Question

我想解析来自此网址http://inspirontrance.com/tpb.json的JSON数据。我的代码在没有AsyncTask但没有启用AsyncTask的情况下工作，应用程序在加载一定次数后崩溃。虽然我的代码似乎没问题，但不知何故，应用程序在异步过程中冻结。

这是我的代码，

    public class AndroidJSONParsingActivity extends ListActivity {

    // url to make request
    private static String url = "http://inspirontrance.com/tpb.json";

    // JSON Node names
    private static final String TAG_UPLOADS = "uploads";
    private static final String TAG_ID = "id";
    private static final String TAG_NAME = "name";
    private static final String TAG_DATE = "date";

    ProgressDialog pDialog;

    // JSONArray
    JSONArray uploads = null;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        new MyAsyncTask().execute(url);
        // Showing progress dialog before sending http request
        pDialog = new ProgressDialog(this);
        pDialog.setMessage("Please wait..");
        pDialog.setIndeterminate(true);
        pDialog.setCancelable(false);
        pDialog.show();
    }

    class MyAsyncTask extends
            AsyncTask<String, Integer, ArrayList<HashMap<String, String>>> {

        // Hashmap for ListView
        ArrayList<HashMap<String, String>> UploadsList = new ArrayList<HashMap<String, String>>();

        @Override
        protected ArrayList<HashMap<String, String>> doInBackground(
                String... params) {

            // Creating JSON Parser instance
            JSONParser jParser = new JSONParser();

            // getting JSON string from URL
            JSONObject json = jParser.getJSONFromUrl(url);

            try {
                // Getting Array of Uploads
                uploads = json.getJSONArray(TAG_UPLOADS);

                // looping through All Uploads
                for (int i = 0; i < uploads.length(); i++) {
                    JSONObject c = uploads.getJSONObject(i);

                    // Storing each json item in variable
                    String id = c.getString(TAG_ID);
                    String name = c.getString(TAG_NAME);
                    String date = c.getString(TAG_DATE);

                    // creating new HashMap
                    HashMap<String, String> map = new HashMap<String, String>();

                    // adding each child node to HashMap key => value
                    map.put(TAG_ID, id);
                    map.put(TAG_NAME, name);
                    map.put(TAG_DATE, date);

                    // adding HashList to ArrayList
                    UploadsList.add(map);
                }
            } catch (JSONException e) {
                e.printStackTrace();
            }

            return UploadsList;
        }

    }

    protected void onPostExecute(ArrayList<HashMap<String, String>> result) {

        pDialog.dismiss();

        ListAdapter adapter = new SimpleAdapter(this, result,
                R.layout.list_item,
                new String[] { TAG_NAME, TAG_ID, TAG_DATE }, new int[] {
                        R.id.name, R.id.id, R.id.date });

        setListAdapter(adapter);
    }
}

Answer 1

我是这样做的。养成在任务中完成前/后工作的习惯是很好的。

class MyAsyncTask extends
        AsyncTask<String, Integer, ArrayList<HashMap<String, String>>> {

    // Hashmap for ListView
    ArrayList<HashMap<String, String>> UploadsList = new ArrayList<HashMap<String, String>>();

    @Override
    protected void onPreExecute() {
        // Showing progress dialog before sending http request
        pDialog = new ProgressDialog(this);
        pDialog.setMessage("Please wait..");
        pDialog.setIndeterminate(true);
        pDialog.setCancelable(false);
        pDialog.show();        }

    @Override
    protected ArrayList<HashMap<String, String>> doInBackground(
            String... params) {

        // Creating JSON Parser instance
        JSONParser jParser = new JSONParser();

        // getting JSON string from URL
        JSONObject json = jParser.getJSONFromUrl(url);

        try {
            // Getting Array of Uploads
            uploads = json.getJSONArray(TAG_UPLOADS);

            // looping through All Uploads
            for (int i = 0; i < uploads.length(); i++) {
                JSONObject c = uploads.getJSONObject(i);

                // Storing each json item in variable
                String id = c.getString(TAG_ID);
                String name = c.getString(TAG_NAME);
                String date = c.getString(TAG_DATE);

                // creating new HashMap
                HashMap<String, String> map = new HashMap<String, String>();

                // adding each child node to HashMap key => value
                map.put(TAG_ID, id);
                map.put(TAG_NAME, name);
                map.put(TAG_DATE, date);

                // adding HashList to ArrayList
                UploadsList.add(map);
            }
        } catch (JSONException e) {
            e.printStackTrace();
        }

        return UploadsList;
    }

    @Override
    protected void onPostExecute(ArrayList<HashMap<String, String>> result) {

        pDialog.dismiss();

        ListAdapter adapter = new SimpleAdapter(this, result,
                R.layout.list_item,
                new String[] { TAG_NAME, TAG_ID, TAG_DATE }, new int[] {
                R.id.name, R.id.id, R.id.date });

        setListAdapter(adapter);
    }
}

使用Android中的AsyncTask在JSON数据中加载ListView

1 个答案: