什么？ （我想在主线程中设置一个变量 User usr = value ）

我该怎么办？

谢谢

编辑： 使用“Vipul Shah”代码我得到“无异常关闭”。 这是日志（来自 logcat）：

06-12 10:28:05.404: E/AndroidRuntime(1475): FATAL EXCEPTION: AsyncTask #1
06-12 10:28:05.404: E/AndroidRuntime(1475): java.lang.RuntimeException: An error occured while executing doInBackground()
06-12 10:28:05.404: E/AndroidRuntime(1475):     at android.os.AsyncTask$3.done(AsyncTask.java:278)
06-12 10:28:05.404: E/AndroidRuntime(1475):     at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
06-12 10:28:05.404: E/AndroidRuntime(1475):     at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
06-12 10:28:05.404: E/AndroidRuntime(1475):     at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
06-12 10:28:05.404: E/AndroidRuntime(1475):     at java.util.concurrent.FutureTask.run(FutureTask.java:137)
06-12 10:28:05.404: E/AndroidRuntime(1475):     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
06-12 10:28:05.404: E/AndroidRuntime(1475):     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
06-12 10:28:05.404: E/AndroidRuntime(1475):     at java.lang.Thread.run(Thread.java:856)
06-12 10:28:05.404: E/AndroidRuntime(1475): Caused by: java.lang.NullPointerException
06-12 10:28:05.404: E/AndroidRuntime(1475):     at org.ksoap2.serialization.SoapSerializationEnvelope.getResponse(SoapSerializationEnvelope.java:513)
06-12 10:28:05.404: E/AndroidRuntime(1475):     at es.es.ValidacionThread.doInBackground(ValidacionThread.java:65)
06-12 10:28:05.404: E/AndroidRuntime(1475):     at es.es.ValidacionThread.doInBackground(ValidacionThread.java:1)
06-12 10:28:05.404: E/AndroidRuntime(1475):     at android.os.AsyncTask$2.call(AsyncTask.java:264)
06-12 10:28:05.404: E/AndroidRuntime(1475):     at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
06-12 10:28:05.404: E/AndroidRuntime(1475):     ... 4 more

ValidacionTask 完整源代码：

package es.es;

import java.io.IOException;

import org.ksoap2.SoapEnvelope;
import org.ksoap2.SoapFault;
import org.ksoap2.serialization.SoapObject;
import org.ksoap2.serialization.SoapSerializationEnvelope;
import org.ksoap2.transport.HttpTransportSE;
import org.xmlpull.v1.XmlPullParserException;

import android.content.Context;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Handler;



public class ValidacionThread extends AsyncTask<String, Object, Usuario> {

    private final String NAMESPACE = "http://webservices.pcp/";
    private final String URL = "http://127.0.0.1:8080/webServices/pcpWS?wsdl";
    private final String SOAPACTION = "";
    private final String METHOD = "ValidarUsuario";
    private AccesoCuentaActivity act;

    //Handler handler;

    private Context context;

    public ValidacionThread(Context context){
        this.context = context;
    }

    protected Usuario doInBackground(String[] pars) {

                 String user = pars[0];
                 String password = pars[1];
                SoapObject request = new SoapObject(NAMESPACE, METHOD); 
                SoapSerializationEnvelope sobre = new SoapSerializationEnvelope(SoapEnvelope.VER11);
                sobre.dotNet = false;       
                request.addProperty("login", user);        
                request.addProperty("password", password); 
                sobre.setOutputSoapObject(request); 

                HttpTransportSE transporte = new HttpTransportSE(URL);        
                try {
                    transporte.call(SOAPACTION, sobre);
                } catch (IOException e) {
                //  JOptionPane.e.printStackTrace();
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                } catch (XmlPullParserException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                SoapObject resultado = null;
                try {
                    resultado = (SoapObject)sobre.getResponse();
                } catch (SoapFault e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }

                Usuario usu = new Usuario();
                usu.IdUsuario= resultado.getProperty(0).toString();
                usu.Nombre = resultado.getProperty(1).toString();
                usu.Apellidos = resultado.getProperty(2).toString();
                usu.Rol = resultado.getProperty(3).toString();   
                usu.Centro=resultado.getProperty(4).toString();
                return usu;     

}
       protected void onPostExecute(Usuario usu) {
          Intent intent = new Intent(context, MainActivity.class);
           intent.putExtra("result", usu);
           context.startActivity(intent);
           super.onPostExecute(usu);

        }

       protected void onProgress(Usuario usu) {

        }

}

Answer 1

它计算一个对象（用户），我想将该对象返回给 main (UI) 要传递给新活动的威胁。

对象的计算应该在doInBackground方法中进行，一旦完成就使用onPostExceute方法来做UI部分。

下面的 sn-p 会帮助你。

示例活动类。

    public class HelloActivity extends ListActivity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        new MyTask(this).execute("");
    }


}

MyTask.java

class MyTask extends AsyncTask<String, Object, String> {

        private Context context;

        public MyTask(Context context) {
            this.context = context;
        }

        @Override
        protected String doInBackground(String... params) {
            // Do background operations here and once done return the result.

            return result;
        }

        @Override
        protected void onPostExecute(String result) {

            // Here you will receive that result.

            Intent intent = new Intent(context, SecondActivity.class);
            intent.putExtra("result", result);
            context.startActivity(intent);
            super.onPostExecute(result);
        }

    }

Answer 2

我希望您知道我们提供给我们执行 UI 线程工作的 onPostExecute 和 onProgressUpdate..

如果仍然想要您在 AsyncTask 中的活动，那么可以在构造函数中传递它p>

public class MyAsyncTaskextends AsyncTask<String, Void, String> {
private <YOUR>Activity mActivity;

 public MyAsyncTaskextends (<YOUR>Activity activity){
          super();
         mActivity = activity;
}

Answer 3

最好的办法是使用 Handle 对象。

final Handler handler = new Handler() {
        public void handleMessage(Message msg) {
      User user = (User) msg.obj;
    // here is your code 
      }
};

在你的帖子里

msg = handler.obtainMessage();
msg.obj = user;
handler.sendMessage(msg);

不要忘记在 Tasks 构造函数中提供指向您的处理程序的链接