Getting issue of Network Main Thread and Null Pointer exception

Question

package com.Itattooz.Gallery;
@SuppressWarnings("unused")
public class grid_layout extends Activity {

private GridView list;
private String id_folder;
private LazyAdapter1 adapter;
private Intent intent;
private String main_folder;
private JSONArray jArray;
private String result = null;
private InputStream is = null;
private StringBuilder sb = null;
private String[] r;
boolean flag1 = false, flag2 = false, flag3 = false;
private String[] sub_folder_id;
private String[] path;
private String[] sub_folder_name;
private String[] flag;
private String previouse_folder;
private String[] url;

@Override
public void onCreate(Bundle savedInstanceState) {       
    super.onCreate(savedInstanceState);
    setContentView(R.layout.grid_layout);
    intent = getIntent();
    main_folder = intent.getStringExtra("selected_item");

    new Thread(new Runnable() {
        public void run() {
            databaseConnectivity();
        }
    }).start();


    list = (GridView) findViewById(R.id.list);
    adapter = new LazyAdapter1(this, url, sub_folder_name);
    list.setAdapter(adapter);
    list.setOnItemClickListener(grid_listener);

}

@Override
public void onDestroy() {
    list.setAdapter(null);
    super.onDestroy();
}

// djhwawd

OnItemClickListener grid_listener = new OnItemClickListener() {
    public void onItemClick(AdapterView<?> parent, View v, int position,
            long id) {
        id_folder = sub_folder_id[position];
        flag1 = true;

        TextView text = (TextView) v.findViewById(R.id.text);
        String str = (String) text.getText();
        if (flag[position].equals("X")) {

            //main_folder = main_folder + "/" + str.replace(" ", "%20");
            // int flags = Intent.FLAG_ACTIVITY_SINGLE_TOP;
            intent = new Intent(v.getContext(), grid_layout_main.class);
            intent.putExtra("folder_name",  main_folder.replace(" ", "%20") + "/" + str.replace(" ", "%20"));
            intent.putExtra("id", sub_folder_id[position]);

            startActivity(intent);
        } else {
            flag2=true;
            main_folder = main_folder + "/" + str.replace(" ", "%20");
            int flags = Intent.FLAG_ACTIVITY_SINGLE_TOP;
            intent = new Intent(v.getContext(), grid_layout.class);
            intent.setFlags(flags);
            intent.putExtra("selected_item", main_folder);
            startActivity(intent);
        }

    }
};

@Override
protected void onNewIntent(Intent intent) {
    setIntent(intent);

    new Thread(new Runnable() {
        public void run() {
            databaseConnectivity();
        }
    }).start();

    adapter = new LazyAdapter1(this, url, sub_folder_name);
    list.setAdapter(adapter);
    adapter.imageLoader.clearCache();
    adapter.notifyDataSetChanged();
    list.setOnItemClickListener(grid_listener);

}

public void databaseConnectivity() {
    HttpPost httppost = null;
    ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();

    try {

        HttpClient httpclient = new DefaultHttpClient();
        if (flag1 == false) {
            nameValuePairs
            .add(new BasicNameValuePair("folder", main_folder));
            httppost = new HttpPost(
                    "http://www.itattooz.com/android/index.php");
        } else if (flag1 == true) {
            nameValuePairs.add(new BasicNameValuePair("sub_folder_id",
                    id_folder));
            httppost = new HttpPost(
                    "http://www.itattooz.com/android/index2.php");
        }

        httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
        HttpResponse response = httpclient.execute(httppost);

        HttpEntity entity = response.getEntity();

        is = entity.getContent();

    } catch (Exception e) {
        Log.e("log_tag", "Error in http connection" + e.toString());

    }

    try {
        BufferedReader reader = new BufferedReader(new InputStreamReader(
                is, "iso-8859-1"), 8);
        StringBuilder sb = new StringBuilder();
        String line = null;
        while ((line = reader.readLine()) != null) {
            sb.append(line + "\n");
        }
        is.close();

        result = sb.toString();

