Question

I have a list view of places in which I get from a database, I made an OnItemLongClickListener on the items, after the long click an alert dialog is activated with some information, in the message body, which I get from the database concerning the item clicked. The dialog has 3 buttons (Call, Map it and View Photo) which are working fine. The dialog works for the first 8 items and then the dialog doesn’t open and the application force closes for the rest of the items I don’t know why!

Can you please help me?

Here is the code in which the list of all Hotels is displayed:

List<Hotel> values = datasource.getAllHotels();
            if (values.isEmpty())
            {
                Toast.makeText(this, "No results found!", Toast.LENGTH_LONG).show();
                Intent i1 = new Intent(hotelSearchList.this, hotelSearch.class);
                startActivity(i1);
            }
            ArrayAdapter<Hotel> adapter = new ArrayAdapter<Hotel>(this,
                    android.R.layout.simple_list_item_1, values);
            setListAdapter(adapter);
            ListView lv = getListView();
            lv.setOnItemLongClickListener(this);

And this is the code for the onItemLongClickListener:

public boolean onItemLongClick(final AdapterView<?> parent, final View view, int position,
        long id) {
    // TODO Auto-generated method stub
    String hotelName = (String) ((TextView)parent.getChildAt(position)).getText();
    final List<Hotel> location = datasource.getHotelLocation(hotelName);
    String loc = "Location: " + TextUtils.join(", ", location);
    List<Hotel> address = datasource.getHotelAddress(hotelName);
    String add = "Address: " + TextUtils.join(", ", address);
    List<Hotel> rating = datasource.getHotelRating(hotelName);
    String rat = "Rating: " + TextUtils.join(", ", rating);
    List<Hotel> phone = datasource.getHotelPhone(hotelName);
    final String phoneN = "Phone: " + TextUtils.join(", ", phone);
    List<Hotel> latitude = datasource.getHotelLat(hotelName);
    final String lat = latitude.get(0).toString();
    List<Hotel> longitude = datasource.getHotelLon(hotelName);
    final String lon = longitude.get(0).toString();
    List<Hotel> photo = datasource.getHotelPhoto(hotelName);
    final String pho = photo.get(0).toString();
    //Toast.makeText(hotelSearchList.this, "The hotel clicked is " + hotelName, Toast.LENGTH_LONG).show();
    AlertDialog.Builder builder = new AlertDialog.Builder(this);
    builder.setTitle("Information About " + hotelName);
    builder.setMessage(loc + "\n" + add + "\n" + rat + "\n" + phoneN + "\n");

    builder.setPositiveButton("Call", new DialogInterface.OnClickListener() {

        public void onClick(DialogInterface dialog, int which) {
            // TODO Auto-generated method stub
            Intent i = new Intent(Intent.ACTION_DIAL, Uri.parse("tel:" + phoneN));
            startActivity(i);
        }
    });
    builder.setNegativeButton("View Photo", new DialogInterface.OnClickListener() {

        public void onClick(DialogInterface dialog, int which) {
            // TODO Auto-generated method stub
            Intent i = new Intent(hotelSearchList.this, imageV.class);
            i.putExtra("photo", pho);
            startActivity(i);
        }
    });
    builder.setNeutralButton("Map it", new DialogInterface.OnClickListener() {

        public void onClick(DialogInterface arg0, int arg1) {
            // TODO Auto-generated method stub
            Intent i = new Intent(hotelSearchList.this, mapActivity.class);
            i.putExtra("latitude", lat);
            i.putExtra("longitude", lon);
            startActivity(i);
        }
    });

    builder.setCancelable(true);
    builder.show();
    return false;
}

Here is the log cat:

04-28 19:47:15.159: E/AndroidRuntime(384): FATAL EXCEPTION: main
04-28 19:47:15.159: E/AndroidRuntime(384): java.lang.NullPointerException
04-28 19:47:15.159: E/AndroidRuntime(384):  at egypt.interfaceAct.touristicASearchList.onItemLongClick(touristicASearchList.java:134)
04-28 19:47:15.159: E/AndroidRuntime(384):  at android.widget.AbsListView.performLongPress(AbsListView.java:1753)
04-28 19:47:15.159: E/AndroidRuntime(384):  at android.widget.AbsListView.access$600(AbsListView.java:72)
04-28 19:47:15.159: E/AndroidRuntime(384):  at android.widget.AbsListView$CheckForLongPress.run(AbsListView.java:1711)
04-28 19:47:15.159: E/AndroidRuntime(384):  at android.os.Handler.handleCallback(Handler.java:587)
04-28 19:47:15.159: E/AndroidRuntime(384):  at android.os.Handler.dispatchMessage(Handler.java:92)
04-28 19:47:15.159: E/AndroidRuntime(384):  at android.os.Looper.loop(Looper.java:123)
04-28 19:47:15.159: E/AndroidRuntime(384):  at android.app.ActivityThread.main(ActivityThread.java:4627)
04-28 19:47:15.159: E/AndroidRuntime(384):  at java.lang.reflect.Method.invokeNative(Native Method)
04-28 19:47:15.159: E/AndroidRuntime(384):  at java.lang.reflect.Method.invoke(Method.java:521)
04-28 19:47:15.159: E/AndroidRuntime(384):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
04-28 19:47:15.159: E/AndroidRuntime(384):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
04-28 19:47:15.159: E/AndroidRuntime(384):  at dalvik.system.NativeStart.main(Native Method)

Answer 1

This is an excellent time to set some breakpoints in onItemLongClick() and use your debugger. It will help you find the null value or at least find the line where it crashes.

I’m willing to guess that the number of times the dialog opens is irrelevant, I assume your 8th entry that has a dud. If you click the 8th entry first does it still crash? If so, you check your database, does the row for the 8th hotelName have all of the fields that you request or does one (or more) columns have a null value?

Addition

When the list has scrolled and you use this line:

String hotelName = (String) ((TextView)parent.getChildAt(position)).getText();

The position is out of bounds which returns null causing your NullPointerException since the only children of parent are the visible ones, instead try a faster, simpler approach:

String hotelname = ((TextView) view).getText().toString();