The document discusses how Data Binding works in Android and its advantages over traditional MVP patterns. It explains that Data Binding allows binding UI components in XML layouts to data sources like ViewModels, avoiding "glue code". This improves testability and maintainability. It provides examples of using Data Binding expressions to bind EditText values two-way to a ViewModel property using InverseBindingAdapters.

1. Yongjun Kim, kakaobank
@imkimkevin
Seoul
Android DataBinding
UI Modularization, ViewModel and Testing

2. AGENDA
Korea
● The reasons to use Data Binding
● How Data Binding works
● UI Modularization
● Unit Testing

3. Warming UP!
https://www.pexels.com

5. as Android Developer
Activity (Fragment, View)
Drawing UI
Receiving User Interactions Service Broadcast Receiver Content Provider
UI

6. as Android Developer
Activity (Fragment, View)
Drawing UI
Receiving User Interactions Service Broadcast Receiver Content Provider
ViewModel
Repository
Presenter
And more…as API Developer
Use Case
Business
UI
Provides
APIs

7. as Android Developer
Activity (Fragment, View)
Drawing UI
Receiving User Interactions Service Broadcast Receiver Content Provider
ViewModel
Repository
Presenter
And more…as API Developer
Use Case
Business
UI
Provides
APIs
Testable Code

8. as Android Developer
Activity (Fragment, View)
Drawing UI
Receiving User Interactions Service Broadcast Receiver Content Provider
ViewModel
Repository
Presenter
And more…as API Developer
Use Case
Business
UI
Provides
APIs
Testable Code
Presenter

9. The reasons to use
Data Binding
Seoul

10. The past : Model-View-Presenter
fun setTitleText(title: String) {
titleText.text = title
}
fun setTitleVisible(visible: Boolean) {
titleText.visibility = if (visible)
View.VISIBLE else View.GONE
}
fun setButtonEnabled(enable: Boolean) {
titleText.isEnabled = enable
}
Activity Presenter
fun init() {
if (isFirstLogin) {
view.setTitleText("Welcome To DevFest 2018")
view.setTitleVisible(true)
}
}
fun validateDateOfBirth(number: String) {
view.setButtonEnabled(number.length >= 6)
}
.
.
.

11. The past : Model-View-Presenter
Activity Presenter
fun init() {
if (isFirstLogin) {
view.setTitleText("Welcome To DevFest 2018")
view.setTitleVisible(true)
}
}
fun validateDateOfBirth(number: String) {
view.setButtonEnabled(number.length >= 6)
}
Giant Glue Code
if (isFirstLogin) {
view.setTitleText("Welcome To DevFest 2018")
view.setTitleVisible(true)
}
view.setButtonEnabled(number.length >= 6)
fun setTitleText(title: String) {
titleText.text = title
}
fun setTitleVisible(visible: Boolean) {
titleText.visibility = if (visible)
View.VISIBLE else View.GONE
}
fun setButtonEnabled(enable: Boolean) {
titleText.isEnabled = enable
}
.
.
.

12. So far, It s ok
BusinessUI
Activity
Activity
PresenterActivity
Presenter
Presenter

13. So far, It s ok
one to one
but testable
BusinessUI
Activity
Activity
PresenterActivity
Presenter
Presenter

14. So far, It s ok
one to one
but testable
non-reusable
can be solved by
- use case
- abstraction
BusinessUI
Activity
Activity
PresenterActivity
Presenter
Presenter

15. So far, It s ok
one to one
but testable
non-reusable
can be solved by
- use case
- abstraction
hard to maintain
BusinessUI
Activity
Activity
PresenterActivity
Presenter
Presenter
- abstraction

16. DataBinding
● ?
"16
https://unsplash.com

18. android {
. . .
dataBinding {
enabled = true
}
}
build.gradle in app module
$gradle_version = Android Plugin for Gradle 1.5.0-alpha1 and higher
android_studio_version = Android Studio 1.3 and higher
// For Kotlin
dependencies {
kapt “com.android.databinding:compiler:$gradle_version"
}

19. Sample Application

20. Sample Application

21. TextView
Welcome message
for Devfest Seoul of the year
Requirements
EditText
6 numbers for authentication Button
Enabled for login
with 6 numbers

22. override fun onCreate(savedInstanceState: Bundle?) {
...
setContentView(R.layout.activity_main)
textView.text = String.format(getString(R.string.title), presenter.year)
editText.addTextChangedListener(object : TextWatcher {
override fun beforeTextChanged(...) { }
override fun afterTextChanged(s: Editable?) {
presenter.validate(s.toString())
}
override fun onTextChanged(...) { }
})
button.setOnClickListener { }
}
fun setButtonEnabled(enable: Boolean) {
button.isEnabled = enable
}
Activity

23. String.format(getString(R.string.title), presenter.year)
override fun onCreate(savedInstanceState: Bundle?) {
...
setContentView(R.layout.activity_main)
textView.text = String.format(getString(R.string.title), presenter.year)
editText.addTextChangedListener(object : TextWatcher {
override fun beforeTextChanged(...) { }
override fun afterTextChanged(s: Editable?) {
presenter.validate(s.toString())
}
override fun onTextChanged(...) { }
})
button.setOnClickListener { }
}
fun setButtonEnabled(enable: Boolean) {
button.isEnabled = enable
}
“Welcome to Devfest Seoul %s”
Activity

24. override fun onCreate(savedInstanceState: Bundle?) {
...
setContentView(R.layout.activity_main)
textView.text = String.format(getString(R.string.title), presenter.year)
editText.addTextChangedListener(object : TextWatcher {
override fun beforeTextChanged(...) { }
override fun afterTextChanged(s: Editable?) {
presenter.validate(s.toString())
}
override fun onTextChanged(...) { }
})
button.setOnClickListener { }
}
fun setButtonEnabled(enable: Boolean) {
button.isEnabled = enable
}
presenter.year
presenter.validate(s.toString())
fun validate(number: String) {
view.setButtonEnabled(number.isCodeValid())
}
Activity Presenter

25. override fun onCreate(savedInstanceState: Bundle?) {
...
setContentView(R.layout.activity_main)
textView.text = String.format(getString(R.string.title), presenter.year)
editText.addTextChangedListener(object : TextWatcher {
override fun beforeTextChanged(...) { }
override fun afterTextChanged(s: Editable?) {
presenter.validate(s.toString())
}
override fun onTextChanged(...) { }
})
button.setOnClickListener { }
}
fun setButtonEnabled(enable: Boolean) {
button.isEnabled = enable
}
presenter.year
presenter.validate(s.toString())
fun validate(number: String) {
view.setButtonEnabled(number.isCodeValid())
}
fun setButtonEnabled(enable: Boolean) {
button.isEnabled = enable
}
Activity Presenter

26. Activity
view xml
Presenter
Data Binding
MVP with Data Binding

27. override fun onCreate(savedInstanceState: Bundle?) {
...
setContentView(R.layout.activity_main)
textView.text = String.format(getString(R.string.title), presenter.year)
editText.addTextChangedListener(object : TextWatcher {
override fun beforeTextChanged(...) { }
override fun afterTextChanged(s: Editable?) {
presenter.validate(s.toString())
}
override fun onTextChanged(...) { }
})
button.setOnClickListener { }
}
fun setButtonEnabled(enable: Boolean) {
button.isEnabled = enable
}
Activity Presenterxml Data Binding

28. override fun onCreate(savedInstanceState: Bundle?) {
...
setContentView(R.layout.activity_main)
textView.text = String.format(getString(R.string.title), presenter.year)
editText.addTextChangedListener(object : TextWatcher {
override fun beforeTextChanged(...) { }
override fun afterTextChanged(s: Editable?) {
presenter.validate(s.toString())
}
override fun onTextChanged(...) { }
})
button.setOnClickListener { }
}
fun setButtonEnabled(enable: Boolean) {
button.isEnabled = enable
}
setContentView(R.layout.activity_main)
val binding = DataBindingUtil.setContentView<ActivityMainBinding>(
this, R.layout.activity_main)
binding.setLifecycleOwner(this) // LiveData
binding.setPresenter(presenter)
Activity Presenterxml Data Binding
val binding = DataBindingUtil.setContentView<ActivityMainBinding>(
this, R.layout.activity_main)
binding.setLifecycleOwner(this) // LiveData

29. override fun onCreate(savedInstanceState: Bundle?) {
...
setContentView(R.layout.activity_main)
textView.text = String.format(getString(R.string.title), presenter.year)
editText.addTextChangedListener(object : TextWatcher {
override fun beforeTextChanged(...) { }
override fun afterTextChanged(s: Editable?) {
presenter.validate(s.toString())
}
override fun onTextChanged(...) { }
})
button.setOnClickListener { }
}
fun setButtonEnabled(enable: Boolean) {
button.isEnabled = enable
}
setContentView(R.layout.activity_main)
val binding = DataBindingUtil.setContentView<ActivityMainBinding>(
this, R.layout.activity_main)
binding.setLifecycleOwner(this) // LiveData
binding.setPresenter(presenter)
<layout>
<android.support.constraint.ConstraintLayout …>
<TextView
android:id=“@+id/textView" ... />
<EditText
android:id=“@+id/editText" ... />
<Button
android:id=“@+id/button" ... />
</android.support.constraint.ConstraintLayout>
</layout>
<layout>
</layout>
R.layout.activity_main
Activity Presenterxml Data Binding

30. override fun onCreate(savedInstanceState: Bundle?) {
...
setContentView(R.layout.activity_main)
textView.text = String.format(getString(R.string.title), presenter.year)
editText.addTextChangedListener(object : TextWatcher {
override fun beforeTextChanged(...) { }
override fun afterTextChanged(s: Editable?) {
presenter.validate(s.toString())
}
override fun onTextChanged(...) { }
})
button.setOnClickListener { }
}
fun setButtonEnabled(enable: Boolean) {
button.isEnabled = enable
}
setContentView(R.layout.activity_main)
val binding = DataBindingUtil.setContentView<ActivityMainBinding>(
this, R.layout.activity_main)
binding.setLifecycleOwner(this) // LiveData
binding.setPresenter(presenter)binding.setPresenter(presenter)
<layout>
<data>
<variable
name=“presenter” type=“com...MainPresenter"/>
</data>
<android.support.constraint.ConstraintLayout …>
<EditText
android:id=“@+id/editText" ... />
<data>
<variable
name=“presenter” type=“com...MainPresenter"/>
</data>
Activity Presenterxml Data Binding

