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POResetting value of NumberPicker inside ListView item
 

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  1. POResetting value of NumberPicker inside ListView item
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    <p>I have a <code>ListView</code> activity that has a <code>NumberPicker</code> view on each item in the list. The user can use this picker to add/remove items. It is working however the issue I have is that when I resume the <code>ListView</code> activity the values are still at the chosen values when I would like them to be set to 0. </p> <p>Is there any way I can do this? So far I have done the following inside my <code>MenuItemArrayAdapter</code> class I add a method to reset the number picker. </p> <pre><code>public class MenuItemArrayAdapter extends ArrayAdapter&lt;MenuItem&gt;{ private List&lt;MenuItem&gt; menuItems; private List&lt;MenuItem&gt; order; private static NumberPicker np; private TextView price; private double amount = 0.0; private double total = 0.0; //Constructor public MenuItemArrayAdapter(Context context, List&lt;MenuItem&gt; menuItems, TextView price) { super(context, R.layout.menuitem_row, menuItems); this.menuItems = menuItems; this.price = price; order = new ArrayList&lt;MenuItem&gt;(); } public MenuItemArrayAdapter(Context context){ super(context, R.layout.menuitem_row); } //get views public View getView(final int position, View convertView, ViewGroup parent){ View v = convertView; if(v == null){ LayoutInflater vi = (LayoutInflater) getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE); v = vi.inflate(R.layout.menuitem_row, null); v.setFocusable(true); } //assign values to view final MenuItem item = this.menuItems.get(position); TextView nameView = (TextView) v.findViewById(R.id.item_name); final TextView priceView = (TextView) v.findViewById(R.id.item_price); nameView.setText(item.getName() + " "); priceView.setText("€"+ String.valueOf(item.getPrice())); //number picker np = (NumberPicker)v.findViewById(R.id.numpick); np.setMaxValue(20); np.setMinValue(0); np.setValue(0); np.setFocusable(false); //calculation occurs when values are changed... np.setOnValueChangedListener( new OnValueChangeListener() { public void onValueChange(NumberPicker picker, int oldVal, int newVal) { Toast.makeText(picker.getContext(), "dish: " + item.getName() + " amount: " + picker.getValue(), Toast.LENGTH_SHORT).show(); Toast.makeText(picker.getContext(), "new Value: " + newVal + " old Value: " + oldVal, Toast.LENGTH_SHORT).show(); // amount += item.getPrice() * picker.getValue(); if(newVal &gt; oldVal){ total = (item.getPrice() * newVal) - item.getPrice() * oldVal; //add to order order.add(item); amount += total; Toast.makeText(picker.getContext(), "ADDED TO ORDER: " + item.getName(), Toast.LENGTH_SHORT).show(); } if(newVal &lt; oldVal){ total = (item.getPrice() * oldVal) - item.getPrice() * newVal; //remove from order order.remove(item); amount -= total; Toast.makeText(picker.getContext(), "REMOVED FROM ORDER: " + item.getName(), Toast.LENGTH_SHORT).show(); } price.setText("€" + String.valueOf(amount)); } }); return v; } public List&lt;MenuItem&gt; getOrder() { return order; } public void resetNumberPicker(){ np.setValue(0); } </code></pre> <p>}</p> <p>I then call this method in the ListView activity:</p> <pre><code> protected void onPostExecute(Boolean result) { super.onPostExecute(result); if(result){ pDialog.dismiss(); adapter = new MenuItemArrayAdapter(StartersActivity.this, starters, price); adapter.resetNumberPicker(); StartersActivity.this.setListAdapter(adapter); } } </code></pre> <p>but i get this error:</p> <p><strong>FATAL EXCEPTION: main java.lang.NullPointerException at com.example.waitron5.MenuItemArrayAdapter.resetNumberPicker(MenuItemArrayAdapter.java:104)</strong></p> <p>this is the logcat:</p> <pre><code>FATAL EXCEPTION: main 01-21 18:04:40.053: E/AndroidRuntime(18291): java.lang.NullPointerException 01-21 18:04:40.053: E/AndroidRuntime(18291): at com.example.waitron5.MenuItemArrayAdapter.resetNumberPicker(MenuItemArrayAdapter.java:104) 01-21 18:04:40.053: E/AndroidRuntime(18291): at com.example.waitron5.StartersActivity$HTTPTask.onPostExecute(StartersActivity.java:215) 01-21 18:04:40.053: E/AndroidRuntime(18291): at com.example.waitron5.StartersActivity$HTTPTask.onPostExecute(StartersActivity.java:1) 01-21 18:04:40.053: E/AndroidRuntime(18291): at android.os.AsyncTask.finish(AsyncTask.java:631) 01-21 18:04:40.053: E/AndroidRuntime(18291): at android.os.AsyncTask.access$600(AsyncTask.java:177) 01-21 18:04:40.053: E/AndroidRuntime(18291): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644) 01-21 18:04:40.053: E/AndroidRuntime(18291): at android.os.Handler.dispatchMessage(Handler.java:99) 01-21 18:04:40.053: E/AndroidRuntime(18291): at android.os.Looper.loop(Looper.java:137) 01-21 18:04:40.053: E/AndroidRuntime(18291): at android.app.ActivityThread.main(ActivityThread.java:5039) 01-21 18:04:40.053: E/AndroidRuntime(18291): at java.lang.reflect.Method.invokeNative(Native Method) 01-21 18:04:40.053: E/AndroidRuntime(18291): at java.lang.reflect.Method.invoke(Method.java:511) 01-21 18:04:40.053: E/AndroidRuntime(18291): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 01-21 18:04:40.053: E/AndroidRuntime(18291): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 01-21 18:04:40.053: E/AndroidRuntime(18291): at dalvik.system.NativeStart.main(Native Method) </code></pre> <p>The error is occuring at this line 104:</p> <pre><code>np.setValue(0); </code></pre> <p>I realise that it is perhaps because I am not getting a reference to the <code>NumberPicker</code> np. But How can I fix my code so that this will not return an NPE? </p>
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    1. COhave u tried to check np for NULL before calling setValue ?
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    2. COI did this `if(np!=null)np.setValue(0)` and that stopped the crashing, however the issue is that when the activity is reloaded the values in the number picker have not been reset
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    3. CO"activity is reloaded" means starting it again ? then u will need to call resetNumberPicker method in Activity on Resume
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