Login Example in Android using POST method using REST API

Question

I am working on my First Android application where we have our own REST API, url will be like. "www.abc.com/abc/def/" . For login activity i need to do httppost by passing 3 parameters as identifier, email and password. Then after getting the http response, i need to show the dialogbox whether Invalid Credentials or Switch to another activity.

Can someone please show me sample code for how to do this?

Answer 1

An easy way to complete this task is to using a library, if your familiar with libraries. I recommend Ion because it's small and easy to work with. Add the library and add the following snippet to the method of your choice.

Ion.with(getApplicationContext())
.load("http://www.example.com/abc/def/")
.setBodyParameter("identifier", "foo")
.setBodyParameter("email", "[email protected]")
.setBodyParameter("password", "p@ssw0rd")
.asString()
.setCallback(new FutureCallback<String>() {
   @Override
    public void onCompleted(Exception e, String result) {
        // Result
    }
});

Notice! If you want to make network calls you must add the following permission to your AndroidManifest.xml outside the <application> tag if you're not aware of that.

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

To check the response for successful login, or failure you can add the following snippet inside the onComplete-method (where the // Result is).:

    try {
        JSONObject json = new JSONObject(result);    // Converts the string "result" to a JSONObject
        String json_result = json.getString("result"); // Get the string "result" inside the Json-object
        if (json_result.equalsIgnoreCase("ok")){ // Checks if the "result"-string is equals to "ok"
            // Result is "OK"
            int customer_id = json.getInt("customer_id"); // Get the int customer_id
            String customer_email = json.getString("customer_email"); // I don't need to explain this one, right?
        } else {
            // Result is NOT "OK"
            String error = json.getString("error");
            Toast.makeText(getApplicationContext(), error, Toast.LENGTH_LONG).show(); // This will show the user what went wrong with a toast
            Intent to_main = new Intent(getApplicationContext(), MainActivity.class); // New intent to MainActivity
            startActivity(to_main); // Starts MainActivity
            finish(); // Add this to prevent the user to go back to this activity when pressing the back button after we've opened MainActivity
        }
    } catch (JSONException e){
        // This method will run if something goes wrong with the json, like a typo to the json-key or a broken JSON.
        Log.e(TAG, e.getMessage());
        Toast.makeText(getApplicationContext(), "Please check your internet connection.", Toast.LENGTH_LONG).show();
    }

Why do we need a try & catch, well first of all we are forced to and on the other hand, it will prevent the application to crash if something goes wrong with the JSON-parsing.

Answer 2

this is how you can handle this from scratch, in your login Activity use this block of code and if you are using POST method you will modify a little bit because I used a GET Method to check credidentials, LoginHandler extends AsyncTask because it is not allowed to make Network Operations on main Thread...

private class  LoginHandler extends AsyncTask<String, Void, Boolean> {

        @Override
        protected Boolean doInBackground(String... params) {
            // TODO Auto-generated method stub

            String URL = "url to get from ";

            JSONObject jsonReader=null;


            try {

                // TODO Auto-generated method stub
                HttpClient httpclient = new DefaultHttpClient();
                HttpResponse response;
                String responseString = null;
                try {
                    response = httpclient.execute(new HttpGet(URL));
                    StatusLine statusLine = response.getStatusLine();
                    if (statusLine.getStatusCode() == HttpStatus.SC_OK) {
                        ByteArrayOutputStream out = new ByteArrayOutputStream();
                        response.getEntity().writeTo(out);
                        out.close();
                        responseString = out.toString();
                        jsonReader=new JSONObject(responseString);
                    } else {
                        // Closes the connection.
                        response.getEntity().getContent().close();
                        throw new IOException(statusLine.getReasonPhrase());
                    }
                } catch (ClientProtocolException e) {
                    // TODO Handle problems..
                    String er=e.getMessage();
                } catch (IOException e) {
                    // TODO Handle problems..
                    String er=e.getMessage();
                }

                // Show response on activity

                if (!jsonReader.get("UserName").toString().equals("")) {
                    SharedPreferences sp = getSharedPreferences("LoginInfos", 0);
                    Editor editor = sp.edit();

                    editor.putString("email", jsonReader.getString("EmailAddress"));
                    editor.putString("username", jsonReader.getString("UserName"));
                    editor.putString("userid", jsonReader.getString("UserId"));
                    editor.putString("realname", jsonReader.getString("RealName"));
                    editor.putString("realsurname", jsonReader.getString("RealSurname"));
                    editor.putString("userprofileimage", jsonReader.getString("UserProfileImage"));




                    DateFormat dateFormat = new SimpleDateFormat(
                            "yyyy.MM.dd HH:mm:ss");
                    // get current date time with Date()
                    Date date = new Date();

                    editor.putString("LastLogin",
                            dateFormat.format(date.getTime()));
                    editor.commit();
                    return true;
                }
                return false;

            } catch (Exception ex) {

            }

            return false;
        }

        // TODO Auto-generated method stub

        @Override
        protected void onPostExecute(Boolean result) {
            // TODO Auto-generated method stub


            if (result) {
                pdialog.dismiss();
                Intent userMainActivityIntent = new Intent(
                         getApplicationContext(), MainUserActivity.class);
                startActivity(userMainActivityIntent);
            }
            else
            {
                pdialog.dismiss();
                new AlertDialog.Builder(MainActivity.this).setTitle("Login Error")
                .setMessage("Email or password is wrong.").setCancelable(false)
            .setPositiveButton("OK",new DialogInterface.OnClickListener() {

                @Override
                public void onClick(DialogInterface dialog, int which) {
                    // TODO Auto-generated method stub
                    dialog.cancel();
                }
            } ).show();

            }




            super.onPostExecute(result);


        }

    }