31. delete
override fun onCreate(savedInstanceState: Bundle?) {
...
val binding = DataBindingUtil.setContentView<ActivityMainBinding>(
this, R.layout.activity_main)
binding.setLifecycleOwner(this)
binding.setPresenter(presenter)
textView.text = String.format(getString(R.string.title), presenter.year)
editText.addTextChangedListener(object : TextWatcher {
override fun beforeTextChanged(...) { }
override fun afterTextChanged(s: Editable?) {
presenter.validate(s.toString())
}
override fun onTextChanged(...) { }
})
button.setOnClickListener { }
}
fun setButtonEnabled(enable: Boolean) {
button.isEnabled = enable
}
Activity Presenterxml Data Binding

32. https://www.pexels.com

33. Activity Presenterxml Data Binding
override fun onCreate(savedInstanceState: Bundle?) {
...
val binding = DataBindingUtil.setContentView<ActivityMainBinding>(
this, R.layout.activity_main)
binding.setLifecycleOwner(this)
binding.setPresenter(presenter)
textView.text = String.format(getString(R.string.title), presenter.year)
editText.addTextChangedListener(object : TextWatcher {
override fun beforeTextChanged(...) { }
override fun afterTextChanged(s: Editable?) {
presenter.validate(s.toString())
}
override fun onTextChanged(...) { }
})
button.setOnClickListener { }
}
fun setButtonEnabled(enable: Boolean) {
button.isEnabled = enable
}
<TextView
<layout>
...
<android.support.constraint.ConstraintLayout ...>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text=“@{@string/title(presenter.year)}” />android:text=“@{@string/title(presenter.year)}”
textView.text = String.format(getString(R.string.title), presenter.year)
TextView

34. android:text=“@{@string/title(presenter.year)}”
Expression Language

35. android:text="@{String.valueOf(index + 1)}"
android:visibility="@{size < 15 ? View.GONE : View.VISIBLE}”
android:textColor=“@{colorText}” ???
android:text=“@{@string/title(presenter.year)}”
Expression Language

36. android:textColor=“#fe3dfc”
@InverseMethod

37. colorText.value = "#000000"
android:textColor=“#fe3dfc”
android:textColor=“@{colorText}”
@InverseMethod

38. android:textColor=“#fe3dfc”
android:textColor=“@{colorText}” // ERROR!!
@InverseMethod
colorText.value = "#000000"

39. object Converters {
@JvmStatic
@InverseMethod(“toColor")
fun fromColorString(colorString: String): Int {
return Color.parseColor(colorString)
}
@JvmStatic // Two-way Binding
fun toColor(color: Int): String {
return color.toString()
}
}
android:textColor="@{Converters.fromColorString(colorText)}"
@InverseMethod

40. android:text="@{String.valueOf(index + 1)}"
android:visibility="@{size < 15 ? View.GONE : View.VISIBLE}”
android:textColor=“@{colorText}” // @InverseMethod
android:visibility=“@{title != null}” ???
android:text=“@{@string/title(presenter.year)}”
Expression Language

41. android:visibility=“@{title != null}”
visible | invisible | gone
@BindingConversion
object Conversions {
@JvmStatic
@BindingConversion
fun convertBooleanToVisibility(visible: Boolean)
= if (visible) View.VISIBLE else View.GONE
}

42. android:visibility=“@{title != null}”
visible | invisible | gone
Normally
1. visible | invisible ???
2. visible | gone ???

43. android:visibility=“@{title != null}”
visible | invisible | gone
Normally
1. visible | invisible
2. visible | gone
app:visible=“@{title != null}”
app:visibleOrGone=“@{title != null}”

44. @BindingAdapter
@Target(ElementType.METHOD)
public @interface BindingAdapter {
String[] value();
boolean requireAll() default true;
}

45. @BindingAdapter
@Target(ElementType.METHOD)
public @interface BindingAdapter {
String[] value();
boolean requireAll() default true;
}
// Example
@BindingAdapter("visible")
@BindingAdapter(value={"url", "size"},
requireAll=false)

46. app:visible=“@{title != null}”
app:visibleOrGone=“@{title != null}”
@BindingAdapter
@JvmStatic
@BindingAdapter("visible")
fun View.setVisible(visible: Boolean) {
visibility = if (visible) View.VISIBLE else View.INVISIBLE
}
@JvmStatic
@BindingAdapter("visibleOrGone")
fun View.setVisibleOrGone(visible: Boolean) {
visibility = if (visible) View.VISIBLE else View.GONE
}

47. Activity Presenterxml Data Binding
override fun onCreate(savedInstanceState: Bundle?) {
...
val binding = DataBindingUtil.setContentView<ActivityMainBinding>(
this, R.layout.activity_main)
binding.setLifecycleOwner(this)
binding.setPresenter(presenter)
editText.addTextChangedListener(object : TextWatcher {
override fun beforeTextChanged(...) { }
override fun afterTextChanged(s: Editable?) {
presenter.validate(s.toString())
}
override fun onTextChanged(...) { }
})
button.setOnClickListener { }
}
fun setButtonEnabled(enable: Boolean) {
button.isEnabled = enable
}
editText.addTextChangedListener(object : TextWatcher {
override fun beforeTextChanged(...) { }
override fun afterTextChanged(s: Editable?) {
presenter.validate(s.toString())
}
override fun onTextChanged(...) { }
})
<layout>
...
<android.support.constraint.ConstraintLayout ...>
<EditText
android:id=“@+id/editText"
android:text=“@={presenter.authCode}”android:text=“@={presenter.authCode}”
EditText
class MainPresenter {
val authCode = MutableLiveData<String>()
...
}

48. android:text=“@={presenter.authCode)}”
Two-way data binding

49. android:text=“@={presenter.authCode)}”
Two-way data binding
OK
presenter.authCode = null

50. android:text=“@={presenter.authCode)}”
Two-way data binding
OKOK
123456 presenter.authCode = “123456”

51. android:text=“@={presenter.authCode)}”
Two-way data binding
OK
1234
OK
presenter.authCode = “1234”

52. android:text=“@={presenter.authCode)}”
InverseBindingAdapter in ActivityMainBinding.java
@InverseBindingAdapter(attribute = "android:text",
event = "android:textAttrChanged")
public static String getTextString(TextView view) {
return view.getText().toString();
}

53. android:text=“@={presenter.authCode)}”
TextViewBindingAdapter.setTextWatcher(this.editText,
null, null, null, editTextandroidTextAttrChanged);
BindingAdapter in ActivityMainBinding.java
private InverseBindingListener editTextandroidTextAttrChanged
= new InverseBindingListener() {
@Override
public void onChange() {
String callbackArg_0 =
TextViewBindingAdapter.getTextString(editText);
...
vmAuthCode.setValue(((String) (callbackArg_0)));
}
editTextandroidTextAttrChanged

54. android:text=“@={presenter.authCode)}”
TextViewBindingAdapter.setTextWatcher(this.editText,
null, null, null, editTextandroidTextAttrChanged);
BindingAdapter in ActivityMainBinding.java
private InverseBindingListener editTextandroidTextAttrChanged
= new InverseBindingListener() {
@Override
public void onChange() {
String callbackArg_0 =
TextViewBindingAdapter.getTextString(editText);
...
vmAuthCode.setValue(((String) (callbackArg_0)));
}
editTextandroidTextAttrChanged
TextViewBindingAdapter.getTextString(editText);

55. android:text=“@={presenter.authCode)}”
TextViewBindingAdapter.setTextWatcher(this.editText,
null, null, null, editTextandroidTextAttrChanged);
BindingAdapter in ActivityMainBinding.java
TextViewBindingAdapter.setTextWatcher
@BindingAdapter(value = {"android:beforeTextChanged", "android:onTextChanged",
"android:afterTextChanged", "android:textAttrChanged"}, requireAll = false)
public static void setTextWatcher(TextView view, final BeforeTextChanged before,
final OnTextChanged on, final AfterTextChanged after,
final InverseBindingListener textAttrChanged) {
final TextWatcher newValue;
...
newValue = new TextWatcher() {
...
@Override
public void onTextChanged(CharSequence s, int start, int before, int count)
if (textAttrChanged != null) {
textAttrChanged.onChange();

56. android:text=“@={presenter.authCode)}”
Default BindingAdapters
android.databinding.adapters
@BindingMethods({
@BindingMethod(type = TextView.class, attribute =
"android:inputType", method = "setRawInputType"),
@BindingMethod(type = TextView.class, attribute =
"android:textAllCaps", method = “setAllCaps"),
...
})
public class TextViewBindingAdapter {
@BindingAdapter("android:text")
public static void setText(TextView view, CharSequence text) {
final CharSequence oldText = view.getText();
if (text == oldText || (text == null && oldText.length() == 0)) {
return;
}

57. Activity Presenterxml Data Binding
override fun onCreate(savedInstanceState: Bundle?) {
...
val binding = DataBindingUtil.setContentView<ActivityMainBinding>(
this, R.layout.activity_main)
binding.setLifecycleOwner(this)
binding.setPresenter(presenter)
button.setOnClickListener { }
}
fun setButtonEnabled(enable: Boolean) {
button.isEnabled = enable
}
button.setOnClickListener { }
fun setButtonEnabled(enable: Boolean) {
button.isEnabled = enable
}
<Button
…
android:enabled="@{ValidationUtil.isCodeValid(vm.authCode)}"
android:onClick="@{() -> vm.login()}"
<layout>
<data>
<import type=“com....ValidationUtil"/>
<variable
<import type=“com....ValidationUtil"/>
object ValidationUtil {
@JvmStatic
fun String?.isCodeValid() = this?.length ?: 0 >= 6
}

58. class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
val binding = DataBindingUtil.setContentView<ActivityMainBinding>(
this, R.layout.activity_main)
binding.setLifecycleOwner(this)
binding.setPresenter(presenter)
}
}
Activity

59. Activity xml
<layout>
<data>
<import type=“com....ValidationUtil"/>
<variable name=“presenter” type=“com...MainPresenter"/>
</data>
<android.support.constraint.ConstraintLayout ...>
<TextView
android:text=“@{@string/title(presenter.year)}” .../>
<EditText
android:text=“@={presenter.authCode}” .../>
<Button
android:enabled=“@{ValidationUtil.isCodeValid(presenter.authCode)}”
android:onClick="@{() -> presenter.login()}” .../>
</android.support.constraint.ConstraintLayout>
</layout>

60. class MainPresenter {
var year : String
val authCode = MutableLiveData<String>()
init {
year = "2018"
}
fun login() {
// do something!
}
}
Activity Presenterxml Data Binding

