A brief description and short example of Android Data Binding from version 6 and above, along with a brief description of Butterknife (by Jake Wharton).

1. Android Data Binding in Android
Lollipop and Beyond
Oswald Campesato
Consultant/Training:
www.iquarkt.com
ocampesato@yahoo.com

2. Standard Android Data Binding (<v6)
• 1) Specify a value for the id attribute of a widget
via the “@+id” syntax in activity_main.xml
• 2) Use findViewById() in onCreate() to locate
Android widgets in activity_main.xml

3. Sample activity_main.xml (<v6)
• <Button android:id="@+id/button1"
• android:layout_width="fill_parent"
• android:layout_height="wrap_content"
• android:layout_alignParentBottom="true"
• android:text="@string/clickme" />
•
• <TextView
• android:layout_width="fill_parent"
• android:layout_height="wrap_content"
• android:text="@string/hello"
• android:layout_above="@id/button1"
• />

4. findViewById() in MainActivity
public class MainActivity extends Activity
{
private Button myButton = null;
private String TAG = "myButton";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
this.myButton = (Button)this.findViewById(R.id.button1);
}

5. Android Data Binding (v6 or higher)
1) Define the Java User class (written by you)
2) Add a <layout> element with a child <data> element
<layout
xmlns:android="http://schemas.android.com/apk/res/android">
<data> <variable name="user” type="com.example.User"/>
</data>
3) add the following in the android block in build.gradle:
android {
. . .
dataBinding.enabled = true
}
4) change the inflater code in onCreate()

6. New activity_main.xml (v>=6)
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android=
"http://schemas.android.com/apk/res/android">
<data> <variable name="user" type="com.example.User"/> </data>
<LinearLayout
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@{user.firstName}"/>
</LinearLayout>
</layout>

7. Contents of User class
package com.example.oswaldcampesato2.mybinding1;
public class User {
private String firstName = "Dave";
private String lastName = "Smith";
public User() {};
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getFirstName() { return firstName; }
}

8. New Inflater Code
ActivityMainBinding binding =
DataBindingUtil.setContentView(
this, R.layout.activity_main);
The ActivityMainBinding class matches the file:
activity_main.xml
Another example:
ActivityUserBinding matches activity_user.xml

9. Android Studio 2.2 (version 7)
Error message: "Failed to resolve:
com.android.support.constraint:constraint-layout:1.0.0-alpha4"
Solution:
1) Download Android Studio 2.2 Preview 7
2) Update SDK Tools to the latest 25.2.1
3) Download ConstraintLayout & Solver for ConstraintLayout in SDK
Manager
4) Add com.android.support.constraint:constraint-layout:1.0.0-alpha5 to
gradle.build
More details:
• http://stackoverflow.com/questions/38450414/error30-13-failed-to-
resolve-com-android-support-constraintconstraint-layo

10. Android Studio 2.2 (version 7)
1) build.gradle:
classpath 'com.android.tools.build:gradle:2.2.0-alpha7'
2) gradle-wrapper.properties:
distributionUrl=https://services.gradle.org/distributions/gradle-
2.14.1-all.zip
3) gradle.build:
com.android.support.constraint:constraint-layout:1.0.0-alpha5
[Downloads: http://services.gradle.org/distributions]

11. What about ButterKnife?
Created by Jake Wharton
Uses binding annotation
https://github.com/JakeWharton/butterknife

12. Sample Annotations (1)
class ExampleActivity extends Activity {
@BindView(R.id.user) EditText username;
@BindView(R.id.pass) EditText password;
@BindString(R.string.login_error) String
loginErrorMessage;
@OnClick(R.id.submit) void submit() {
// ...
}
...
}

13. Build.gradle (project-level)
buildscript {
repositories {
mavenCentral()
}
dependencies {
classpath
'com.neenbedankt.gradle.plugins:android-apt:1.8'
}
}

14. Build.gradle (module-level)
apply plugin: 'android-apt'
android {
...
}
dependencies {
compile 'com.jakewharton:butterknife:8.2.1'
apt 'com.jakewharton:butterknife-compiler:8.2.1'
}

15. Sample Annotations (2)
@Override public void onCreate(Bundle
savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.simple_activity);
ButterKnife.bind(this);
// TODO Use fields...
}

16. Android Studio 2.0 Installation
• 1) Launch error for Android Studio:
“'tools.jar' seems to be not in Android Studio classpath.
Please ensure JAVA_HOME points to JDK rather than JRE.”
Option #1: use Java8
Option #2: copy tools.jar from $JAVA_HOME/lib into
/Applications/AndroidStudio.app/Content/lib
• 2) Incorrect permissions for Android Studio:
Log path '/Users/…/Library/Logs/AndroidStudio2.1' is
inaccessible.
Solution: chmod 775 $HOME/…/AndroidStudio2.1

17. Android Studio 2.0 Installation
3) Internal Error. Please report to
https://https://code.google.com/p/android/issues
java.lang.RuntimeException:
com.intellij.ide.plugins.PluginManager$StartupAbortedExcep
tion: Fatal error initializing
'com.android.tools.idea.AndroidInitialConfigurator'
Solution: download/install this version of AS:
http://tools.android.com/download/studio/builds/2-0-preview-
3b
4) Error: LSOpenURLsWithRole() failed with error -10810 for
the file /Applications/Android Studio.app.

18. Recent/Upcoming Books and Training
1) HTML5 Canvas and CSS3 Graphics (2013)
2) jQuery, CSS3, and HTML5 for Mobile (2013)
3) HTML5 Pocket Primer (2013)
4) jQuery Pocket Primer (2013)
5) HTML5 Mobile Pocket Primer (2014)
6) D3 Pocket Primer (2015)
7) Python Pocket Primer (2015)
8) SVG Pocket Primer (2016)
9) CSS3 Pocket Primer (2016)
10) Angular 2 Pocket Primer (2017)