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POAfter clicking the selected button,applicaton has stopped-shows logcat error
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copied!<p>In my apps,i will provide checkbox dynamically and above one button for get selected i am providing,if you click the button it has to fetch the checked data what we given in an listview.But right now after clicking button select,the application has stopped.</p> <p>Mainactivity.java</p> <pre><code>public class MainActivity extends Activity implements FetchDataListener,OnClickListener { private static final int ACTIVITY_CREATE=0; private ProgressDialog dialog; ListView lv; private List<Application> items; private Button btnGetSelected; //private ProjectsDbAdapter mDbHelper; //private SimpleCursorAdapter dataAdapter; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_list_item); //mDbHelper = new ProjectsDbAdapter(this); //mDbHelper.open(); //fillData(); //registerForContextMenu(getListView()); lv =(ListView)findViewById(R.id.list); btnGetSelected = (Button) findViewById(R.id.btnget); btnGetSelected.setOnClickListener(this); initView(); } private void initView() { // show progress dialog dialog = ProgressDialog.show(this, "", "Loading..."); String url = "http://dry-brushlands-3645.herokuapp.com/posts.json"; FetchDataTask task = new FetchDataTask(this); task.execute(url); //mDbHelper.open(); //Cursor projectsCursor = mDbHelper.fetchAllProjects(); //startManagingCursor(projectsCursor); // Create an array to specify the fields we want to display in the list (only TITLE) //String[] from = new String[]{ProjectsDbAdapter.KEY_TITLE}; // and an array of the fields we want to bind those fields to (in this case just text1) //int[] to = new int[]{R.id.text1}; /* Now create a simple cursor adapter and set it to display SimpleCursorAdapter projects = new SimpleCursorAdapter(this, R.layout.activity_row, projectsCursor, from, to); setListAdapter(projects); */ // create the adapter using the cursor pointing to the desired data //as well as the layout information /*dataAdapter = new SimpleCursorAdapter( this, R.layout.activity_row, projectsCursor, from, to, 0); setListAdapter(dataAdapter); */ } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. //getMenuInflater().inflate(R.menu.activity_main, menu); super.onCreateOptionsMenu(menu); MenuInflater mi = getMenuInflater(); mi.inflate(R.menu.activity_main, menu); return true; } @Override public boolean onMenuItemSelected(int featureId, MenuItem item) { createProject(); return super.onMenuItemSelected(featureId, item); } private void createProject() { Intent i = new Intent(this, ProjectEditActivity.class); startActivityForResult(i, ACTIVITY_CREATE); } @Override protected void onActivityResult(int requestCode, int resultCode, Intent intent) { super.onActivityResult(requestCode, resultCode, intent); initView(); } @Override public void onFetchComplete(List<Application> data) { // dismiss the progress dialog if ( dialog != null ) dialog.dismiss(); // create new adapter ApplicationAdapter adapter = new ApplicationAdapter(this, data); // set the adapter to list lv.setAdapter(adapter); lv.setOnItemClickListener(new OnItemClickListener() { @Override public void onItemClick(AdapterView<?> parent, View view, int position, long id) { CheckBox chk = (CheckBox) view.findViewById(R.id.checkbox); Application bean = items.get(position); if (bean.isSelected()) { bean.setSelected(false); chk.setChecked(false); } else { bean.setSelected(true); chk.setChecked(true); } } }); } // Toast is here... private void showToast(String msg) { Toast.makeText(this, msg, Toast.LENGTH_SHORT).show(); } @Override public void onFetchFailure(String msg) { // dismiss the progress dialog if ( dialog != null ) dialog.dismiss(); // show failure message Toast.makeText(this, msg, Toast.LENGTH_LONG).show(); } @Override public void onClick(View v) { StringBuffer sb = new StringBuffer(); // Retrive Data from list for (Application bean : items) { if (bean.isSelected()) { sb.append(bean.getContent()); sb.append(","); } } showAlertView(sb.toString().trim()); } private void showAlertView(String str) { AlertDialog alert = new AlertDialog.Builder(this).create(); if (TextUtils.isEmpty(str)) { alert.setTitle("Not Selected"); alert.setMessage("No One is Seleceted!!!"); } else { // Remove , end of the name String strContactList = str.substring(0, str.length() - 1); alert.setTitle("Selected"); alert.setMessage(strContactList); } alert.setButton("Ok", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { dialog.dismiss(); } }); alert.show(); } @Override public void onBackPressed() { AlertDialog alert_back = new AlertDialog.Builder(this).create(); alert_back.setTitle("Quit?"); alert_back.setMessage("Are you sure want to Quit?"); alert_back.setButton("No", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { dialog.dismiss(); } }); alert_back.setButton2("Yes", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { MainActivity.this.finish(); } }); alert_back.show(); } @Override public void setOnItemClickListener(OnItemClickListener onItemClickListener) { // TODO Auto-generated method stub } </code></pre> <p>This is my adapter closs,Applicationadapter.java</p> <pre><code>public class ApplicationAdapter extends ArrayAdapter<Application> { private List<Application> items; private LayoutInflater inflator; public ApplicationAdapter(Context context, List<Application> items) { super(context, R.layout.activity_row, items); this.items = items; inflator = LayoutInflater.from(getContext()); } @Override public int getCount() { return items.size(); } @Override public View getView(int position, View convertView, ViewGroup parent) { ViewHolder holder = null; //View v = convertView; if ( convertView == null ) { convertView = inflator.inflate(R.layout.activity_row, null); LayoutInflater li = LayoutInflater.from(getContext()); //convertView = inflator.inflate(R.layout.app_custom_list, null); holder = new ViewHolder(); holder.text1 = (TextView) convertView.findViewById(R.id.text1); holder.chk = (CheckBox) convertView.findViewById(R.id.checkbox); holder.chk .setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() { @Override public void onCheckedChanged(CompoundButton view, boolean isChecked) { int getPosition = (Integer) view.getTag(); items.get(getPosition).setSelected(view.isChecked()); } }); convertView.setTag(holder); convertView.setTag(R.id.text1, holder.text1); convertView.setTag(R.id.checkbox, holder.chk); }else { holder = (ViewHolder) convertView.getTag(); } Application app = items.get(position); holder.chk.setTag(position); holder.text1.setText(Html.fromHtml(items.get(position).getContent())); holder.chk.setChecked(items.get(position).isSelected()); if ( app != null ) { TextView titleText = (TextView) convertView.findViewById(R.id.titleTxt); if ( titleText != null ) titleText.setText(Html.fromHtml(app.getContent()).toString()); //titleText.setText(app.getContent()); //holder.chk.setChecked(((View) Html.fromHtml(app.getContent())).isSelected()); } return convertView; } static class ViewHolder { public TextView text1; public CheckBox chk; } //return convertView; } </code></pre> <p>Here i mention my logcat error also.</p> <pre><code>06-04 10:07:49.857: E/AndroidRuntime(2454): FATAL EXCEPTION: main 06-04 10:07:49.857: E/AndroidRuntime(2454): java.lang.NullPointerException 06-04 10:07:49.857: E/AndroidRuntime(2454): at com.example.jsonandroid.MainActivity.onClick(MainActivity.java:174) 06-04 10:07:49.857: E/AndroidRuntime(2454): at android.view.View.performClick(View.java:4202) 06-04 10:07:49.857: E/AndroidRuntime(2454): at android.view.View$PerformClick.run(View.java:17340) 06-04 10:07:49.857: E/AndroidRuntime(2454): at android.os.Handler.handleCallback(Handler.java:725) 06-04 10:07:49.857: E/AndroidRuntime(2454): at android.os.Handler.dispatchMessage(Handler.java:92) 06-04 10:07:49.857: E/AndroidRuntime(2454): at android.os.Looper.loop(Looper.java:137) 06-04 10:07:49.857: E/AndroidRuntime(2454): at android.app.ActivityThread.main(ActivityThread.java:5039) 06-04 10:07:49.857: E/AndroidRuntime(2454): at java.lang.reflect.Method.invokeNative(Native Method) 06-04 10:07:49.857: E/AndroidRuntime(2454): at java.lang.reflect.Method.invoke(Method.java:511) 06-04 10:07:49.857: E/AndroidRuntime(2454): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 06-04 10:07:49.857: E/AndroidRuntime(2454): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 06-04 10:07:49.857: E/AndroidRuntime(2454): at dalvik.system.NativeStart.main(Native Method) </code></pre> <p><strong>After clicking the btngetselected,apps has stopped</strong></p> <p>this is my Application.java</p> <pre><code>public class Application { private String content; private boolean selected; public String getContent() { return content; } public void setContent(String content) { this.content = content; } public boolean isSelected() { return selected; } public void setSelected(boolean selected) { this.selected = selected; } } </code></pre> <p>In my code,i am using asynctask for fetching data,here i attached that code also.</p> <pre><code>public class FetchDataTask extends AsyncTask<String, Void, String> { private final FetchDataListener listener; private String msg; public FetchDataTask(FetchDataListener listener) { this.listener = listener; } @Override protected String doInBackground(String... params) { if ( params == null ) return null; // get url from params String url = params[0]; try { // create http connection HttpClient client = new DefaultHttpClient(); HttpGet httpget = new HttpGet(url); // connect HttpResponse response = client.execute(httpget); // get response HttpEntity entity = response.getEntity(); if ( entity == null ) { msg = "No response from server"; return null; } // get response content and convert it to json string InputStream is = entity.getContent(); return streamToString(is); } catch ( IOException e ) { msg = "No Network Connection"; } return null; } @Override protected void onPostExecute(String sJson) { if ( sJson == null ) { if ( listener != null ) listener.onFetchFailure(msg); return; } try { // convert json string to json object JSONObject jsonObject = new JSONObject(sJson); JSONArray aJson = jsonObject.getJSONArray("post"); // create apps list List<Application> apps = new ArrayList<Application>(); for ( int i = 0; i < aJson.length(); i++ ) { JSONObject json = aJson.getJSONObject(i); Application app = new Application(); app.setContent(json.getString("content")); // add the app to apps list apps.add(app); } //notify the activity that fetch data has been complete if ( listener != null ) listener.onFetchComplete(apps); } catch ( JSONException e ) { e.printStackTrace(); msg = "Invalid response"; if ( listener != null ) listener.onFetchFailure(msg); return; } } /** * This function will convert response stream into json string * * @param is * respons string * @return json string * @throws IOException */ public String streamToString(final InputStream is) throws IOException { BufferedReader reader = new BufferedReader(new InputStreamReader(is)); StringBuilder sb = new StringBuilder(); String line = null; try { while ( (line = reader.readLine()) != null ) { sb.append(line + "\n"); } } catch ( IOException e ) { throw e; } finally { try { is.close(); } catch ( IOException e ) { throw e; } } return sb.toString(); } } </code></pre>

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