61. Activity
view xml
Presenter
Data Binding
AS-IS : MVP with Data Binding

62. class MainViewModel {
var year : String
val authCode = MutableLiveData<String>()
init {
year = "2018"
}
fun login() {
// do something!
}
}
Activity ViewModelxml Data Binding

63. TO-BE : MVVM with Data Binding
Activity
view xml
ViewModel
Data Binding

64. How DataBinding works
Seoul

65. OK
<android.support.constraint.ConstraintLayout ...>
...
<EditText
android:id=“@+id/editText“
android:text=“@={vm.authCode}” .../>
<Button
android:id=“@+id/button“
android:enabled="@{ValidationUtil.isCodeValid(vm.authCode)}"

66. OK
OK
123456
<android.support.constraint.ConstraintLayout ...>
...
<EditText
android:id=“@+id/editText“
android:text=“@={vm.authCode}” .../>
<Button
android:id=“@+id/button“
android:enabled="@{ValidationUtil.isCodeValid(vm.authCode)}"

67. OK
OK
123456
<android.support.constraint.ConstraintLayout ...>
...
<EditText
android:id=“@+id/editText“
android:text=“@={vm.authCode}” .../>
<Button
android:id=“@+id/button“
android:enabled="@{ValidationUtil.isCodeValid(vm.authCode)}"
How this works in generated class?

68. OK
OK
123456
<android.support.constraint.ConstraintLayout ...>
...
<EditText
android:id=“@+id/editText“
android:text=“@={vm.authCode}” .../>
<Button
android:id=“@+id/button“
android:enabled="@{ValidationUtil.isCodeValid(vm.authCode)}"
DirtyFlag

69. activity_main.xml
<layout>
<data>
<import type=“com....ValidationUtil"/>
<variable name=“vm” type=“com...MainViewModel"/>
</data>
<android.support.constraint.ConstraintLayout ...>
<TextView
android:text=“@{@string/title(vm.year)}” .../>
<EditText
android:text=“@={presenter.authCode}” .../>
<Button
android:enabled=“@{ValidationUtil.isCodeValid(vm.authCode)}”
android:onClick="@{() -> vm.login()}” .../>
</android.support.constraint.ConstraintLayout>
</layout>

70. activity_main.xml Layout Processor
<layout>
<data>
<import type=“com....ValidationUtil"/>
<variable name=“vm” type=“com...MainViewModel"/>
</data>
<android.support.constraint.ConstraintLayout ...>
<TextView
android:text=“@{@string/title(vm.year)}” .../>
<EditText
android:text=“@={presenter.authCode}” .../>
<Button
android:enabled=“@{ValidationUtil.isCodeValid(vm.authCode)}”
android:onClick="@{() -> vm.login()}” .../>
</android.support.constraint.ConstraintLayout>
</layout>

71. ActivityMainBinding.java Layout Processor
public class ActivityMainTestBinding extends android.databinding.ViewDataBinding implements
android.databinding.generated.callback.OnClickListener.Listener {
...
@NonNull
public final android.widget.Button button;
@NonNull
public final android.widget.EditText editText;
@NonNull
public final android.widget.TextView textView;
@NonNull
private final android.support.constraint.ConstraintLayout mboundView0;
@Nullable
private com.github.kimkevin.devfestseoul18.MainViewModel mVm;
@Nullable
private final android.view.View.OnClickListener mCallback1;
Variable
Listener
View
@NonNull
public final android.widget.Button button;
@NonNull
public final android.widget.EditText editText;
@NonNull
public final android.widget.TextView textView;
@Nullable
private com.github.kimkevin.devfestseoul18.MainViewModel mVm;
@Nullable
private final android.view.View.OnClickListener mCallback1;
ActivityMainTestBinding android.databinding.ViewDataBinding

72. DirtyFlag mapping
Dealing with updates
When data is changed, mDirtyFlags is updated
0 0 1
0 1 0
1 0 0
0x1L
0x2L
0x4L
/* flag mapping
flag 0 : vm.authCode
flag 1 : vm
flag 2 : null
flag mapping end*/
ActivityMainBinding.java

73. DirtyFlag mapping
Dealing with updates
When data is changed, mDirtyFlags is updated
0 0 1
0 1 0
1 0 0
0x1L
0x2L
0x4L
/* flag mapping
flag 0 : vm.authCode
flag 1 : vm
flag 2 : initialized
flag mapping end*/
ActivityMainBinding.java

74. /* flag mapping
vm.authCode : 0x1L
vm : 0x2L
initialized : 0x4L
flag mapping end*/
private boolean onChangeVmAuthCode(MutableLiveData<String> VmAuthCode,
int fieldId) {
if (fieldId == BR._all) {
synchronized(this) {
mDirtyFlags |= 0x1L;
}
return true;
}
return false;
ActivityMainBinding.java
mDirtyFlag
vm.authCode : 0x1L

75. /* flag mapping
vm.authCode : 0x1L
vm : 0x2L
initialized : 0x4L
flag mapping end*/
ActivityMainBinding.java
mDirtyFlag
vm : 0x2L
public void setVm(@Nullable com...MainViewModel Vm) {
this.mVm = Vm;
synchronized(this) {
mDirtyFlags |= 0x2L;
}
notifyPropertyChanged(BR.vm);
super.requestRebind();
}

76. /* flag mapping
vm.authCode : 0x1L
vm : 0x2L
initialized : 0x4L
flag mapping end*/
ActivityMainBinding.java
mDirtyFlag
@Override
public void invalidateAll() {
synchronized(this) {
mDirtyFlags = 0x4L;
}
requestRebind();
}
initialized : 0x4L

77. ActivityMainBinding.java
flag initialized : 0x4L
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
val vm = MainViewModel()
val binding = DataBindingUtil.setContentView<ActivityMainBinding>(
this, R.layout.activity_main)
binding.setLifecycleOwner(this)
binding.setVm(viewModel)
}
}
mDirtyFlags = 0x4L

78. ActivityMainBinding.java
flag vm : 0x2L
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
val vm = MainViewModel()
val binding = DataBindingUtil.setContentView<ActivityMainBinding>(
this, R.layout.activity_main)
binding.setLifecycleOwner(this)
binding.setVm(viewModel)
}
}
mDirtyFlags = 0x4L | 0x2L = 0x6L

79. @Override
protected void executeBindings() {
...
dirtyFlags = mDirtyFlags;
if ((dirtyFlags & 0x7L) != 0) {
if ((dirtyFlags & 0x6L) != 0) {
textViewAndroidStringTitleVmYear = textView...getString(R.string.title, vmYear);
}
// read vm.authCode.getValue()
vmAuthCodeGetValue = vmAuthCode.getValue();
// read ValidationUtil.isCodeValid(vm.authCode.getValue())
vmAuthCodeLengthInt6 = ValidationUtil.isCodeValid(vmAuthCodeLength);
}
if ((dirtyFlags & 0x7L) != 0) {
this.button.setEnabled(vmAuthCodeLengthInt6);
TextViewBindingAdapter.setText(this.editText, vmAuthCodeGetValue);
}
if ((dirtyFlags & 0x4L) != 0) {
this.button.setOnClickListener(mCallback1);
TextViewBindingAdapter.setTextWatcher(this.editText, null, null, null,
editTextandroidTextAttrChanged);
}
if ((dirtyFlags & 0x6L) != 0) {
TextViewBindingAdapter.setText(this.textView, textViewAndroidStringTitleVmYear);
}
}
mDirtyFlags = 0x6L

80. @Override
protected void executeBindings() {
...
dirtyFlags = mDirtyFlags;
if ((0x6L & 0x7L) != 0) {
if ((0x6L & 0x6L) != 0) {
textViewAndroidStringTitleVmYear = textView...getString(R.string.title, vmYear);
}
// read vm.authCode.getValue()
vmAuthCodeGetValue = vmAuthCode.getValue();
// read ValidationUtil.isCodeValid(vm.authCode.getValue())
vmAuthCodeLengthInt6 = ValidationUtil.isCodeValid(vmAuthCodeLength);
}
if ((0x6L & 0x7L) != 0) {
this.button.setEnabled(vmAuthCodeLengthInt6);
TextViewBindingAdapter.setText(this.editText, vmAuthCodeGetValue);
}
if ((0x6L & 0x4L) != 0) {
this.button.setOnClickListener(mCallback1);
TextViewBindingAdapter.setTextWatcher(this.editText, null, null, null,
editTextandroidTextAttrChanged);
}
if ((0x6L & 0x6L) != 0) {
TextViewBindingAdapter.setText(this.textView, textViewAndroidStringTitleVmYear);
}
}
mDirtyFlags = 0x6L

81. @Override
protected void executeBindings() {
...
dirtyFlags = mDirtyFlags;
if ((0x6L & 0x7L) != 0) {
if ((0x4L & 0x6L) != 0) {
textViewAndroidStringTitleVmYear = textView...getString(R.string.title, vmYear);
}
// read vm.authCode.getValue()
vmAuthCodeGetValue = vmAuthCode.getValue();
// read ValidationUtil.isCodeValid(vm.authCode.getValue())
vmAuthCodeLengthInt6 = ValidationUtil.isCodeValid(vmAuthCodeLength);
}
if ((0x4L & 0x7L) != 0) {
this.button.setEnabled(vmAuthCodeLengthInt6);
TextViewBindingAdapter.setText(this.editText, vmAuthCodeGetValue);
}
if ((0x4L & 0x4L) != 0) {
this.button.setOnClickListener(mCallback1);
TextViewBindingAdapter.setTextWatcher(this.editText, null, null, null,
editTextandroidTextAttrChanged);
}
if ((0x4L & 0x6L) != 0) {
TextViewBindingAdapter.setText(this.textView, textViewAndroidStringTitleVmYear);
}
}
mDirtyFlags = 0x4L
1 1 0
1 1 1
0x6L
0x7L
(0x6L & 0x7L) != 0
&

82. @Override
protected void executeBindings() {
...
dirtyFlags = mDirtyFlags;
if ((0x6L & 0x7L) != 0) {
if ((0x4L & 0x6L) != 0) {
textViewAndroidStringTitleVmYear = textView...getString(R.string.title, vmYear);
}
// read vm.authCode.getValue()
vmAuthCodeGetValue = vmAuthCode.getValue();
// read ValidationUtil.isCodeValid(vm.authCode.getValue())
vmAuthCodeLengthInt6 = ValidationUtil.isCodeValid(vmAuthCodeLength);
}
if ((0x4L & 0x7L) != 0) {
this.button.setEnabled(vmAuthCodeLengthInt6);
TextViewBindingAdapter.setText(this.editText, vmAuthCodeGetValue);
}
if ((0x4L & 0x4L) != 0) {
this.button.setOnClickListener(mCallback1);
TextViewBindingAdapter.setTextWatcher(this.editText, null, null, null,
editTextandroidTextAttrChanged);
}
if ((0x4L & 0x6L) != 0) {
TextViewBindingAdapter.setText(this.textView, textViewAndroidStringTitleVmYear);
}
}
(0x6L & 0x7L) != 0
mDirtyFlags = 0x4L
1 1 1
0
0x6L
0x7L
&
1 1 0

