Mobile Programming - Android

1. Google Firebase
TK2323 Mobile Programming
Sem 1 2017/2018
Lam Meng Chun
lammc@ukm.edu.my (G-02)

2. Firebase2

3. Firebase Realtime
Database
Store and sync data in real time across all connected clients
3

4. Firebase Realtime Database
▹ The Firebase Realtime Database is a cloud-hosted
database.
▹ Data is stored as JSON and synchronized in realtime
to every connected client.
▹ When you build cross-platform apps with our iOS,
Android, and JavaScript SDKs, all of your clients
share one Realtime Database instance and
automatically receive updates with the newest
data.
4

5. Firebase Realtime Database-
KEY CAPABILITIES
Realtime
Instead of typical HTTP requests, the
Firebase Realtime Database uses data
synchronization—every time data
changes, any connected device
receives that update within
milliseconds. Provide collaborative
and immersive experiences without
thinking about networking code.
Offline
Firebase apps remain responsive even
when offline because the Firebase
Realtime Database SDK persists your
data to disk. Once connectivity is
reestablished, the client device
receives any changes it missed,
synchronizing it with the current
server state.
5

6. Firebase Realtime Database-
KEY CAPABILITIES
Accessible from Client Devices
The Firebase Realtime Database can be accessed directly from a mobile
device or web browser; there’s no need for an application server. Security and
data validation are available through the Firebase Realtime Database Security
Rules, expression-based rules that are executed when data is read or written.
6

7. Example
7

8. Firebase
Authentication
Authenticate and manage users from a variety of providers without server-side
code
8

9. Firebase Authentication
▹ Firebase Authentication provides backend services,
easy-to-use SDKs, and ready-made UI libraries to
authenticate users to your app.
▹ It supports authentication using passwords,
popular federated identity providers like Google,
Facebook and Twitter, and more.
9

10. Firebase Authentication -
KEY CAPABILITIES
FirebaseUI (beta)
The FirebaseUI Auth component
implements best practices for
authentication on mobile devices and
websites, which can maximize sign-in
and sign-up conversion for your app.
It also handles edge cases like
account recovery and account linking
that can be security sensitive and
error-prone to handle correctly
Email and password based
authentication
Authenticate users with their email
addresses and passwords. The
Firebase Authentication SDK provides
methods to create and manage users
that use their email addresses and
passwords to sign in. Firebase
Authentication also handles sending
password reset emails.
10

11. Firebase Authentication -
KEY CAPABILITIES
Federated identity provider
integration
Authenticate users by integrating with
federated identity providers. The
Firebase Authentication SDK provides
methods that allow users to sign in
with their Google, Facebook, Twitter,
and GitHub accounts.
Custom auth system integration
Connect your app's existing sign-in
system to the Firebase Authentication
SDK and gain access to Firebase
Realtime Database and other Firebase
services.
11

12. Firebase Authentication -
KEY CAPABILITIES
Anonymous auth
Use Firebase features that require
authentication without requiring
users to sign in first by creating
temporary anonymous accounts. If
the user later chooses to sign up, you
can upgrade the anonymous account
to a regular account, so the user can
continue where they left off.
12

13. Example
13

14. Firebase Cloud
Messaging
Firebase Cloud Messaging (FCM) is a cross-platform messaging solution that lets
you reliably deliver messages at no cost.
14

15. Firebase Cloud Messaging
▹ Using FCM, you can notify a client app that new
email or other data is available to sync. You can
send notification messages to drive user
reengagement and retention.
▹ For use cases such as instant messaging, a message
can transfer a payload of up to 4KB to a client app.
15

16. Firebase Cloud Messaging -
KEY CAPABILITIES
Send notification messages or data
messages
Send notification messages that are
displayed to your user. Or send data
messages and determine completely
what happens in your application
code.
Versatile message targeting
Distribute messages to your client app
in any of three ways — to single
devices, to groups of devices, or to
devices subscribed to topics.
16

17. Firebase Cloud Messaging -
KEY CAPABILITIES
Send messages from client apps
Send acknowledgments, chats, and
other messages from devices back to
your server over FCM’s reliable and
battery-efficient connection channel..
17

18. Firebase
Notifications
Firebase Notifications is a free service that enables targeted user notifications for
mobile app developers.
18

19. Firebase Notifications
▹ Built on Firebase Cloud Messaging and the FCM
SDK, Firebase Notifications (Notifications) provides
an option for developers and organizations seeking
a flexible notification platform that requires
minimal coding effort to get started, and a
graphical console for sending messages.
▹ Using the Notifications console GUI, you can
reengage and retain your userbase, foster app
growth, and support marketing campaigns.
19

20. Firebase Notifications- KEY
CAPABILITIES
Notifications analytics
Analyze reengagement conversion
with built-in notifications analytics
collection and funnel analysis.
Versatile message targeting
Target clients in predefined user
segments, custom analytics
audiences, clients subscribed to
topics, and single devices.
20

21. Firebase Notifications- KEY
CAPABILITIES
Flexible message scheduling
Deliver notifications (up to 2kb)
immediately, or at a future time in the
client's local time
21

22. Firebase Storage
Store and retrieve user-generated content such as images, audio and video without
server-side code
22

23. Firebase Storage
▹ Firebase Storage adds Google security to file
uploads and downloads for your Firebase apps,
regardless of network quality.
▹ You can use it to store images, audio, video, or
other user-generated content.
▹ Firebase Storage is backed by Google Cloud
Storage, a powerful, simple, and cost-effective
object storage service.
23

24. Firebase Storage - KEY
CAPABILITIES
Robust operations
Firebase Storage
performs uploads and
downloads regardless
of network quality.
Uploads and downloads
are robust, meaning
they restart where they
stopped, saving your
users time and
bandwidth.
Strong security
Firebase Storage
integrates with Firebase
Authentication to
provide simple and
intuitive authentication
for developers. You can
use our declarative
security model to allow
access based on
filename, size, content
type, and other
High scalability
Firebase Storage is
backed by Google Cloud
Storage for petabyte
scale when your app
goes viral. Effortlessly
grow from prototype to
production using the
same infrastructure that
powers Snapchat.
24

25. Firebase Hosting
Deploy web and mobile web apps in seconds using a secure global content delivery
network
25

26. Firebase Hosting
▹ Firebase Hosting is production-grade web content
hosting for developers.
▹ With Hosting, you can quickly and easily deploy
web apps and static content to a global content-
delivery network (CDN) with a single command.
26

27. KEY CAPABILITIES
Served over a secure connection
The modern web is secure. Zero-
configuration SSL is built into
Firebase Hosting so content is
always delivered securely.
Fast content delivery
Each file you upload is cached on
SSDs at CDN edges around the world.
No matter where your users are, the
content is delivered fast.
27

28. KEY CAPABILITIES
Rapid deployment
Using the Firebase CLI, you can get
your app up and running in seconds.
Command line tools make it easy to
add deployment targets into your
build process.
One-click rollbacks
Quick deployments are great, but
being able to undo mistakes is even
better. Firebase Hosting provides full
versioning and release management
with one-click rollbacks.
28

29. Firebase Test Lab
for Android
Test your Android apps against a wide range of physical devices
29

30. Firebase Test Lab
▹ Firebase Test Lab for Android provides cloud-based
infrastructure for testing Android apps.
▹ With one operation, you can initiate testing of your
app across a wide variety of devices and device
configurations.
30

31. Firebase Test Lab
▹ Test results—including logs, videos, and
screenshots—are made available in your project in
the Firebase console.
▹ Even if you haven't written any test code for your
app, Test Lab can exercise your app automatically,
looking for crashes.
31

32. Firebase Test Lab - KEY
CAPABILITIES
Test on real devices
Use Test Lab to exercise your app on
devices installed and running in a
Google data center. Test Lab helps
you to find issues that only occur on
specific device configurations (for
example, a Nexus 5 running a specific
Android API level and specific locale
settings).
Run app tests, even if you haven't
written any
You can use Robo test to find issues
with your app so you can test your
app even if you haven't written app
tests. Robo test analyzes the
structure of your app's user interface
and then explores it, automatically
simulating user activities. If you have
written instrumentation tests for
your app, Test Lab can also run those
tests.
32

