Question

这里是我之前的问题How to Print Message when Json Response has no fileds? Toast工作正常，但如果我的回复显示没有带数组的文件，如果我想使用textview而不是Toast怎么办？任何人都可以帮助我吗？ enter image description here

public class MessageSent extends ListActivity{

    private ProgressDialog pDialog;
    JSONArray msg=null;
    private TextView nomsg;

    private ListView listview;

    private ArrayList<HashMap<String,String>> aList;
    private static String MESSAGE_URL = "";
    private static final String MESSAGE_ALL="msg";
    private static final String MESSAGEUSER_ID="msg_user_id";
    private static final String MESSAGE_NAME="name";
    private static final String MESSAGE_PROFILE="profile_id";
    private static final String MESSAGE_IMAGE="image";
    private static final String MESSAGE_CAST="cast";
    private static final String MESSAGE_AGE="age";
    private static final String MESSAGE_LOCATION="location";
    private CustomAdapterMessage adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.list_view_msgsent);
        nomsg=(TextView)findViewById(R.id.no_message);
        String strtexts = getIntent().getStringExtra("id");
        System.out.println("<<<<<<<< id : " + strtexts);
        MESSAGE_URL = "xxxxx"+strtexts;

        // listview=(ListView)findViewById(R.id.list);

        //ListView listview = this.getListView();

        ListView listview = (ListView)findViewById(android.R.id.list);

        new LoadAlbums().execute();


            }
        });
    }

    class LoadAlbums extends AsyncTask>> {

        /**
         * Before starting background thread Show Progress Dialog
         * */

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            pDialog = new ProgressDialog(MessageSent.this);
            pDialog.setMessage("Loading...");
            pDialog.setIndeterminate(false);
            pDialog.setCancelable(false);
            pDialog.show();
        }

        protected ArrayList<HashMap<String,String>> doInBackground(String... args) {
            ServiceHandler sh = new ServiceHandler();

            // Making a request to url and getting response
            ArrayList<HashMap<String,String>> data = new ArrayList<HashMap<String, String>>();
            String jsonStr = sh.makeServiceCall(MESSAGE_URL, ServiceHandler.GET);

            Log.d("Response: ", "> " + jsonStr);

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

                    // Getting JSON Array node
                    msg = jsonObj.getJSONArray(MESSAGE_ALL);

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

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

                        // adding each child node to HashMap key => value
                        map.put(MESSAGEUSER_ID ,c.getString(MESSAGEUSER_ID));
                        map.put(MESSAGE_NAME,c.getString(MESSAGE_NAME));
                        map.put(MESSAGE_PROFILE, c.getString(MESSAGE_PROFILE));
                        map.put(MESSAGE_IMAGE, c.getString(MESSAGE_IMAGE));
                        map.put(MESSAGE_CAST, c.getString(MESSAGE_CAST));
                        map.put(MESSAGE_AGE, c.getString(MESSAGE_AGE)+" years");
                        map.put(MESSAGE_LOCATION, c.getString(MESSAGE_LOCATION));

                        // adding HashList to ArrayList
                        data.add(map);
                    }
                } catch (JSONException e) {
                    e.printStackTrace();
                }
            } else {
                Log.e("ServiceHandler", "Couldn't get any data from the url");
            }

            return data;
        }

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

            // dismiss the dialog after getting all albums
            if (pDialog.isShowing())
                pDialog.dismiss();

            if(msg == null || msg.length() == 0) { 
                //Toast.makeText(getApplicationContext(), "No response", Toast.LENGTH_LONG).show
                nomsg.setText("No Message Found");
                //nomsg.setBackgroundDrawable(R.drawable.borders);
            }

            if(aList == null) {
                aList = new ArrayList<HashMap<String, String>>();
                aList.addAll(result);
                adapter = new CustomAdapterMessage(getBaseContext(), result);
                setListAdapter(adapter);
            } else {
                aList.addAll(result);
                adapter.notifyDataSetChanged();
            }
        }

    }
}

Answer 1

尝试这种方式：

protected void onPostExecute(Void result) {
    super.onPostExecute(result);

    if (pDialog.isShowing())
        pDialog.dismiss();

    if(contacts == null || contacts.length() <= 0){
        yourTextView.setText("No Data");   
    }
 }

Answer 2

因为看起来您在设置应用时遇到了困惑。让我解释几件事情，并为您提供一些示例代码。

使用AsynTask？

AsyncTask enables proper and easy use of the UI thread. This class allows to perform background operations and publish results on the UI thread without having to manipulate threads and/or handlers.

但是在后台线程中工作时，您需要在UI中执行一些操作。在这种情况下，您可以使用

1. onPreExecute(), invoked on the UI thread before the task is executed. This step is normally used to setup the task, for instance by showing a progress bar in the user interface.

2. onPostExecute(Result), invoked on the UI thread after the background computation finishes. The result of the background computation is passed to this step as a parameter.

在特定情况下，如果要在操作后设置值，则必须使用AsynTask的后一个方法。

参考您所遵循的示例的相同代码，

//MainActivity.java
public class MainActivity extends ListActivity {

    TextView yourTextView;

     @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        .
        .
        //change the ID in this line from what you are using
        yourTextView = (TextView) findViewByID(R.id.id_in_activity_main);
        .
        .

        // Calling async task to get json
        new GetContacts().execute();
    }

    /**
     * Async task class to get json by making HTTP call
     * */
    private class GetContacts extends AsyncTask<Void, Void, Void> {

        @Override
        protected void onPreExecute() {
            .
            .
        }

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

        protected void onPostExecute(Void result) {
            super.onPostExecute(result);

            if (pDialog.isShowing())
                pDialog.dismiss();

            if(contacts == null || contacts.length() <= 0){
                yourTextView.setText("No Data");   
            }
         }
     }
 }

如果条件满足，如何设置textview？

2 个答案: