只为最后一个json对象获取值的onPostExecute()

Question

我已经成功地实现了parsed JSON，并为两个对象获得了值，比如：AsyncTask中的图像、句点，但在onPostExecute()方法中，我只为last json object获取value。

在这里，我只得到期间的最后一个对象值：

 delay, period); // getting last object's period value only

为什么在onPostExecute()方法中只能得到句点对象的最后一个对象值？

MainActivity.java:

public class MainActivity extends Activity {

    ArrayList<String> actorsList;
    ViewFlipper viewFlipper;    
    Handler mHandler ;
    Timer timer;
    Runnable mUpdateResults;
    int delay = 500;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        viewFlipper = (ViewFlipper) findViewById(R.id.flipper);

        actorsList = new ArrayList<String>();

        // execute AsyncTask
        new JSONAsyncTask().execute("http://localhost/images.txt");

        // handler to set duration and to upate animation
        mHandler = new Handler();

        // Create runnable for posting
        mUpdateResults = new Runnable() {
            public void run() {
                viewFlipper.showNext(); // showNext() method
            }
        };

        timer = new Timer();        
    }

    // AsyncTask to get data from server
    class JSONAsyncTask extends AsyncTask<String, Void, Boolean> {
        int period;
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
        }

        @Override
        protected Boolean doInBackground(String... urls) {
            try {

                //------------------>>
                HttpGet httppost = new HttpGet(urls[0]);
                HttpClient httpclient = new DefaultHttpClient();
                HttpResponse response = httpclient.execute(httppost);

                // StatusLine stat = response.getStatusLine();
                int status = response.getStatusLine().getStatusCode();

                if (status == 200) {
                    HttpEntity entity = response.getEntity();
                    String data = EntityUtils.toString(entity);

                    JSONObject jsono = new JSONObject(data);
                    JSONArray jarray = jsono.getJSONArray("images");

                    for (int i = 0; i < jarray.length(); i++) {
                        JSONObject object = jarray.getJSONObject(i);

                        actorsList.add(object.getString("image"));
                        Log.d("image: ", object.getString("image"));                        
                        try {
                            period = Integer.parseInt(object.getString("period").toString());
                            Log.d("period: ", object.getString("period"));
                        } catch (NumberFormatException nfe) {
                            // TODO: handle exception
                            System.out.print("could not parse:" + nfe);
                        }                       
                    }
                    return true;
                }

            } catch (ParseException e1) {
                e1.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            } catch (JSONException e) {
                e.printStackTrace();
            }
            return false;
        }

    protected void onPostExecute(Boolean result) {
        if(result == false)
        {
            Toast.makeText(getApplicationContext(), "Unable to fetch data from server", Toast.LENGTH_LONG).show();
        }
        else
        {           
            for(int i=0; i<actorsList.size(); i++)
            {
                ImageView image = new ImageView(getApplicationContext());              

                Picasso.with(MainActivity.this)
                .load(actorsList.get(i).toString())
                .placeholder(R.drawable.ic_launcher)
                .error(R.drawable.ic_launcher)
                .into(image);

                viewFlipper.addView(image); // addView(..) method
            }           

             Log.d("period:post- ", String.valueOf(period));
             timer.scheduleAtFixedRate(new TimerTask() {

                public void run() {
                    mHandler.post(mUpdateResults);
                }
            }, delay, period); // getting last object's period value only

          }
       }
    }
}

Logcat:

10-10 11:46:52.527: D/image:(542): http://localhost/image_01.jpg
10-10 11:46:52.536: D/period:(542): 50000
10-10 11:46:52.536: D/image:(542): http://localhost/image_05.jpg
10-10 11:46:52.536: D/period:(542): 5000
10-10 11:46:52.536: D/image:(542): http://localhost/image_06.jpg
10-10 11:46:52.536: D/period:(542): 5000
10-10 11:46:52.546: D/image:(542): http://localhost/image_07.jpg
10-10 11:46:52.546: D/period:(542): 25000
10-10 11:46:52.546: D/image:(542): http://localhost/image_08.jpg
10-10 11:46:52.546: D/period:(542): 5000
10-10 11:46:52.546: D/image:(542): http://localhost/image_02.jpg
10-10 11:46:52.556: D/period:(542): 5000
10-10 11:46:52.556: D/image:(542): http://localhost/image_03.jpg
10-10 11:46:52.556: D/period:(542): 1000
10-10 11:46:52.556: D/image:(542): http://localhost/image_04.jpg
10-10 11:46:52.566: D/period:(542): 1000
10-10 11:46:52.616: D/period:post-(542): 1000

Answer 1

因为在这个循环中：

       for (int i = 0; i < jarray.length(); i++) {
                    JSONObject object = jarray.getJSONObject(i);

                    actorsList.add(object.getString("image"));
                    Log.d("image: ", object.getString("image"));                        
                    try {
                        period = Integer.parseInt(object.getString("period").toString());
                        Log.d("period: ", object.getString("period"));
                    } catch (NumberFormatException nfe) {
                        // TODO: handle exception
                        System.out.print("could not parse:" + nfe);
                    }                       
                }

当它结束时，您的period等于您解析的最后一个json。

public class MainActivity extends Activity {

    ArrayList<String> actorsList;
    ViewFlipper viewFlipper;    
    Handler mHandler ;
    Timer timer;
    List<Integer> periodsList;
    Runnable mUpdateResults;
    int delay = 500;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        periodsList=new ArrayList<Integer>();

        viewFlipper = (ViewFlipper) findViewById(R.id.flipper);

        actorsList = new ArrayList<String>();

        // execute AsyncTask
        new JSONAsyncTask().execute("http://localhost/images.txt");

        // handler to set duration and to upate animation
        mHandler = new Handler();

        // Create runnable for posting
        mUpdateResults = new Runnable() {
            public void run() {
                viewFlipper.showNext(); // showNext() method
            }
        };

        timer = new Timer();        
    }

    // AsyncTask to get data from server
    class JSONAsyncTask extends AsyncTask<String, Void, Boolean> {
        int period;
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
        }

        @Override
        protected Boolean doInBackground(String... urls) {
            try {

                //------------------>>
                HttpGet httppost = new HttpGet(urls[0]);
                HttpClient httpclient = new DefaultHttpClient();
                HttpResponse response = httpclient.execute(httppost);

                // StatusLine stat = response.getStatusLine();
                int status = response.getStatusLine().getStatusCode();

                if (status == 200) {
                    HttpEntity entity = response.getEntity();
                    String data = EntityUtils.toString(entity);

                    JSONObject jsono = new JSONObject(data);
                    JSONArray jarray = jsono.getJSONArray("images");

                    for (int i = 0; i < jarray.length(); i++) {
                        JSONObject object = jarray.getJSONObject(i);

                        actorsList.add(object.getString("image"));
                        Log.d("image: ", object.getString("image"));                        
                        try {

                            period = Integer.parseInt(object.getString("period").toString());
                            periodsList.add(Integer.parseInt(object.getString("period").toString()));
                            Log.d("period: ", object.getString("period"));
                        } catch (NumberFormatException nfe) {
                            // TODO: handle exception
                            System.out.print("could not parse:" + nfe);
                        }                       
                    }
                    return true;
                }

            } catch (ParseException e1) {
                e1.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            } catch (JSONException e) {
                e.printStackTrace();
            }
            return false;
        }

    protected void onPostExecute(Boolean result) {
        if(result == false)
        {
            Toast.makeText(getApplicationContext(), "Unable to fetch data from server", Toast.LENGTH_LONG).show();
        }
        else
        {           
            for(int i=0; i<actorsList.size(); i++)
            {
                ImageView image = new ImageView(getApplicationContext());              

                Picasso.with(MainActivity.this)
                .load(actorsList.get(i).toString())
                .placeholder(R.drawable.ic_launcher)
                .error(R.drawable.ic_launcher)
                .into(image);

                viewFlipper.addView(image); // addView(..) method
            }           


            int mDelay = 0;
            for(int i=0; i<periodsList.size(); i++)
            {
             Log.d("period:post- ", String.valueOf(periodsList.get(i)));
             timer.schedule(new TimerTask() {

                public void run() {
                    mHandler.post(mUpdateResults);
                }
            }, mDelay);

            mDelay = mDelay  + periodsList.get(i);

          }
         }
       }
    }
}

Answer 2

你得再做一个艺术家。

在这个列表中，您只需要添加句点(就像对actorsList那样)

主类添加

ArrayList<Integer> periods;

在onCreate()

periods=new ArrayList<Integer>();

在doInBackground中

try {
     periods.add(Integer.parseInt(object.getString("period").toString()));

    Log.d("period: ", object.getString("period"));
    } catch (NumberFormatException nfe) {
    System.out.print("could not parse:" + nfe);
}