Question

我正在开发一个应用程序，它将从网站获取并显示 JSON 数据，它在获取和显示数据时工作正常但是，我无法在数据时更新List-view在网站上被更改。

以下是异步任务的onPostExecute的 JAVA 代码：

@Override
protected void onPostExecute(Void result) {
    super.onPostExecute(result);
    // Dismiss the progress dialog
    if (pDialog.isShowing())
        pDialog.dismiss();
        /**
         * Updating parsed JSON data into ListView
         * */

        ListAdapter adapter = new SimpleAdapter(MainActivity.this, contactList, R.layout.list_item,
             new String[]{"field1","updated_at"}, new int[]{ R.id.field1,R.id.updated_at});

        listview.setAdapter(adapter);

    }
}

我尝试使用Handler，但它不起作用。

帮助将得到赞赏。

提前致谢！

更新

这是我的完整

private class GetContacts extends AsyncTask<Void, Void, Void> {

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        // Showing progress dialog
        pDialog = new ProgressDialog(MainActivity.this);
        pDialog.setMessage("Please wait...");
        pDialog.setCancelable(false);
        pDialog.show();

    }

    @Override
    protected Void doInBackground(Void... arg0) {


        HttpHandler sh = new HttpHandler();

        // Making a request to url and getting response
        String jsonStr = sh.makeServiceCall(url);

        Log.e(TAG, "Response from url: " + jsonStr);

        if (jsonStr != null) {
            try {
                JSONObject jsonObj = new JSONObject(jsonStr);


                // Getting JSON Array node
                JSONArray feeds = jsonObj.getJSONArray("feeds");

                // looping through All feeds
                for (int i = 0; i < feeds.length(); i++) {

                    JSONObject c = feeds.getJSONObject(i);

                    JSONObject chaObj=(new JSONObject(jsonStr)).getJSONObject("channel");

                    field1 = c.getString("field1");
                    updated_at = chaObj.getString("updated_at");
                    HashMap<String, String> contact = new HashMap<>();

                    contact.put("field1", field1);
                    contact.put("updated_at",updated_at);
                    contactList.add(contact);
                }
            } catch (final JSONException e) {
                Log.e(TAG, "Json parsing error: " + e.getMessage());
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        Toast.makeText(getApplicationContext(),
                                "Json parsing error: " + e.getMessage(),
                                Toast.LENGTH_LONG)
                                .show();
                    }
                });

            }
        } else {
            Log.e(TAG, "Couldn't get json from server.");
            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    Toast.makeText(getApplicationContext(),
                            "Couldn't get json from server. Check LogCat for possible errors!",
                            Toast.LENGTH_LONG)
                            .show();
                }
            });

        }


        return null;
    }

        @Override
        protected void onPostExecute(Void result) {
            super.onPostExecute(result);
            // Dismiss the progress dialog
            if (pDialog.isShowing())
                pDialog.dismiss();
            /**
             * Updating parsed JSON data into ListView
             * */

             ListAdapter adapter = new SimpleAdapter(MainActivity.this, contactList, R.layout.list_item,
                    new String[]{"field1","updated_at"}, new int[]{ R.id.field1,R.id.updated_at});

                lv.setAdapter(adapter);
        }


    }

Answer 1

不要尝试在onPostExecute中每次都设置适配器，只需设置一次list.notifyDataSetChanged（）就像这样：

if(adapter == null)
{
   ...set list and adapter work
}
else
{
   adapter.notifyDataSetChanged();
}

如何自动刷新或自动重新加载ListAdapter？

1 个答案: