1

我尝试修复此错误，但我知道为什么某些nullpointer可以返回json成功。

public class Login extends Activity {
public TextView loginErrorMsg;
private ProgressDialog progressDialog;
private JSONObject jsonResult;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.bus_login);
            //findViewById
}

public void btnLogin_OnClick(View v) {

    new LoginTask().execute();
}

class LoginTask extends AsyncTask<String, String, JSONObject> {

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        progressDialog = new ProgressDialog(Login.this);
        progressDialog.setMessage("Logging in...");
        progressDialog.setIndeterminate(false);
        progressDialog.setCancelable(true);
        progressDialog.show();
    }


    protected JSONObject doInBackground(String... args) {
        // TODO Auto-generated method stub
        String uname = inputUserId.getText().toString();
        String password =inputPassword.getText().toString();
        UserFunctions vehicleFunction = new UserFunctions();
        jsonResult = vehicleFunction.loginVehicle(uname, password);

        return jsonResult;
    }

    protected void onPostExecute(JSONObject jsonResult) {
        // dismiss the dialog once done
        progressDialog.dismiss();

        try {

            int success = jsonResult.getInt("success");
            if (success == 1) {
                loginErrorMsg.setText("success");

            } else{
                loginErrorMsg.setText("Fail");
            }

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



    }

}

}

public JSONObject loginVehicle(String vehicleId, String password){
    List<NameValuePair> params = new ArrayList<NameValuePair>();
    params.add(new BasicNameValuePair("tag", login_tag));
    params.add(new BasicNameValuePair("vehicleId", vehicleId));
    params.add(new BasicNameValuePair("password", password));
    JSONObject json = jsonParser.getJSONFromUrl(loginVehicleURL, params);
    return json;
}


01-27 23:44:12.438: W/System.err(2121): java.lang.NullPointerException
01-27 23:44:12.438: W/System.err(2121):     at com.ptms.Bus_Login$LoginTask.onPostExecute(Bus_Login.java:79)
01-27 23:44:12.448: W/System.err(2121):     at com.ptms.Bus_Login$LoginTask.onPostExecute(Bus_Login.java:1)
01-27 23:44:12.448: W/System.err(2121):     at android.os.AsyncTask.finish(AsyncTask.java:602)
01-27 23:44:12.458: W/System.err(2121):     at android.os.AsyncTask.access$600(AsyncTask.java:156)
01-27 23:44:12.458: W/System.err(2121):     at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:615)
01-27 23:44:12.458: W/System.err(2121):     at android.os.Handler.dispatchMessage(Handler.java:99)
01-27 23:44:12.458: W/System.err(2121):     at android.os.Looper.loop(Looper.java:137)
01-27 23:44:12.458: W/System.err(2121):     at android.app.ActivityThread.main(ActivityThread.java:4424)
01-27 23:44:12.458: W/System.err(2121):     at java.lang.reflect.Method.invokeNative(Native Method)
01-27 23:44:12.458: W/System.err(2121):     at java.lang.reflect.Method.invoke(Method.java:511)
01-27 23:44:12.458: W/System.err(2121):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
01-27 23:44:12.458: W/System.err(2121):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
01-27 23:44:12.458: W/System.err(2121):     at dalvik.system.NativeStart.main(Native Method)
4

1 回答 1

1

请在 Eclipse 中调试您的应用程序。

签入此方法。我猜它在json中返回null。

public JSONObject loginVehicle(String vehicleId, String password){
    List<NameValuePair> params = new ArrayList<NameValuePair>();
    params.add(new BasicNameValuePair("tag", login_tag));
    params.add(new BasicNameValuePair("vehicleId", vehicleId));
    params.add(new BasicNameValuePair("password", password));
    JSONObject json = jsonParser.getJSONFromUrl(loginVehicleURL, params);
    return json;
}

签入此行 

JSONObject json = jsonParser.getJSONFromUrl(loginVehicleURL, params);

并且您正在访问包含 null 的 jsonResult。

int success = jsonResult.getInt("success");
于 2013-01-27T16:14:47.377 回答