AlertDialog Box is not working if there is no internet connection

Question

I am doing a google map project. My requirement is if I press a button in the present activity, it will take to google map activity else it should show the alert dialog showing the network not available message. The app crashes if there is no network. The Following is the code:

public class HomeFragment extends Fragment {
          protected static final Context Context = null;

    // flag for Internet connection status
    Boolean isInternetPresent = false;

    // Connection detector class
    ConnectionDetector cd;      public HomeFragment(){}

        ImageButton button;         @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {

        View rootView = inflater.inflate(R.layout.fragment_home, container, false);

        return rootView;
    }

    @Override   public void onActivityCreated(Bundle savedInstanceState) {      // TODO Auto-generated method stub      super.onActivityCreated(savedInstanceState);

        // creating connection detector class instance
        cd = new ConnectionDetector( getActivity());


        button = (ImageButton) getActivity().findViewById(R.id.button);
                button.setOnClickListener(new OnClickListener() {
                        @Override           public void onClick(View v) {
                // TODO Auto-generated method stub


                // get Internet status
                isInternetPresent = cd.isConnectingToInternet();


                // check for Internet status
                if (isInternetPresent) {
                    // Internet Connection is Present
                    // make HTTP requests

                    Intent i = new Intent(getActivity(), GoogleActivity.class);
                    startActivity(i);       


                } else {
                    // Internet connection is not present
                    // Ask user to connect to Internet

                    showAlertDialog(Context ,  "No Internet Connection" ,  "You don't have internet connection.", true);

                }

                        }       });


            }
         public void showAlertDialog(Context HomeFragment, String title, String message, Boolean status) {
            AlertDialog alertDialog = new AlertDialog.Builder(HomeFragment).create();

            // Setting Dialog Title
            alertDialog.setTitle(title);

            // Setting Dialog Message
            alertDialog.setMessage(message);

            // Setting alert dialog icon
            alertDialog.setIcon((status) ? R.drawable.success : R.drawable.fail);

            // Setting OK Button
            alertDialog.setButton(DialogInterface.BUTTON_NEGATIVE,
                    "OK", new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialogInterface, int i) {

                        }
                    });

            // Showing Alert Message
            alertDialog.show();
        }   }

Logcat

01-06 16:22:48.940: W/dalvikvm(4223): threadid=1: thread exiting with uncaught exception (group=0x40de4540)
01-06 16:22:48.960: E/AndroidRuntime(4223): FATAL EXCEPTION: main
01-06 16:22:48.960: E/AndroidRuntime(4223): java.lang.NullPointerException
01-06 16:22:48.960: E/AndroidRuntime(4223):     at android.app.AlertDialog.resolveDialogTheme(AlertDialog.java:142)
01-06 16:22:48.960: E/AndroidRuntime(4223):     at android.app.AlertDialog$Builder.<init>(AlertDialog.java:359)
01-06 16:22:48.960: E/AndroidRuntime(4223):     at com.ons.bhoomi.HomeFragment.showAlertDialog(HomeFragment.java:90)
01-06 16:22:48.960: E/AndroidRuntime(4223):     at com.ons.bhoomi.HomeFragment$1.onClick(HomeFragment.java:77)
01-06 16:22:48.960: E/AndroidRuntime(4223):     at android.view.View.performClick(View.java:4102)
01-06 16:22:48.960: E/AndroidRuntime(4223):     at android.view.View$PerformClick.run(View.java:17085)
01-06 16:22:48.960: E/AndroidRuntime(4223):     at android.os.Handler.handleCallback(Handler.java:615)
01-06 16:22:48.960: E/AndroidRuntime(4223):     at android.os.Handler.dispatchMessage(Handler.java:92)
01-06 16:22:48.960: E/AndroidRuntime(4223):     at android.os.Looper.loop(Looper.java:155)
01-06 16:22:48.960: E/AndroidRuntime(4223):     at android.app.ActivityThread.main(ActivityThread.java:5520)
01-06 16:22:48.960: E/AndroidRuntime(4223):     at java.lang.reflect.Method.invokeNative(Native Method)
01-06 16:22:48.960: E/AndroidRuntime(4223):     at java.lang.reflect.Method.invoke(Method.java:511)
01-06 16:22:48.960: E/AndroidRuntime(4223):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1058)
01-06 16:22:48.960: E/AndroidRuntime(4223):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:825)
01-06 16:22:48.960: E/AndroidRuntime(4223):     at dalvik.system.NativeStart.main(Native Method)

Answer 1

Try this way,

public class HomeFragment extends Fragment {

    // flag for Internet connection status
    Boolean isInternetPresent = false;

    // Connection detector class
    ConnectionDetector cd;
    ImageButton button;

    public HomeFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        View rootView = inflater.inflate(R.layout.fragment_home, container, false);

        return rootView;
    }

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onActivityCreated(savedInstanceState);

        // creating connection detector class instance
        cd = new ConnectionDetector(getActivity());

        button = (ImageButton) getActivity().findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                isInternetPresent = cd.isConnectingToInternet();

                // check for Internet status
                if (isInternetPresent) {
                    // Internet Connection is Present
                    // make HTTP requests

                    Intent i = new Intent(getActivity(), GoogleActivity.class);
                    startActivity(i);

                } else {
                    // Internet connection is not present
                    // Ask user to connect to Internet

                    showAlertDialog(getActivity(), "No Internet Connection", "You don't have internet connection.", true);
                }
            }
        });
    }


    public void showAlertDialog(Context HomeFragment, String title, String message, Boolean status) {
        AlertDialog alertDialog = new AlertDialog.Builder(HomeFragment).create();

        // Setting Dialog Title
        alertDialog.setTitle(title);

        // Setting Dialog Message
        alertDialog.setMessage(message);

        // Setting alert dialog icon
        alertDialog.setIcon((status) ? R.drawable.success : R.drawable.fail);

        // Setting OK Button
        alertDialog.setButton(DialogInterface.BUTTON_NEGATIVE,
                "OK", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialogInterface, int i) {

                    }
                });

        // Showing Alert Message
        alertDialog.show();
    }
}

Answer 2

Your Context is null initialize it, add this peice of code in onActivityCreated

Context = getActivity().getApplicationContext();

Answer 3

Two changes

1. Change AlertDialog alertDialog to AlertDialog.Builder alertDialog

so it will be

AlertDialog.Builder alertDialog = new AlertDialog.Builder(HomeFragment); //Here i doubt instead of HomeFragment it should be getActivity()

2. Call alertDialog.create() ones you are done with dialog setup:-

   alertDialog.create().show();