33. Firebase Test Lab - KEY
CAPABILITIES
Workflow integration
Test Lab is integrated with Android
Studio, the Firebase console, and the
gcloud command line. You can also
use Test Lab with Continuous
Integration (CI) systems.
33

34. Firebase Crash
Reporting
Get actionable insights and comprehensive analytics whenever your app crashes or
stops working.
34

35. Firebase Crash Reporting
▹Crash Reporting creates detailed reports of the
errors in your app.
▹Errors are grouped into clusters of similar stack
traces and triaged by the severity of impact on your
users.
▹In addition to automatic reports, you can log custom
events to help capture the steps leading up to a crash.
35

36. Firebase Crash Reporting-
KEY CAPABILITIES
Monitor fatal and non-fatal errors
Monitor fatal errors in iOS and fatal
and non-fatal errors in Android.
Reports are triaged by the severity of
impact on users.
Collect the data you need to
diagnose problems
Each report contains a full stack
trace as well as device
characteristics, performance data,
and user circumstances when the
error took place. Similar reports are
automatically clustered to make it
easier to identify related bugs.
36

37. Firebase Crash Reporting-
KEY CAPABILITIES
Integrate with Analytics
Errors captured are set as
app_exception events in Analytics,
allowing you to filter audiences
based on who sees errors.
Free and easy
Crash Reporting is free to use. Once
you've added Firebase to your app,
it's just a few lines of code to enable
comprehensive error reporting.
37

38. Example
38

39. Firebase Analytics
Get detailed analytics to measure and analyse how users engage with your app
39

40. FIREBASE ANALYTICS
▹a free and unlimited analytics tool built from the ground up
for mobile apps.
▹Firebase Analytics is at the core of the Firebase platform,
providing the insights you need to build successful apps.
▹Firebase Analytics helps you understand how your users
behave, so you can make informed decisions about how to
market your app.
40

41. FIREBASE ANALYTICS -
METRICS
▹average revenue per user
(ARPU),
▹active users,
▹retention reports,
▹event counts
▹combined with user properties
like device type, app version, and
OS version to give you insight into
how users interact with your app.
41

42. KEY CAPABILITIES
BigQuery
Link your Firebase Analytics app to
BigQuery where you can perform
custom analysis on your entire
Analytics dataset and import other
data sources.
Firebase Crash Reporting
Firebase Analytics logs events for
each crash so you can get a sense of
the rate of crashes for different
versions or regions, allowing you to
gain insight into which users are
impacted. You can also create
audiences for users who have
experienced multiple crashes and
respond with Firebase Notifications
directed at that audience.
42

43. KEY CAPABILITIES
Firebase Remote
Config
Use Firebase Analytics
audience definitions to
change the behavior
and appearance of your
app for different
audiences without
distributing multiple
versions of your app.
Google Tag Manager
Integrating Google Tag
Manager alongside
Firebase Analytics
enables you to manage
your Firebase Analytics
implementation
remotely from a web
interface after your app
has been distributed.
Firebase Notifications
Firebase Analytics
automatically logs
events that correspond
to your Firebase
Notifications and
supports reporting on
the impact of each
campaign.
43

44. Firebase Remote
Config
Customise and experiment with app behaviour using server-side configuration
parameters
44

45. Firebase Remote Config
▹Firebase Remote Config is a cloud service that lets you
change the behavior and appearance of your app without
requiring users to download an app update.
▹When using Remote Config, you create in-app default values
that control the behavior and appearance of your app.
▹Then, you can later use the Firebase console to override in-
app default values for all app users or for segments of your
userbase.
▹Your app controls when updates are applied, and it can
frequently check for updates and apply them with a negligible
impact on performance.
45

46. Firebase Remote Config -
KEY CAPABILITIES
Quickly roll out changes to your
app's userbase
You can make changes to your app's
default behavior and appearance by
changing server-side parameter
values. For example, you could
change your app's layout or color
theme to support a seasonal
promotion, with no need to publish
an app update.
Customize your app for segments
of your userbase
You can use Remote Config to
provide variations on your app's user
experience to different segments of
your userbase by app version, by
Firebase Analytics audience, by
language, and more.
46

