Android Help with stopping activity crashing (FC) when no internet connection is present

I have followed a tutorial to download images remotely, it works fine when an internet connection is present, but when you launch the activity with no internet connection present the activity crashes "force Closes"

I'am unfortunately an android novice so i'm not sure what to do to stop it crashing. Is their a way to just toast a message stating "Sorry Internet is required" with a blank screen, nothing fancy, just to stop it crashing.

Hope someone can show me how to do this, Thankyou Lucy

private ImageAdapter imageAdapter;

private ArrayList<String> PhotoURLS = new ArrayList<String>();

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    this.requestWindowFeature(Window.FEATURE_NO_TITLE);
      this.getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN ,
            WindowManager.LayoutParams.FLAG_FULLSCREEN );

    setContentView(R.layout.galleryview);

    public static boolean isDataConnectionAvailable(Context context){
        ConnectivityManager connectivityManager = (ConnectivityManager)context.getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo info = connectivityManager.getActiveNetworkInfo();
        if(info == null)
            return false;

        return connectivityManager.getActiveNetworkInfo().isConnected();
    }

    imageAdapter = new ImageAdapter(this);
    final ImageView imgView = (ImageView) findViewById(R.id.GalleryView);
    Gallery g = (Gallery) findViewById(R.id.Gallery);
    g.setAdapter(imageAdapter);
    g.setOnItemClickListener(new OnItemClickListener() {
        public void onItemClick(AdapterView<?> parent, View v,
                int position, long id) {
            imgView.setImageDrawable(LoadImageFromURL(PhotoURLS
                    .get(position)));
            imgView.setScaleType(ImageView.ScaleType.FIT_XY);
        }
    });

    // replace this code to set your image urls in list
    PhotoURLS.add("http://domain.com/image-286.jpg"); 
    PhotoURLS.add("http://domain.com/image-285.jpg"); 
    PhotoURLS.add("http://domain.com/image-284.jpg"); 
    PhotoURLS.add("http://domain.com/image-283.jpg"); 
    PhotoURLS.add("http://domain.com/image-282.jpg"); 
    PhotoURLS.add("http://domain.com/image-281.jpg"); 


    new AddImageTask().execute();

}

class AddImageTask extends AsyncTask<Void, Void, Void> {
    @Override
    protected Void doInBackground(Void... unused) {
        for (String url : PhotoURLS) {
            String filename = url.substring(url.lastIndexOf("/") + 1,
                    url.length());
            filename = "th_" + filename;
            String thumburl = url.substring(0, url.lastIndexOf("/") + 1);
            imageAdapter.addItem(LoadThumbnailFromURL(thumburl + filename));
            publishProgress();
            //SystemClock.sleep(200);
        }

        return (null);
    }

    @Override
    protected void onProgressUpdate(Void... unused) {
        imageAdapter.notifyDataSetChanged();
    }

    @Override
    protected void onPostExecute(Void unused) {
    }
}

private Drawable LoadThumbnailFromURL(String url) {
    try {
        URLConnection connection = new URL(url).openConnection();
        String contentType = connection.getHeaderField("Content-Type");
        boolean isImage = contentType.startsWith("image/");
        if(isImage){
            HttpGet httpRequest = new HttpGet(url);
            HttpClient httpclient = new DefaultHttpClient();
            HttpResponse response = (HttpResponse) httpclient
                    .execute(httpRequest);
            HttpEntity entity = response.getEntity();
            BufferedHttpEntity bufferedHttpEntity = new BufferedHttpEntity(entity);

            InputStream is = bufferedHttpEntity.getContent();
            Drawable d = Drawable.createFromStream(is, "src Name");
            return d;
        } else {
            Bitmap b = BitmapFactory.decodeResource(getResources(), R.drawable.no_image);
            Drawable d = new BitmapDrawable(b);
            return d;
        }
    } catch (Exception e) {
        Toast.makeText(getApplicationContext(), "error", Toast.LENGTH_LONG)
                .show();
        Log.e(e.getClass().getName(), e.getMessage(), e);
        return null;
    }
}

private Drawable LoadImageFromURL(String url) {
    try {
        URLConnection connection = new URL(url).openConnection();
        String contentType = connection.getHeaderField("Content-Type");
        boolean isImage = contentType.startsWith("image/");
        if(isImage){
            HttpGet httpRequest = new HttpGet(url);
            HttpClient httpclient = new DefaultHttpClient();
            HttpResponse response = (HttpResponse) httpclient
                    .execute(httpRequest);
            HttpEntity entity = response.getEntity();
            BufferedHttpEntity bufferedHttpEntity = new BufferedHttpEntity(
                    entity);
            InputStream is = bufferedHttpEntity.getContent();

