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.