47. Firebase Remote Config -
KEY CAPABILITIES
Run A/B tests to improve your app
You can use Remote Config random
percentile targeting with Firebase
Analytics to A/B test improvements
to your app across different
segments of your userbase so that
you can validate improvements
before rolling them out to your entire
userbase.
47

48. Example
48

49. Firebase App
Indexing
Firebase App Indexing gets your app into Google Search
49

50. Firebase Remote Config
▹Firebase App Indexing gets your app into Google Search. If
your Android app is already installed when users search for
related content, they will launch your app directly from Search
results.
▹If users don’t have your app yet, an install card shows up in
Search results for Android.
▹Adding App Indexing promotes both types of app results
within Google Search and also provides query autocompletions.
50

51. Example
51

52. AdMob
Earn more from your apps the smart way by showing ads from millions of Google
advertisers
52

53. AdMob
▹AdMob by Google is a mobile advertising platform that you
can use to generate revenue from your app.
▹Using AdMob with Firebase Analytics provides you with
additional app usage data and analytics capabilities.
▹Firebase integrates with AdMob without requiring changes to
your existing AdMob configuration.
53

54. AdMob - KEY CAPABILITIES
Earn more from AdMob's in-app
ads
Show ads from millions of Google
advertisers in real time, or use
AdMob Mediation to earn from over
40 premium networks through the
AdMob platform to simplify your ad
operations, improve competition,
and earn more, for free.
Improve user experience
Native and video ads create a
positive user experience as you
monetize by matching the look and
feel of your app. Choose from
different ad templates, customize
them, and experiment with different
layouts on the fly without
republishing your app.
54

55. AdMob - KEY CAPABILITIES
Scale fast
▹When your app's a global or
domestic hit, you can monetize users
quickly with AdMob, by showing ads
to users in more than 200 markets.
▹More than one app? AdMob house
ads is a free tool that enables you to
cross-promote your apps to your
userbase, across your family of apps.
Access monetization reports
AdMob is the premier monetization
platform for mobile. While
generating ad revenue, AdMob also
produces its own monetization
reports that you can use to make
smarter decisions about product
strategy.
55

56. Example
56

57. 57
Take a Break

58. Firebase Setup
https://firebase.google.com/docs/android/setup
58

59. 59
59

60. 60
60

61. Firebase
Authentication
Authenticate and manage users from a variety of providers without server-side
code
61

62. Firebase – Instantiate62
private FirebaseAuth mFirebaseAuth;
private FirebaseUser mFirebaseUser;
private DatabaseReference mDatabase;
// Initialize Firebase Auth and Database Reference
mFirebaseAuth = FirebaseAuth.getInstance();
mFirebaseUser = mFirebaseAuth.getCurrentUser();
mUserId = mFirebaseUser.getUid();
mDatabase = FirebaseDatabase.getInstance().getReference();

63. Firebase Authentication63
// initialize the FirebaseAuth instance
mFirebaseAuth = FirebaseAuth.getInstance();
//If a user has signed in successfully you can get their account data at any point
with the getCurrentUser method.
//get a FirebaseUser object, which contains information about the signed-in user.
mFirebaseUser = mFirebaseAuth.getCurrentUser();
if (mFirebaseUser == null) {
// Not logged in, launch the Log In activity
loadLogInView();
} else {
// User is signed in
mUserId = mFirebaseUser.getUid();
}

64. Firebase Authentication -
signup64
mFirebaseAuth.createUserWithEmailAndPassword(email, password)
.addOnCompleteListener(SignUpActivity.this, new OnCompleteListener<AuthResult>() {
@Override
public void onComplete(@NonNull Task<AuthResult> task) {
if (task.isSuccessful()) {
Intent intent = new Intent(SignUpActivity.this, MainActivity.class);
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK);
startActivity(intent);
} else {
AlertDialog.Builder builder = new AlertDialog.Builder(SignUpActivity.this);
builder.setMessage(task.getException().getMessage())
.setTitle(R.string.login_error_title)
.setPositiveButton(android.R.string.ok, null);
AlertDialog dialog = builder.create();
dialog.show();
}
}
});

65. Firebase Authentication -
signin65
mFirebaseAuth.signInWithEmailAndPassword(email,password).addOnCompleteListener(LogInActivity.this, new
OnCompleteListener<AuthResult>() {
@Override
public void onComplete(@NonNull Task<AuthResult> task) {
if(task.isSuccessful())
{
GoToMainAvtivity();
} else
{
Toast.makeText(LogInActivity.this,"Error",Toast.LENGTH_SHORT).show();
}
}
});

66. Firebase Authentication -
SignOut66
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
if (id == R.id.action_logout) {
mFirebaseAuth.signOut();
Intent intent = new Intent(MainActivity.this, LogInActivity.class);
startActivity(intent);
}
return super.onOptionsItemSelected(item);
}

67. Firebase Authentication –
Check User Status67
if (mFirebaseUser == null) {
// go to loginpage
Intent intent = new Intent(MainActivity.this, LogInActivity.class);
startActivity(intent);
}

68. Firebase Authentication68

69. Firebase – Rules69

70. JSON
70

71. 71 JSON
▹JSON (JavaScript Object Notation) is a lightweight data-
interchange format.
▸Data is in name/value pairs
▸Data is separated by commas ,
▸Curly braces hold objects { }
▸Square brackets hold arrays [ ]
71

72. 72 Name/Value pairs
Name Value:
{ “Matrix No” : “A111111” }

73. 73 JSON
▹JSON values can be:
▸A number (integer or floating point)
▸A string (in double quotes) “”
▸A Boolean (true or false)
▸An array (in square brackets) []
▸An object (in curly braces) {}
▸null
73

74. 74 Name/Value pairs
Name Value:
{ “Matrix No” : “A111111” }
{ “Fees” : 500.00}
String Matrix No = “A111111”;
float Fees = 500.00;

75. 75 JSON
▹A number (integer or
floating point)
▹A string (in double
quotes)
▹A Boolean (true or
false)
75
{
“Burger Price“ : 20.0
}
{
“Burger Name“ : “TK2323 Burger”
}
{
“Delicious“ : false
}

76. 76 JSON
▹An array (in square brackets) ▹An object (in curly braces)
76
{
“Courses” : [ “TK2323”, “TR2312”,
“TP4345”]
}
“Student”: {
"name":“Ali",
"age":30,
“Matrix No":”A111111”
}

77. 77 JSON: Nested
▹List of objects inside an array
▹A “books” object contains array of “language”, “edition”
and “lastName” object
77

78. 78 JSON

79. Firebase Realtime
Database
Store and sync data in real time across all connected clients
79

80. Firebase – Instantiate80
private FirebaseAuth mFirebaseAuth;
private FirebaseUser mFirebaseUser;
private DatabaseReference mDatabase;
// Initialize Firebase Auth and Database Reference
mFirebaseAuth = FirebaseAuth.getInstance();
mFirebaseUser = mFirebaseAuth.getCurrentUser();
mUserId = mFirebaseUser.getUid();
mDatabase = FirebaseDatabase.getInstance().getReference();

81. Firebase – Ways to Save Data81
Set Write or replace data to a defined path,
like messages/users/<username>
update Update some of the keys for a defined path without replacing all
of the data
push
(append)
Add to a list of data in the database. Every time you push a new
node onto a list, your database generates a unique key,
like messages/users/<unique-user-id>/<username>
transaction Use our transactions feature when working with complex data
that could be corrupted by concurrent updates

82. Firebase – Add Data82
btt_add.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
Task task = new Task(et_new_task.getText().toString());
mDatabase.child("users").child(mUserId).child("tasks").push().setValue(task);
Intent intent = new Intent(AddTask.this, MainActivity.class);
startActivity(intent);
}
});

83. Firebase – Add Data83

84. Firebase – Read84
final Button btt_read = (Button) findViewById(R.id.add_task_btt_read);
btt_read.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
mDatabase.addValueEventListener(new ValueEventListener() {
//This method will be called with a snapshot of the data at this location.
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
String temp = String.valueOf(dataSnapshot.child("users").child(mUserId)
.child("tasks").getChildrenCount());
Toast.makeText(AddTask.this,“Count: "+temp,Toast.LENGTH_SHORT).show();
for (DataSnapshot postSnapshot: dataSnapshot.child("users").child(mUserId)
.child("tasks").child("-KW7tEHNtDfuc5NEOkvk").getChildren()) {
Toast.makeText(AddTask.this,“Data:"+ postSnapshot.toString(),Toast.LENGTH_LONG).show();
}
}@Override
.
.
.