83. @Override
protected void executeBindings() {
...
dirtyFlags = mDirtyFlags;
if ((0x6L & 0x7L) != 0) {
if ((0x4L & 0x6L) != 0) {
textViewAndroidStringTitleVmYear = textView...getString(R.string.title, vmYear);
}
// read vm.authCode.getValue()
vmAuthCodeGetValue = vmAuthCode.getValue();
// read ValidationUtil.isCodeValid(vm.authCode.getValue())
vmAuthCodeLengthInt6 = ValidationUtil.isCodeValid(vmAuthCodeLength);
}
if ((0x4L & 0x7L) != 0) {
this.button.setEnabled(vmAuthCodeLengthInt6);
TextViewBindingAdapter.setText(this.editText, vmAuthCodeGetValue);
}
if ((0x4L & 0x4L) != 0) {
this.button.setOnClickListener(mCallback1);
TextViewBindingAdapter.setTextWatcher(this.editText, null, null, null,
editTextandroidTextAttrChanged);
}
if ((0x4L & 0x6L) != 0) {
TextViewBindingAdapter.setText(this.textView, textViewAndroidStringTitleVmYear);
}
}
(0x6L & 0x7L) != 0
mDirtyFlags = 0x4L
1 1 1
1 1 0
0x7L
0x6L
&
0x6L 1 1 0

84. @Override
protected void executeBindings() {
...
dirtyFlags = mDirtyFlags;
if ((0x6L & 0x7L) != 0) {
if ((0x4L & 0x6L) != 0) {
textViewAndroidStringTitleVmYear = textView...getString(R.string.title, vmYear);
}
// read vm.authCode.getValue()
vmAuthCodeGetValue = vmAuthCode.getValue();
// read ValidationUtil.isCodeValid(vm.authCode.getValue())
vmAuthCodeLengthInt6 = ValidationUtil.isCodeValid(vmAuthCodeLength);
}
if ((0x4L & 0x7L) != 0) {
this.button.setEnabled(vmAuthCodeLengthInt6);
TextViewBindingAdapter.setText(this.editText, vmAuthCodeGetValue);
}
if ((0x4L & 0x4L) != 0) {
this.button.setOnClickListener(mCallback1);
TextViewBindingAdapter.setTextWatcher(this.editText, null, null, null,
editTextandroidTextAttrChanged);
}
if ((0x4L & 0x6L) != 0) {
TextViewBindingAdapter.setText(this.textView, textViewAndroidStringTitleVmYear);
}
}
(0x6L & 0x7L) != 0
mDirtyFlags = 0x4L
1 1 1
1 1 0
0x7L
0x6L
&
0x6L 1 1 0
!= 0 true

85. @Override
protected void executeBindings() {
...
dirtyFlags = mDirtyFlags;
if (true) {
if (true) {
textViewAndroidStringTitleVmYear = textView...getString(R.string.title, vmYear);
}
// read vm.authCode.getValue()
vmAuthCodeGetValue = vmAuthCode.getValue();
// read ValidationUtil.isCodeValid(vm.authCode.getValue())
vmAuthCodeLengthInt6 = ValidationUtil.isCodeValid(vmAuthCodeLength);
}
if (true) {
this.button.setEnabled(vmAuthCodeLengthInt6);
TextViewBindingAdapter.setText(this.editText, vmAuthCodeGetValue);
}
if (true) {
this.button.setOnClickListener(mCallback1);
TextViewBindingAdapter.setTextWatcher(this.editText, null, null, null,
editTextandroidTextAttrChanged);
}
if (true) {
TextViewBindingAdapter.setText(this.textView, textViewAndroidStringTitleVmYear);
}
}
mDirtyFlags = 0x6L

86. Binding
- Initialized
- set Variables
OK

87. 1
OK
ActivityMainBinding.java
flag vm.authCode : 0x1L
Input 1

88. 1
OK
ActivityMainBinding.java
flag vm.authCode : 0x1L
mDirtyFlags = 0x1L

89. @Override
protected void executeBindings() {
...
dirtyFlags = mDirtyFlags;
if ((0x1L & 0x7L) != 0) {
if ((0x1L & 0x6L) != 0) {
textViewAndroidStringTitleVmYear = textView...getString(R.string.title, vmYear);
}
// read vm.authCode.getValue()
vmAuthCodeGetValue = vmAuthCode.getValue();
// read ValidationUtil.isCodeValid(vm.authCode.getValue())
vmAuthCodeLengthInt6 = ValidationUtil.isCodeValid(vmAuthCodeLength);
}
if ((0x1L & 0x7L) != 0) {
this.button.setEnabled(vmAuthCodeLengthInt6);
TextViewBindingAdapter.setText(this.editText, vmAuthCodeGetValue);
}
if ((0x1L & 0x4L) != 0) {
this.button.setOnClickListener(mCallback1);
TextViewBindingAdapter.setTextWatcher(this.editText, null, null, null,
editTextandroidTextAttrChanged);
}
if ((0x1L & 0x6L) != 0) {
TextViewBindingAdapter.setText(this.textView, textViewAndroidStringTitleVmYear);
}
}
mDirtyFlags = 0x1L

