i have tried this code many times. But it always force closes. Can anyone find out the error in the code

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http://stackoverflow.com – this code is for getting details from a php server by posting two data num,db and getting a response. public class MainActivity extends Activity { Button b; TextView num; TextView dob; String db; String x; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); b=(Button) findViewById(R.id.button1); num=(TextView) findViewById(R.id.editText1); dob=(TextView) findViewById(R.id.editText2); x=(String) num.getText(); db=(String) dob.getText(); b.setOnClickListener(new View.OnCl (HowTos)