Refreshing screen which uses json in android

问题:

I have a module in my application which uses json.

The json gets updated always.

Here i want to refresh the screen as new data arrives.

Is there any method for this ?

I want to refresh the screen as new data arrives or once in every 5 seconds or something(a fixed amount of time).How to do this ?

I simply used a local json file to test this.

I just need the code for refreshing.

This is my code for json parsing :

public class MainActivity extends Activity  {     String myjsonstring;       ArrayList<Data> web = new ArrayList<Data>();       @Override     protected void onCreate(Bundle savedInstanceState)      {         super.onCreate(savedInstanceState);         setContentView(R.layout.main);           JsonParser();           // Try to parse JSON         try {               JSONObject jsonObjMain = new JSONObject(myjsonstring);             JSONArray jsonArray = jsonObjMain.getJSONArray("pgm");              for (int i = 0; i < jsonArray.length(); i++) {                  // Creating JSONObject from JSONArray                 JSONObject jsonObj = jsonArray.getJSONObject(i);                  // Getting data from individual JSONObject                  Data data = new Data(jsonObj.getString("name") , jsonObj.getString("viewers"));                  web.add(data);             }              final customtest1 adapter = new customtest1(MainActivity.this,R.layout.list_single,web);              ListView list = (ListView)findViewById(R.id.list);             list.setAdapter(adapter);              list.setOnItemClickListener(new AdapterView.OnItemClickListener()              {                  @Override                 public void onItemClick(AdapterView<?> parent, View view,                         int position, long id) {                      Toast.makeText(MainActivity.this, "Test.........", Toast.LENGTH_SHORT).show();                      adapter.notifyDataSetChanged();                 }              });          } catch (JSONException e) {             // TODO Auto-generated catch block             e.printStackTrace();         }         }      private void JsonParser()      {         // Reading text file from assets folder         StringBuffer sb = new StringBuffer();         BufferedReader br = null;         try {             br = new BufferedReader(new InputStreamReader(getAssets().open(                     "main.json")));             String temp;             while ((temp = br.readLine()) != null)                 sb.append(temp);         } catch (IOException e) {             e.printStackTrace();         } finally {             try {                 br.close(); // stop reading             } catch (IOException e) {                 e.printStackTrace();             }         }          myjsonstring = sb.toString();      }     } 

回答1:

Do this. create a class

public class Data { String name =""; String viewers ="";  public Data(String n,String v) { name = n; viewers=v; }    } 

then in MainActivity create only single arraylist with type Data

ArrayList<Data> web = new ArrayList<Data>(); 

and then parse your json like

// Creating JSONObject from String         JSONObject jsonObjMain = new JSONObject(myjsonstring);          // Creating JSONArray from JSONObject         JSONArray jsonArray = jsonObjMain.getJSONArray("pgm");          // JSONArray has four JSONObject         for (int i = 0; i < jsonArray.length(); i++) {              // Creating JSONObject from JSONArray             JSONObject jsonObj = jsonArray.getJSONObject(i);              // Getting data from individual JSONObject              Data data = new Data(jsonObj.getString("name") , jsonObj.getString("viewers"));              web.add(data); 

now instead of passing two array list to your custom adapter , pass only single arraylist i.e web

customtest adapter = new customtest(MainActivity.this,R.layout.list_single,web);  ListView list = (ListView)findViewById(R.id.list); list.setAdapter(adapter); 

in your customtest class , inside getview when you will bind data, you will do

Data dt = web.get(position); String name = dt.name; String viewers = dt.viewers; 

and then do what you were doing before.

and after all this, now ehnever you want to update your list simply call

adapter.notifyDataSetChanged(); 

your customtest class now will be like

    public class customtest extends ArrayAdapter<Data>{  Context context;  int layoutResourceId;     ArrayList<Data> data = null;  public customList(Context context, int layoutResourceId, ArrayList<Data> data) {     super(context, layoutResourceId, data);     this.layoutResourceId = layoutResourceId;     this.context = context;     this.data = data; }  @Override public View getView(int position, View convertView, ViewGroup parent) {     View row = convertView;     CustomHolder holder = null;      if(row == null)     {         LayoutInflater inflater = ((Activity)context).getLayoutInflater();         row = inflater.inflate(layoutResourceId, parent, false);          holder = new CustomHolder();         holder.txtName = (TextView)row.findViewById(R.id.txtName);   //this is id of textview where you want to set name         holder.txtViewers = (TextView)row.findViewById(R.id.txtViewers);     //this is id of textview where you want to set viewers          row.setTag(holder);     }     else     {         holder = (CustomHolder)row.getTag();     }      Data dt = data.get(postition);     holder.txtName.setText(dt.name);     holder.txtViewers.setText(dt.viewers);          return row;     }          static class CustomHolder         {             TextView txtName;             TextView txtViewers;         }     } 

//////////////////////////////////////////////////////////////////////////////////////////

new Thread(){  public void run() { While(true) { Thread.sleep(3000); jsonParse(); //this is your method for parsing json } }  }.start(); 

文章来源: Refreshing screen which uses json in android