Android Firebase Clould Function:Take Control Of Your Firebase Backend
Introduction
Firebase introduces cloud functions to write server side code in firebase. With firebase Cloud Functions, all you need to do to have the server side functionality is to write functions and deploy them.
Now as an Android Developer at first you might find it a little mess because you can’t write cloud functions in firebase in nativtive languages like kotlin or java.Instead you have to use either one of the two 1.Javascript 2.Typescript
In this post, i will show you how you can setup Firebase cloud functions project, cloud functions triggers, writing cloud functions, using node.js modules, deploying cloud functions and using cloud functions in android.
Setting Up Cloud Functions Project
To manage and deploy Firebase cloud functions project, Firebase command line interface needs to be installed on development machine. Below are the steps to complete the required setup.
To install Firebase CLI, NodeJS and npm needs to be installed. To install both Node.js and npm, go to Node Js website and download Node.js windows installer package and follow these steps
1.run it to get setup wizard and click next.
2.Accept license by checking the check box and click next.
3.Choose destination folder and click next.
4.Select the way features are installed, if you don’t need documentation short cuts select the option from the drop down and then click next.
5.Then click install to complete node.js and npm installation.
Then install Firebase command line by opening command prompt and running below command.
npm install -g firebase-tools
Then login to Firebase from firebase command line by entering firebase login command in command prompt. It will open browser, enter your firebase account credentials and login.
Oncethis login is successful, create cloud functions project by going to the directory where you want to create the project and entering below command.
firebase init functions
It will prompt you to select existing Firebase project or create new project. Once project is selected, it will ask you to select language for writing cloud functions. It provides JavaScript and TypeScript options. Once language option is chosen, it will ask you if you want to install dependencies with npm.Finally it creates cloud functions project.
The structure of firebase cloud functions project consists oftThe main source file which is index.js.And there is another file called packages,json where you have write all of your dependencies.
With that, Firebase cloud functions project setup is complete and now you can start writing cloud functions.
Cloud Function Triggers
Before we start writing cloud functions, we need to know about the triggers which run the functions. Cloud functions are run in response to http requests, Firebase Firestore events, cloud pub/sub events, cloud storage events, analytics events, crashlytics events, realtime database events and authentication events.
When you write functions, you need to use the object exported by Cloud Functions for Firebase SDK that listens to the event provider that you are targeting. For example, to run your cloud function in response to http requests, you need to use functions.https provided by The Cloud Functions for Firebase SDK.
You can check this video series of firebase to get more details here
And here goes some sample cloud function github source codes
Writing Cloud Functions
You can write your Firebase cloud functions in index.js file which is the main node.js source file. You can create java script functions in separate files and import and use them in index.js. There are several useful Node.js modules which make creating cloud functions easy. For example validator module for validating strings, moment module for handling dates and express modules provide web framework for developing websites, etc.
Let’s see an example of a cloud function. The example cloud function will be triggered in response to http requests and it validates the credit card number sent in http request. It can handle both Http Get and Post requests. The function uses validator module. Add this function to index.js and deploy it as described in the following section.
const moment = require(‘validator’);
exports.isCreditCard = functions.https.onRequest((req, res) => {
if (req.method === ‘PUT’) {
res.status(403).send(‘Forbidden!’);
}
cors(req, res, () => {
let ccnum = req.query.ccnum;
if (!ccnum) {
ccnum = req.body.ccnum;
}
let msg;
if(validator().isCreditCard(ccnum)){
msg = ‘Valid credit card’;
}else{
msg = ‘Invalid credit card’;
}
res.status(200).send(msg);
});
});Deploying Cloud Functions
You can deploy cloud functions to Firebase server using firebase deploy command.
firebase deploy
To deploy only specific functions, you can use below command specifying function name to be deployed. You can test your functions by using URL for each function that prints after the deployment.
firebase deploy — only functions:validateString
To fix it, you need to install missing node.js modules by using bellow command from functions directory.
npm install
To install specific node.js module, you need to use g option, for example to install express cors module below is the command.
npm install -g cors
So it is important that the node.js modules which you use in your cloud functions are added to package.json file. Below is an example package.json file with dependencies.
{
“name”: “functions”,
“description”: “Cloud Functions for Firebase”,
“scripts”: {
“serve”: “firebase serve — only functions”,
“shell”: “firebase experimental:functions:shell”,
“start”: “npm run shell”,
“deploy”: “firebase deploy — only functions”,
“logs”: “firebase functions:log”
},
“dependencies”: {
“cors”: “².8.4”,
“firebase-admin”: “~5.4.2”,
“firebase-functions”: “⁰.7.1”,
“validator”: “⁹.2.0”
},
“private”: true
}Monitoring Cloud Functions
To view deployed cloud functions, login to Firebase console , click functions in the left navigation and view cloud functions dashboard.
Firebase Cloud Functions Android Example
Below android example shows how to use of firebase cloud function in android. The example lets users enter the order amount to know the discount information. App sends https request to Firebase function using
OkHttp. Firebase function calculates discount using the order amount sent in http request and returns the discount information to app.
Firebase Cloud Function Http
For the android example, firebase cloud function that is trigged by http request is defined and deployed to firebase.
const functions = require(‘firebase-functions’);
const cors = require(‘cors’)({origin: true});
const validator = require(‘validator’);
exports.discount = functions.https.onRequest((req, res) => {
if (req.method === ‘PUT’) {
res.status(403).send(‘Forbidden!’);
}
cors(req, res, () => {
let amount = req.query.orderAmt;
if (!amount) {
amount = req.body.orderAmt;
}
let discount;
if(validator.isNumeric(amount)){
discount = ‘Invalid Order Amount’;
}else{
if (amount < 200){
discount = ‘Eligible for extra 10% off’;
}else if(amount > 199 && amount < 400){
discount = ‘Eligible for extra 15% off’;
}else if(amount > 399 && amount < 600){
discount = ‘Eligible for extra 20% off’;
}else{
discount = ‘Eligible for extra 25% off’;
}
}
res.status(200).send(discount);
});
});Activity
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;import java.io.IOException;import okhttp3.Call;
import okhttp3.Callback;
import okhttp3.HttpUrl;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;
import okhttp3.ResponseBody;
import zoftino.com.firestore.R;public class OrderDiscountActivity extends AppCompatActivity {private static final String TAG = “OrderDiscountActivity”;private String FIREBASE_CLOUD_FUNCTION_URL
= “https://us-central1-yourfirebaseproject.cloudfunctions.net/discount";
private EditText orderaAmt;@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.order_dicount_layout);Toolbar tb = findViewById(R.id.toolbar);
setSupportActionBar(tb);orderaAmt = findViewById(R.id.order_amt);
Button discountButton = findViewById(R.id.order_amt_b);
discountButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
findDiscountAmt();
}
});
}public void findDiscountAmt() {
String orderAmt = orderaAmt.getText().toString();
double orderAmount;
try {
orderAmount = Double.parseDouble(orderAmt);
}catch (Exception e){
orderaAmt.setError(“Enter valid amount”);
return;
}
sendMessageToFcm(orderAmount);
}private void sendMessageToFcm(double orderAmount) {OkHttpClient httpClient = new OkHttpClient();HttpUrl.Builder httpBuider =
HttpUrl.parse(FIREBASE_CLOUD_FUNCTION_URL).newBuilder();
httpBuider.addQueryParameter(“orderAmt”, “”+orderAmount);Request request = new Request.Builder().
url(httpBuider.build()).build();httpClient.newCall(request).enqueue(new Callback() {
@Override public void onFailure(Call call, IOException e) {
Log.e(TAG, “error in getting response from firebase cloud function”);runOnUiThread(new Runnable() {
@Override
public void run() {
Toast.makeText(OrderDiscountActivity.this,
“Cound’t get response from cloud function”,
Toast.LENGTH_SHORT).show();
}
});
}
@Override public void onResponse(Call call, Response response){
ResponseBody responseBody = response.body();
String resp = “”;
if (!response.isSuccessful()) {
Log.e(TAG, “fail response from firebase cloud function”);
Toast.makeText(OrderDiscountActivity.this,
“Cound’t get response from cloud function”,
Toast.LENGTH_SHORT).show();
}else {
try {
resp = responseBody.string();
} catch (IOException e) {
resp = “Problem in getting discount info”;
Log.e(TAG, “Problem in reading response “ + e);
}
}
runOnUiThread(responseRunnable(resp));
}
});
}
private Runnable responseRunnable(final String responseStr){
Runnable resRunnable = new Runnable(){
public void run(){
Toast.makeText(OrderDiscountActivity.this
,responseStr,
Toast.LENGTH_SHORT).show();
}
};
return resRunnable;
}
}
Activity Layout
<?xml version=”1.0" encoding=”utf-8"?>
<LinearLayout
xmlns:android=”http://schemas.android.com/apk/res/android"
xmlns:tools=”http://schemas.android.com/tools"
android:layout_width=”match_parent”
android:layout_height=”match_parent”
android:orientation=”vertical”
android:gravity=”center_horizontal”
tools:context=”zoftino.com.firebase.cloudfuncion.OrderDiscountActivity”>
<android.support.v7.widget.Toolbar
android:id=”@+id/toolbar”
android:layout_width=”match_parent”
android:layout_height=”?attr/actionBarSize”
android:background=”?attr/colorPrimary” />
<TextView
android:layout_width=”wrap_content”
android:layout_height=”wrap_content”
android:layout_marginLeft=”4dp”
android:layout_marginRight=”4dp”
android:textAppearance=”@style/TextAppearance.AppCompat.Headline”
android:text=”Enter Order Amt & Find Discount”
android:layout_marginTop=”16dp”/>
<android.support.design.widget.TextInputLayout
android:id=”@+id/order_amt_l”
android:layout_width=”match_parent”
android:layout_height=”wrap_content”
android:layout_marginLeft=”4dp”
android:layout_marginRight=”4dp”>
<android.support.design.widget.TextInputEditText
android:id=”@+id/order_amt”
android:layout_width=”match_parent”
android:layout_height=”wrap_content”
android:inputType= “numberDecimal”
android:hint=”Enter Order Amount”/>
</android.support.design.widget.TextInputLayout>
<Button
android:id=”@+id/order_amt_b”
android:layout_width=”wrap_content”
android:layout_height=”wrap_content”
style=”@style/Widget.AppCompat.Button.Colored”
android:text=”Know Discount Amount”/>
</LinearLayout>And that’s it.To explore more check out github firebase samples of cloud function!
