问android中的登录界面出错

EN

public class MainActivity extends Activity{

    String username,password;

    HttpClient httpclient;
    HttpPost httppost;
    HttpResponse response;
    HttpEntity httpentity;
    ArrayList<NameValuePair> namevaluepairs;


    EditText etUser,etPass;
    Button bLogin;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        etUser=(EditText) findViewById(R.id.etUser);
        etPass=(EditText) findViewById(R.id.etPass);

        bLogin=(Button) findViewById(R.id.bSubmit);
        bLogin.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                httpclient=new DefaultHttpClient();
                httppost=new HttpPost("http://192.168.1.107/php_project/checking.php");

                username=etUser.getText().toString();
                password=etPass.getText().toString();

                try {

                    namevaluepairs=new ArrayList<NameValuePair>();

                    namevaluepairs.add(new BasicNameValuePair(username, username));
                    namevaluepairs.add(new BasicNameValuePair("password", password));

                    httppost.setEntity(new UrlEncodedFormEntity(namevaluepairs));
                    response=httpclient.execute(httppost);
                    if(response.getStatusLine().getStatusCode()==200){

                        httpentity=response.getEntity();

                        if(httpentity!=null){
                            InputStream inputstream=httpentity.getContent();

                            JSONObject jsonResponse=new JSONObject(convertStreamToString(inputstream));

                            String retUser=jsonResponse.getString("user");
                            String retPass=jsonResponse.getString("pass");

                            if(username.equals(retUser) && password.equals(retPass)){
                                SharedPreferences sp=getSharedPreferences("logindetails", 0);
                                SharedPreferences.Editor spedit=sp.edit();

                                spedit.putString("user", username);
                                spedit.putString("pass", password);

                                spedit.commit();

                                Toast.makeText(getApplicationContext(), "SUCCESS !", Toast.LENGTH_LONG).show();
                            }else{
                                Toast.makeText(getApplicationContext(), "Inavalid Login details", Toast.LENGTH_LONG).show();
                            }
                        }

                    }
                } catch (Exception e) {
                    e.printStackTrace();

                    Toast.makeText(getApplicationContext(), "Connection error", Toast.LENGTH_LONG).show();
                }                   
            }
        });


    }

    private static String convertStreamToString(InputStream is){

        BufferedReader reader=new BufferedReader(new InputStreamReader(is));
        StringBuilder sb=new StringBuilder();

        String line=null;

        try {
            while((line=reader.readLine())!=null){
                sb.append(line + "\n");
            }
        } catch (IOException e) {
            e.printStackTrace();
        }finally{
            try {
                is.close();
            } catch (IOException e2) {
                e2.printStackTrace();
            }
        }
        return sb.toString();


    }
}