            // Decode image size
            BitmapFactory.Options o = new BitmapFactory.Options();
            o.inJustDecodeBounds = true;
            BitmapFactory.decodeStream(is, null, o);

            // The new size we want to scale to
            final int REQUIRED_SIZE = 320;

            // Find the correct scale value. It should be the power of 2.
            int width_tmp = o.outWidth, height_tmp = o.outHeight;
            int scale = 1;
            while (true) {
                if (width_tmp / 2 < REQUIRED_SIZE
                        || height_tmp / 2 < REQUIRED_SIZE)
                    break;
                width_tmp /= 2;
                height_tmp /= 2;
                scale *= 2;
            }

            // Decode with inSampleSize
            is = bufferedHttpEntity.getContent();
            BitmapFactory.Options o2 = new BitmapFactory.Options();
            o2.inSampleSize = scale;
            Bitmap b = BitmapFactory.decodeStream(is, null, o2);
            Drawable d = new BitmapDrawable(b);
            return d;
        } else {
            Bitmap b = BitmapFactory.decodeResource(getResources(), R.drawable.no_image);
            Drawable d = new BitmapDrawable(b);
            return d;
        }
    } catch (Exception e) {
        Toast.makeText(getApplicationContext(), "error", Toast.LENGTH_LONG)
                .show();
        Log.e(e.getClass().getName(), e.getMessage(), e);
        return null;
    }
}

public class ImageAdapter extends BaseAdapter {
    int mGalleryItemBackground;
    private Context mContext;

    ArrayList<Drawable> draw开发者_C百科ablesFromUrl = new ArrayList<Drawable>();

    public ImageAdapter(Context c) {
        mContext = c;
        TypedArray a = obtainStyledAttributes(R.styleable.GalleryTheme);
        mGalleryItemBackground = a.getResourceId(
        R.styleable.GalleryTheme_android_galleryItemBackground, 0);
        a.recycle();
    }

    public void addItem(Drawable item) {
        drawablesFromUrl.add(item);
    }

    public int getCount() {
        return drawablesFromUrl.size();
    }

    public Drawable getItem(int position) {
        return drawablesFromUrl.get(position);
    }

    public long getItemId(int position) {
        return position;
    }

    public View getView(int position, View convertView, ViewGroup parent) {
        ImageView i = new ImageView(mContext);

        i.setImageDrawable(drawablesFromUrl.get(position));
        i.setLayoutParams(new Gallery.LayoutParams(70, 110));
        i.setScaleType(ImageView.ScaleType.FIT_CENTER);
        //i.setBackgroundResource(mGalleryItemBackground);

        return i;


    }


}

}

you can check connection availability:

public static boolean isDataConnectionAvailable(Context context){
        ConnectivityManager connectivityManager = (ConnectivityManager)context.getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo info = connectivityManager.getActiveNetworkInfo();
        if(info == null)
            return false;

        return connectivityManager.getActiveNetworkInfo().isConnected();
    }

Note: Add permission to your manifest file:

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

I can confirm Vineet's answer is good as I had the same issue.

My code that was not working is as follows:

public boolean isOnline() {

final ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);        
final NetworkInfo networkInfo = cm.getActiveNetworkInfo();      
boolean connected = networkInfo.isConnected();

    if (connected)
        return true;
    else
        return false;

}

And the issue with my above example is that networkInfo.isConnected() does not appear to have a value. I was setting a boolean value to null, which (and yes my Java is sketchy since I am a newbie) I believe is not allowed, hence the app would throw up an exception and crash.

Here is now I solved it using Vineet’s solution.

public boolean isOnline() {

final ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);        
final NetworkInfo networkInfo = cm.getActiveNetworkInfo();      

if(networkInfo == null)
    return false;
else
    return networkInfo.isConnected();

}

Now, it works correctly and the app no longer crashes. Hope this solution helps someone. And I suspect a JAVA guru will be able to better explain the issue with setting boolean to Null not being allowed.