85. Firebase – Read85
listView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
@Override
public boolean onItemLongClick(AdapterView<?> adapterView, View view, int position, long l) {
Toast.makeText(MainActivity.this, "item:" + listView.getItemAtPosition(position),
Toast.LENGTH_LONG).show();
mDatabase.child("users").child(mUserId).child("tasks") //Select from users -> tasks
.orderByChild("title") //Where title =
.equalTo((String) listView.getItemAtPosition(position)) //"return the string"
.addListenerForSingleValueEvent(new ValueEventListener() { //Add a listener for a single change in
the data at this location. This listener will be triggered once with the value of the data at the location.
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.hasChildren()) {
// Data is ordered by increasing height, so we want the first entry
DataSnapshot firstChild = dataSnapshot.getChildren().iterator().next();
firstChild.getRef().removeValue(); //Set the value at this location to 'null'
Toast.makeText(MainActivity.this, "Task Removed", Toast.LENGTH_SHORT).show();
}
}

86. 8686
▹SQL queries equivalent in
Firebase
Firebase Realtime Database

87. 87
Firebase –
Read
87
UID (PK) Name Email Age Location
1 “David” “davi@email.com 99 SF
9 “Alice” “alice@email.com 28 Berlin

88. 88 Firebase – Read
Select a user by UID
SELECT * FROM Users WHERE UID = 1;
const rootRef = firebase.database.ref();
const dataRef = rootRef.child(‘users’).child(‘1);
88
UID (PK) Name Email Age Location
1 “David” “davi@email.com 99 SF
9 “Alice” “alice@email.com 28 Berlin

89. 89 Firebase – Read
Select a user by email address
SELECT * FROM Users WHERE Email = ‘alice@email.com’;
const dataRef =
rootRef.child(‘users’).orderByChild(‘email’).equalTo(‘alice@email.com’);
89
UID (PK) Name Email Age Location
1 “David” “davi@email.com 99 SF
9 “Alice” “alice@email.com 28 Berlin

90. 90 Firebase – Read
Limit to 10 Users
SELECT * FROM Users LIMIT 10;
const dataRef = rootRef.child(‘users’).limitToFirst(10);
90
UID (PK) Name Email Age Location
1 “David” “davi@email.com 99 SF
9 “Alice” “alice@email.com 28 Berlin

91. 91 Firebase – Read
Get all users names that start with ‘D’
SELECT * FROM Users WHERE Name Like ‘D%’;
const dataRef =
rootRef.child(‘users’).orderByChild(‘name’).startAt(‘D’).endAt(‘Duf8ff’);
91
UID (PK) Name Email Age Location
1 “David” “davi@email.com 99 SF
9 “Alice” “alice@email.com 28 Berlin
10 “Ravi” “ravi@email.com” 35 Kuala Lumpur

92. 92 Firebase – Read
Get all users who are less than age 50
SELECT * FROM Users WHERE Age < 50;
const dataRef = rootRef.child(‘users’).orderByChild(‘age’).endAt(49);
92
UID (PK) Name Email Age Location
1 “David” “davi@email.com 99 SF
9 “Alice” “alice@email.com 28 Berlin

93. 93 Firebase – Read
Get all users who are greater than age 50
SELECT * FROM Users WHERE Age > 50;
const dataRef = rootRef.child(‘users’).orderByChild(‘age’).startAt(51);
93
UID (PK) Name Email Age Location
1 “David” “davi@email.com 99 SF
9 “Alice” “alice@email.com 28 Berlin

