如何通过JSON获取实时更新到ListView

Question

我找不到通过JSON实时更新到列表视图的方法。

我的活动是从网页请求JSON数据，代码是：

public class Second extends Activity {

    static final String Li_nk = "LinkName:";
    static final String Image_name = "ImageName:";
    ListView list;
    public final static String AUTH = "authentication";
    static final String KEY_THUMB_URL = "thumb_image"; // Uri.decode("http://zeesms.info/android_app_images/Koala.jpg");

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        Intent i2 = getIntent();
        String wrd = i2.getStringExtra("entrd");
        Log.v("keyis", wrd);

        // if(wrd.equalsIgnoreCase("test")){
        JSONObject j2 = JSONfunctions.getJSONfromURL("/webservice_search.php?keyword=" + wrd + "&format=json");

        ArrayList<HashMap<String, String>> mylist = new ArrayList<HashMap<String, String>>();
        try {
            JSONArray jray = j2.getJSONArray("listings");
            for (int i = 0; i < jray.length(); i++) {
                Log.v("state", "json data being read");
                JSONObject j3 = jray.getJSONObject(i);
                String first = j3.getString("listing");
                Log.v("sublist", first);
                JSONObject j4 = j3.getJSONObject("listing");
                String sec = j4.getString("links");

                int maxLength = (sec.length() < 30) ? sec.length() : 27;
                sec.substring(0, maxLength);
                String cutsec = sec.substring(0, maxLength);
                Log.v("links are", cutsec);
                String img = j4.getString("image_name");
                Log.v("image name is ", img);
                // Uri
                // dimg=Uri.parse("http://zeesms.info/android_app_images/Koala.jpg");
                HashMap<String, String> map = new HashMap<String, String>();

                map.put("Id", String.valueOf(i));
                map.put(Li_nk, cutsec);
                map.put(Image_name, j4.getString("image_name"));

                map.put(KEY_THUMB_URL, "http://zeesms.info/android_app_images/" + img);
                mylist.add(map);

            }

        }
        catch (JSONException e) {
            alertbox();
            Log.e("loG_tag", "Error parsing" + e.toString());
        }

        list = (ListView) findViewById(R.id.lv1);
        this.list.setEmptyView(findViewById(R.id.empty));
        list.setOnItemClickListener(new AdapterView.OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {

                // Toast.makeText(getApplicationContext(),"Click ListItem Number "
                // + position, Toast.LENGTH_LONG).show();
                Intent myIntent = new Intent(Intent.ACTION_VIEW, Uri.parse("http://www.riffre.com/"));
                startActivity(myIntent);
            }

        });
        LazyAdapter adapter = new LazyAdapter(this, mylist);

        list.setAdapter(adapter);
        list.setItemsCanFocus(false);

        // }
        /*
         * else{ alertbox(); }
         */

    }

    /*
     * public void register(View view) { Log.w("C2DM",
     * "start registration process"); Intent intent = new
     * Intent("com.google.android.c2dm.intent.REGISTER");
     * intent.putExtra("app", PendingIntent.getBroadcast(this, 0, new
     * Intent(), 0)); // Sender currently not used intent.putExtra("sender",
     * "nonsenses@gmail.com"); startService(intent); }
     * 
     * public void showRegistrationId(View view) { SharedPreferences prefs =
     * PreferenceManager .getDefaultSharedPreferences(this); String string =
     * prefs.getString(AUTH, "n/a"); Toast.makeText(this, string,
     * Toast.LENGTH_LONG).show(); Log.d("C2DM RegId", string);
     * 
     * }
     */
    public void alertbox() {

        new AlertDialog.Builder(this).setMessage("Invalid Keyword,No Results found").setTitle("Alert").setCancelable(true).setPositiveButton(android.R.string.ok, new DialogInterface.OnClickListener() {

            public void onClick(DialogInterface dialog, int whichButton) {

                finish();

            }
        }).show();
    }
}

我正在使用一个自定义适配器，其代码如下：

public class LazyAdapter extends BaseAdapter {
    private Activity activity;
    private ArrayList<HashMap<String, String>> data;
    private static LayoutInflater inflater=null;
    public ImageLoader imageLoader; 


    public LazyAdapter(Activity a, ArrayList<HashMap<String, String>> d) {
        activity = a;
        data=d;
        inflater = (LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        imageLoader=new ImageLoader(activity.getApplicationContext());
    }

    @Override
    public int getCount() {
        // TODO Auto-generated method stub
        return data.size();
    }

    @Override
    public Object getItem(int position) {
        // TODO Auto-generated method stub
        return position;
    }

    @Override
    public long getItemId(int position) {
        // TODO Auto-generated method stub
        return position;
    }


    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View vi=convertView;
        if(convertView==null)

            vi = inflater.inflate(R.layout.custom_row_view1, null);

        TextView title = (TextView)vi.findViewById(R.id.linkname); // merchnts name
        TextView artist = (TextView)vi.findViewById(R.id.imagename); // address
        //TextView duration = (TextView)vi.findViewById(R.id); // distance
       ImageView thumb_image=(ImageView)vi.findViewById(R.id.mClogo); // logo

        HashMap<String, String> jsn = new HashMap<String, String>();
        jsn = data.get(position);

        // Setting all values in listview
       title.setText(jsn.get(Second.Li_nk));
       artist.setText(jsn.get(Second.Image_name));
        //duration.setText(song.get(CustomizedListView.KEY_DURATION));
        imageLoader.DisplayImage(jsn.get(Second.KEY_THUMB_URL), thumb_image);
        return vi;
    }
}

我想要的是应用程序每分钟左右用数据更新listview。列表中的最新条目也应放在最前面。

最好的方法是什么？

Answer 1

将您的 JSON 解析代码放在try..catch一个单独的函数中，而不是在onCreate().

因此每分钟都可以轻松调用该部分。假设函数名称每次LoadData()还添加一行来更新适配器/列表。adapter.notifyDataSetChanged()

现在在 onCreate() 中，编写此代码以每隔一分钟调用该函数，

    final Handler handler = new Handler();
    Runnable runable = new Runnable() {

        @Override
        public void run() {

            //call the function
            LoadData();
            //also call the same runnable
            handler.postDelayed(this, 1000);
        }
    };
    handler.postDelayed(runable, 1000);

现在解决第二个问题，在顶部添加新数据..

我现在只想着写一个循环，在调用适配器通知更改之前将其添加到您的函数中，例如

     ArrayList<HashMap<String,String>> mylist = new  ArrayList<HashMap<String,String>>(); 
     ArrayList<HashMap<String,String>> mylistTemp = new  ArrayList<HashMap<String,String>>();
     for(int i = mylist.size()-1 ; i >=0;i--)
     {
         mylistTemp.add(mylist.get(i));
     }
     mylist = mylistTemp;