Android - 接收广播意图时出错？

Question

我有一个service 将String of Json 传递给MainActivity：

GetSubjects.class ：

public class GetSubjects extends Service {
    String URL = "http://webservice.jim.com/YYY/XXXX.asmx";
    String Webresponse = "IS NULL ?";
    int scode = 1597536485;
    String result;
    public final static String MY_ACTION = "MY_ACTION";
    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    @Override
    public int onStartCommand(final Intent intent, int flags, final int startId) {
        Runnable r = new Runnable() {
            @Override
            public void run() {
                handleStart(intent, startId);
            }
        };
        Thread t = new Thread(r);
        t.start();
        return START_NOT_STICKY;
    }

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

    void handleStart(Intent intent, int startId) {
        try {
            Params_GetSubjects param = new Params_GetSubjects(scode);
            result = new mGetSubjects().execute(param).get();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (ExecutionException e) {
            e.printStackTrace();
        }
    }

    public class mGetSubjects extends AsyncTask<Params_GetSubjects, String, String> {

        String NAMESPACE = "http://tempuri.org/";
        String METHOD_NAME = "Get";
        String SOAP_ACTION = "http://tempuri.org/Get";
        @Override
        protected String doInBackground(Params_GetSubjects... params) {
            SoapObject request = new SoapObject(NAMESPACE, METHOD_NAME);
            request.addProperty("scode", params[0].Scode);
            SoapSerializationEnvelope envelope = new SoapSerializationEnvelope(SoapEnvelope.VER11);
            envelope.dotNet = true;
            envelope.setOutputSoapObject(request);
            HttpTransportSE conn = new HttpTransportSE(URL);
            Object object;
            try {
                conn.call(SOAP_ACTION, envelope);
                //SoapPrimitive response = (SoapPrimitive) envelope.getResponse();
                object = envelope.getResponse();
                Webresponse = object.toString();
            } catch (Exception e) {
                e.printStackTrace();
                return "NULL";
            }finally {
                ThreadFinish threadfinish = new ThreadFinish();
                threadfinish.start();
                return Webresponse;
            }
        }
    }
    public class ThreadFinish extends Thread{

        @Override
        public void run() {
            try {
                Intent intent = new Intent();
                intent.setAction(MY_ACTION);
                intent.putExtra("DATAPASSED", result);
                sendBroadcast(intent);
            }catch (Exception e){
                e.printStackTrace();
            }finally {
                stopSelf();
            }
        }
    }
}

这是我的 MainActivity：

public class MainActivity extends AppCompatActivity {
    MyReceiver myReceiver;
    private RecyclerView.LayoutManager layoutManager;
    private DrawerAdapter mDrawerAdapter;
    private RecyclerView mRecyclerView;
    List<DrawerItem> draweritemList;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        startService(new Intent(MainActivity.this, GetSubjects.class));

    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        switch (id) {
            case android.R.id.home:
                mDrawerLayout.openDrawer(GravityCompat.START);
                return true;
            case R.id.action_settings:
                return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @Override
    protected void onStart() {
        myReceiver = new MyReceiver();
        IntentFilter intentFilter = new IntentFilter();
        intentFilter.addAction(GetSubjects.MY_ACTION);
        registerReceiver(myReceiver, intentFilter);
        super.onStart();
    }

    @Override
    protected void onStop() {
        this.unregisterReceiver(myReceiver);
        super.onStop();
    }

    private class MyReceiver extends BroadcastReceiver {

        @Override
        public void onReceive(Context arg0, Intent arg1) {

                String datapassed = arg1.getExtras().getString("DATAPASSED");
                Log.i("ASDQWRRYGH",datapassed);

                draweritemList  = JsonParser.parseFeed(datapassed);

                for (int i=0;i < draweritemList.size();i++)
                {
                    Log.i("ASDQWRRYGH",draweritemList.get(i).getTitle());
                }



        }

    }
}

这是我的 JsonParer：

public class JsonParser {
    public static List<DrawerItem> parseFeed(String content) {
        try {
            JSONObject jsonRootObject = new JSONObject(content);
            JSONArray jsonArray = jsonRootObject.optJSONArray("Rows");
            List<DrawerItem> draweritemList = new ArrayList<>();
            for (int i = 0; i < jsonArray.length(); i++) {
                JSONObject obj = jsonArray.getJSONObject(i);
                DrawerItem draweritem = new DrawerItem();

                draweritem.setId(obj.getString("Id"));
                draweritem.setTitle(obj.getString("Title"));
                draweritemList.add(draweritem);
            }
            return draweritemList;
        } catch (JSONException e) {
            e.printStackTrace();
            return null;
        }
    }
}

经常给我服务结果，但经常给我下面的错误，我该怎么办？：

Answer 1

您的Service 中执行了三个额外的线程； AsyncTask 和两个 Threads。第一个Thread 正在执行你的AsyncTask，但它是阻塞的，因为你在它上面调用get() 以将返回值分配给returnString。当网络事务在AsyncTask 中完成时，它开始另一个Thread 发送广播，这发生在doInBackground() 可以返回设置return 的值之前String，最终得到广播，而它仍然是空的。

最简单的解决方法是将广播移动到result = ... 行之后，并去掉ThreadFinish 类。

不过，最好在单个线程中按顺序执行所有内容；在AsyncTask 或Thread 中执行您的Runnable。