Java Android ListView未显示，但json中的数据存在

问题是有时列表没有显示，我的网络连接正常。 我试过几次运行这个应用程序。1/10运行，列表在那里，我可以看到数据库中的数据。我真的不知道问题出在哪里 我用截击来获取数据

package com.example.wackyroad.internannouncement;


public class MainActivity extends ListActivity {

private static final String GET_URL = "http://XXX";
private static final String TAG_ID = "id";
private static final String TAG_TITLE = "title";
private static final String TAG_CONTENT = "content";
private static final String TAG_DATE = "date";
private ArrayList<HashMap<String, String>> listArrayList = new ArrayList<HashMap<String, String>>();
private ProgressDialog pDialog;
private ListAdapter adapter;

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

    getAnnouncement();
    updateList();

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
}

@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();

    //noinspection SimplifiableIfStatement
    if (id == R.id.refresh) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}


private void getAnnouncement() {
    StringRequest postRequest = new StringRequest(Request.Method.POST, GET_URL,
            new Response.Listener<String>() {
                @Override
                public void onResponse(String response) {

                    try {
                        JSONObject jsonResponse = new JSONObject(response);

                        try {
                            JSONArray data = jsonResponse.getJSONArray("announcements");

                            for (int i = 0; i < data.length(); i++) {
                                JSONObject c = data.getJSONObject(i);

                                HashMap<String, String> map = new HashMap<String, String>();
                                map.put(TAG_ID, c.getString("announcement_id"));
                                map.put(TAG_TITLE,  c.getString("announcement_title"));
                                map.put(TAG_CONTENT, c.getString("announcement_content"));
                                map.put(TAG_DATE, c.getString("announcement_date"));
                                listArrayList.add(map);
                            }

                        } catch (Exception e) {
                            e.printStackTrace();

                        }
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                    pDialog.dismiss();
                }
            },
            new Response.ErrorListener() {
                @Override
                public void onErrorResponse(VolleyError error) {
                    error.printStackTrace();
                    pDialog.dismiss();
                }
            }

    ) {
    };

    pDialog = new ProgressDialog(MainActivity.this);
    pDialog.setMessage("Getting Announcements..");
    pDialog.show();

    Volley.newRequestQueue(getApplication()).add(postRequest);

}

private void updateList() {
     adapter = new SimpleAdapter(this, listArrayList,
            R.layout.activity_lv_list, new String[]{TAG_ID, TAG_TITLE, TAG_CONTENT,
            TAG_DATE}, new int[]{R.id.tv_id, R.id.tv_title, R.id.tv_content, R.id.tv_date});


    setListAdapter(adapter);

    ListView lv = getListView();
    lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {

        @Override
        public void onItemClick(AdapterView<?> parent, View view,
                                int position, long id) {
            String tv_id = ((TextView) view.findViewById(R.id.tv_id)).getText().toString();
            Intent i = new Intent(getApplicationContext(), Announcement_Details.class);
            i.putExtra("id", tv_id);
            startActivity(i);

        }
    });
}


}

我认为问题在于listview中的数据填充是异步操作。 请求完成后，必须调用updateList（）方法

getAnnouncement（）是异步操作。 请求完成后，必须调用updateList（）方法

在更新hashmap之后调用updateList（），如

                          try {
                            JSONArray data = jsonResponse.getJSONArray("announcements");

                            for (int i = 0; i < data.length(); i++) {
                                JSONObject c = data.getJSONObject(i);

                                HashMap<String, String> map = new HashMap<String, String>();
                                map.put(TAG_ID, c.getString("announcement_id"));
                                map.put(TAG_TITLE,  c.getString("announcement_title"));
                                map.put(TAG_CONTENT, c.getString("announcement_content"));
                                map.put(TAG_DATE, c.getString("announcement_date"));
                                listArrayList.add(map);
                            }
                            updateList();
                        } catch (Exception e) {
                            e.printStackTrace();

                        }

试试看{
JSONArray data=jsonResponse.getJSONArray（“公告”）；
对于（int i=0；i

在更新hashmap之后调用updateList（），如

                          try {
                            JSONArray data = jsonResponse.getJSONArray("announcements");

                            for (int i = 0; i < data.length(); i++) {
                                JSONObject c = data.getJSONObject(i);

                                HashMap<String, String> map = new HashMap<String, String>();
                                map.put(TAG_ID, c.getString("announcement_id"));
                                map.put(TAG_TITLE,  c.getString("announcement_title"));
                                map.put(TAG_CONTENT, c.getString("announcement_content"));
                                map.put(TAG_DATE, c.getString("announcement_date"));
                                listArrayList.add(map);
                            }
                            updateList();
                        } catch (Exception e) {
                            e.printStackTrace();

                        }

试试看{
JSONArray data=jsonResponse.getJSONArray（“公告”）；
对于（int i=0；i

我明白了，这就是为什么有时会显示，有时不会显示的原因。谢谢，伙计，我没看到。我看到了，所以这就是为什么有时候它会出现，有时候不会。谢谢，伙计，我没看到。