    } catch (Exception e) {

        Log.e("log_tag", "Error converting result " + e.toString());
    }
    String rt;
    try {
        jArray = new JSONArray(result);
        path = new String[jArray.length()];
        sub_folder_id = new String[jArray.length()];
        sub_folder_name = new String[jArray.length()];
        flag = new String[jArray.length()];
        url = new String[jArray.length()];
        JSONObject json_data = null;
        for (int i = 0; i < jArray.length(); i++) {
            json_data = jArray.getJSONObject(i);
            sub_folder_id[i] = json_data.getString("id");
            sub_folder_name[i] = json_data.getString("folder");
            flag[i] = json_data.getString("flag");
            path[i] = json_data.getString("path");

            rt = "http://www.itattooz.com/itattooz/"
                    + main_folder.replace(" ", "%20") + "/"
                    + sub_folder_name[i].replace(" ", "%20")
                    + "/cover_image/" + path[i].replace(" ", "%20");

            url[i] = rt;
        }
    } catch (JSONException e1) {
        Toast.makeText(getBaseContext(), "No Image Found",
                Toast.LENGTH_LONG).show();
    } catch (ParseException e1) {
        e1.printStackTrace();
    }

}
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
    if ((keyCode == KeyEvent.KEYCODE_BACK)) {
        onResume();
        Log.d(this.getClass().getName(), "back button pressed");

    }
    return super.onKeyDown(keyCode, event);
}
@Override
public void onResume() { // After a pause OR at startup
    super.onResume();

    // Refresh your stuff here
}

@Override
protected void onPause() {

    super.onPause();
}

}

Hello Above is my code for a Gallery view as a grid layout ..

I researched a lot on net and got to know I should use AsyncTask for what I am trying to achieve .. Here Are few problems i am facing

I am doing something on Main thread
I want to change it to AsyncTask..

Don't know what should I do exactly to get rid of this issue.. Please Help...

using a thread is fine but if you get `NetworkOnMainThreadException` it means you are running network related operation on the ui thread. — Raghunandan, Jul 02 '13 at 10:49
it seams like you're not getting how threads are working ... Thread.start is not blocking so fx `url` in `adapter = new LazyAdapter1(this, url, sub_folder_name);` may or may be not null — Selvin, Jul 02 '13 at 10:56

score 0 · Answer 1 · edited May 23 '17 at 12:21

use the asyncTask to handle this exception.

Please see the android developer Link

or you can see the stackoverflow Accepted answer related to this Link HERE

For exmp

 class YourTask extends AsyncTask<URL, Integer, String> {
     protected String doInBackground(URL... urls) {
         // Fetch Data (Task A)
         return "Result";
     }

     protected void onProgressUpdate(Integer... progress) {
         // Show progress
     }

     protected void onPostExecute(String result) {
         // Show UI after complete (Task B)
     }
}

score 0 · Answer 2 · edited Jul 02 '13 at 11:06

0

Use Async Task

or

   if (android.os.Build.VERSION.SDK_INT > 9)  {  
   StrictMode.ThreadPolicy policy = new  StrictMode.ThreadPolicy.Builder().permitAll().build();    
   StrictMode.setThreadPolicy(policy);  
    }

edited Jul 02 '13 at 11:06

Tarsem Singh

14,139
7
51
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answered Jul 02 '13 at 10:56

ramkumar5035

361
1
4
11

Tarsem Singh · Answer 3 · 2013-07-02T11:13:40.880

use AsyncTask

or

add below code in your onCreate() method before thread starts to disable the strict mode using following code:

this is not the solution but avoids network IO on main thread so i recommend AsyncTask

    if (android.os.Build.VERSION.SDK_INT > 9) {
        StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder()
                .permitAll().build();
        StrictMode.setThreadPolicy(policy);
    }

also check internet permission in AndroidManifest.xml file

   <uses-permission android:name="android.permission.INTERNET"/>

Getting issue of Network Main Thread and Null Pointer exception

3 Answers3