Android: Twitpic upload error

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http://stackoverflow.com – In my android application i need to upload image to twitpic. But i get Runtime exception in my code. Here is my code... protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); uploadImage = (Button) findViewById(R.id.uploadImage); uploadImage.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { new ImageSender().execute(); } }); } private class ImageSender extends AsyncTask<URL, Integer, Long> { private String ur (HowTos)