94. 94 Firebase – Read
Get all users who are between 20 and 100
SELECT * FROM Users WHERE Age >= 20 & Age <= 100 ;
const dataRef =
rootRef.child(‘users’).orderByChild(‘age’).startAt(20).endAt(100);
94
UID (PK) Name Email Age Location
1 “David” “davi@email.com 99 SF
9 “Alice” “alice@email.com 28 Berlin

95. 95 Firebase – Read
Get all users who are 28 and live in Berlin
SELECT * FROM Users WHERE Age = 28 AND Location = ‘Berlin’;
const dataRef =
rootRef.child(‘users’).orderByChild(‘age_location’).equalTo(’28_Berlin’);
95
UID (PK) Name Email Age Location
1 “David” “davi@email.com 99 SF
9 “Alice” “alice@email.com 28 Berlin

96. 96
▹Example
DataSnapshot

97. Firebase – Update/Replace
Data97
btt_update.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
final Task task = new Task(et_new_task.getText().toString());
mDatabase.child("users").child(mUserId)
.child("tasks").orderByChild("title") //Where title =
.equalTo(et_old_task.getText().toString()).addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.hasChildren()) {
DataSnapshot firstChild = dataSnapshot.getChildren().iterator().next();
firstChild.getRef().setValue(task); //Set the value at this location to 'null'
}
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
});

98. DataSnapshot
▹ A DataSnapshot instance contains data from a
Firebase Database location.
▹ Any time you read Database data, you receive the
data as a DataSnapshot.
98

99. DataSnapshot
▹ DataSnapshots are passed to the methods in
listeners that you attach with
▹ addValueEventListener(ValueEventListener),
▹ addChildEventListener(ChildEventListener), or
▹ addListenerForSingleValueEvent(ValueEventListene
r).
99

100. Event Listener
▹ addValueEventListener(ValueEventListener)
▹ Read the data from the specific location
▹ addChildEventListener(ChildEventListener),
▹ Read the data from the child location
▹ addListenerForSingleValueEvent(ValueEventListene
r).
▹ Read only once
100

101. Firebase – Read101
final Button btt_read = (Button) findViewById(R.id.add_task_btt_read);
btt_read.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
mDatabase.addValueEventListener(new ValueEventListener() {
//This method will be called with a snapshot of the data at this location.
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
String temp = String.valueOf(dataSnapshot.child("users").child(mUserId)
.child("tasks").getChildrenCount());
Toast.makeText(AddTask.this,“Count: "+temp,Toast.LENGTH_SHORT).show();
for (DataSnapshot postSnapshot: dataSnapshot.child("users").child(mUserId)
.child("tasks").child("-KW7tEHNtDfuc5NEOkvk").getChildren()) {
Toast.makeText(AddTask.this,“Data:"+ postSnapshot.toString(),Toast.LENGTH_LONG).show();
}
}@Override
.
.
.

102. Firebase – Read102
listView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
@Override
public boolean onItemLongClick(AdapterView<?> adapterView, View view, int position, long l) {
Toast.makeText(MainActivity.this, "item:" + listView.getItemAtPosition(position),
Toast.LENGTH_LONG).show();
mDatabase.child("users").child(mUserId).child("tasks") //Select from users -> tasks
.orderByChild("title") //Where title =
.equalTo((String) listView.getItemAtPosition(position)) //"return the string"
.addListenerForSingleValueEvent(new ValueEventListener() { //Add a listener for a single change in
the data at this location. This listener will be triggered once with the value of the data at the location.
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.hasChildren()) {
// Data is ordered by increasing height, so we want the first entry
DataSnapshot firstChild = dataSnapshot.getChildren().iterator().next();
firstChild.getRef().removeValue(); //Set the value at this location to 'null'
Toast.makeText(MainActivity.this, "Task Removed", Toast.LENGTH_SHORT).show();
}
}

103. Firebase – Add Data103
btt_add.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
String id = databaseClubs.push().getKey();
// creat the club object
Club newClub = new Club(id,code,name);
// save the club information into the firebase
databaseClubs.child(id).setValue(newClub);
}
});

104. Firebase – Add Data104