使用AsyncTask在ListView中顯示數據

Question

我需要我一點幫助。 我需要使用asynctask在ListView中顯示數據。 但是我不知道我是如何成為Android編程的新手……非常感謝您的幫助。

public class Main extends ListActivity {
Button buttonbg;   
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
   setContentView(R.layout.listplaceholder);

    ArrayList<HashMap<String, String>> mylist = new ArrayList<HashMap<String, String>>();

    JSONObject json = JSONfunctions.getJSONfromURL("http://10.10.10.10/data.php");

    try{

        JSONArray  ip = json.getJSONArray("ip");

        for(int i=0;i<ip.length();i++){                     
            HashMap<String, String> map = new HashMap<String, String>();    
            JSONObject e = ip.getJSONObject(i);

            map.put("id",  String.valueOf(i));
            map.put("data1", e.getString("date"));
            map.put("data2", "Location:" +  e.getString("location") + "   Status:" + e.getString("status"));
            mylist.add(map);            
        }       
    }catch(JSONException e)        {
         Log.e("log_tag", "Error parsing data "+e.toString());
    }

    ListAdapter adapter = new SimpleAdapter(this, mylist , R.layout.main, 
                    new String[] { "data1", "data2" }, 
                    new int[] { R.id.item_title, R.id.item_subtitle });

    setListAdapter(adapter);

    final ListView lv = getListView();
    lv.setTextFilterEnabled(true);

}}

Answer 1

嘗試這個

new MyAsyncTask.execute("http://10.10.10.10/data.php");

將任務聲明為

class MyAsyncTask extends AsyncTask<String, Integer, ArrayList<HashMap<String, String>> > {

    ArrayList<HashMap<String, String>> mylist = new ArrayList<HashMap<String, String>>();

    @Override
    protected ArrayList<HashMap<String, String>> doInBackground(String... params) {

        JSONObject json = JSONfunctions.getJSONfromURL(params[0]);

        try {
            JSONArray  ip = json.getJSONArray("ip");

            for (int i=0;i<ip.length();i++) {                     
                HashMap<String, String> map = new HashMap<String, String>();    
                JSONObject e = ip.getJSONObject(i);

                map.put("id",  String.valueOf(i));
                map.put("data1", e.getString("date"));
                map.put("data2", "Location:" +  e.getString("location") + "   Status:" + e.getString("status"));
                mylist.add(map);            
            } 
            return mylist
        } catch (JSONException e) {
            Log.e("log_tag", "Error parsing data "+e.toString());
        }
        return null;
    }

    @Override
    protected void onPostExecute(ArrayList<HashMap<String, String>> result) {
        ListAdapter adapter = new SimpleAdapter(YourActivity.this, result , R.layout.main, 
                new String[] { "data1", "data2" }, 
                new int[] { R.id.item_title, R.id.item_subtitle });
        YourActivity.this.setListAdapter(adapter); // If Activity extends ListActivity
        final ListView lv = getListView();
        lv.setTextFilterEnabled(true);

    }

希望能幫助到你。

Answer 2

不要在onCreate（）中下載任何數據-如果花費的時間太長，則會收到ANR異常（活動無響應）。 您應該在問題中使用AsyncTask。 對於AsyncTask，您在android網站上有一個很好的示例：

http://developer.android.com/reference/android/os/AsyncTask.html

您應該將JSONfunctions.getJSONfromURL（）放入doInBackground（）

以及onPostExecute（）下面的所有內容