90. @Override
protected void executeBindings() {
...
dirtyFlags = mDirtyFlags;
if (true) {
if (false) {
textViewAndroidStringTitleVmYear = textView...getString(R.string.title, vmYear);
}
// read vm.authCode.getValue()
vmAuthCodeGetValue = vmAuthCode.getValue();
// read ValidationUtil.isCodeValid(vm.authCode.getValue())
vmAuthCodeLengthInt6 = ValidationUtil.isCodeValid(vmAuthCodeLength);
}
if (true) {
this.button.setEnabled(vmAuthCodeLengthInt6);
TextViewBindingAdapter.setText(this.editText, vmAuthCodeGetValue);
}
if (false) {
this.button.setOnClickListener(mCallback1);
TextViewBindingAdapter.setTextWatcher(this.editText, null, null, null,
editTextandroidTextAttrChanged);
}
if (false) {
TextViewBindingAdapter.setText(this.textView, textViewAndroidStringTitleVmYear);
}
}
mDirtyFlags = 0x1L
@Override
protected void executeBindings() {
...
dirtyFlags = mDirtyFlags;
if (true) {
if (false) {
}
// read vm.authCode.getValue()
vmAuthCodeGetValue = vmAuthCode.getValue();
// read ValidationUtil.isCodeValid(vm.authCode.getValue())
vmAuthCodeLengthInt6 = ValidationUtil.isCodeValid(vmAuthCodeLength);
}
if (true) {
this.button.setEnabled(vmAuthCodeLengthInt6);
TextViewBindingAdapter.setText(this.editText, vmAuthCodeGetValue);
}
if (false) {
}
if (false) {
}
}

91. UI Modularization
Seoul

93. Reusable View

94. ItemScheduleinding.java

95. "95
Includes data class SpeakerSchedule(val name: String, val subject: String)
<layout>
<data>
<variable
name="schedule"
type=“com...SpeakerSchedule” />
</data>
<android.support.constraint.ConstraintLayout ...>
<TextView
android:id="@+id/subjectTextView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text=“@{schedule.subject}"/>
<TextView
android:id="@+id/nameTextView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text=“@{schedule.name}" />
...
</android.support.constraint.ConstraintLayout>
</layout>
item_schedule.xml

96. "96
Includes
<layout>
<data>
<variable name="schedule"
type="com...SpeakerSchedule" />
</data>
<android.support.constraint.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
...
<include
android:layout=“@layout/item_schedule”
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:schedule=“@{schedule}” />
...
</android.support.constraint.ConstraintLayout>
</layout>
<include
android:layout=“@layout/item_schedule”
app:schedule=“@{schedule}” />
<variable name="schedule"
type="com...SpeakerSchedule" />

97. Includes
binding.schedule = SpeakerSchedule(“KimKevin”, “Android...”)
<include
android:layout=“@layout/item_schedule”
app:schedule=“@{schedule}” .../>
<variable name="schedule"
type=“com.github.kimkevin…SpeakerSchedule" />

98. Listing & BindingAdapter
@BindingAdapter("schedules")
fun setSchedules(container: LinearLayout,
schedules: List<SpeakerSchedule>) {
container.removeAllViews()
val inflater = container.context.getSystemService(
Context.LAYOUT_INFLATER_SERVICE) as LayoutInflater
schedules.forEach {
val binding = DataBindingUtil.inflate<ItemScheduleBinding>(
inflater, R.layout.item_schedule, container, true)
binding.schedule = it
}
}

99. Listing & BindingAdapter
<LinearLayout
android:orientation="vertical"
app:schedules="@{schedules}" .../>
<variable name="schedules"
type="List&lt;SpeakerSchedule&gt;" />
val schedules = mutableListOf<SpeakerSchedule>().apply {
add(SpeakerSchedule("Kevin", "Android"))
add(SpeakerSchedule("David", “Data Binding”))
}
binding.schedule = schedules

100. "100
Listing & ViewHolder

101. Listing & ViewHolder
ItemViewHolder
class ItemViewHolder(v: View) : RecyclerView.ViewHolder

102. Listing & ViewHolder
HeaderViewHolder
ItemViewHolder
class ItemViewHolder(v: View) : RecyclerView.ViewHolder
class HeaderViewHolder(v: View) : RecyclerView.ViewHolder

103. Listing & ViewHolder
HeaderViewHolder
ItemViewHolder
ProgressViewHolder
class ItemViewHolder(v: View) : RecyclerView.ViewHolder
class HeaderViewHolder(v: View) : RecyclerView.ViewHolder
class ProgressViewHolder(v: View) : RecyclerView.ViewHolder

104. class BindingViewHolder<T: ViewDataBinding>
constructor(val binding: T): RecyclerView.ViewHolder(binding.root)

105. class BindingViewHolder<T: ViewDataBinding>
constructor(val binding: T): RecyclerView.ViewHolder(binding.root)
override fun onCreateViewHolder(parent: ViewGroup, position: Int):
BindingViewHolder<ViewDataBinding> {
return BindingViewHolder(ItemScheduleBinding.inflate(
LayoutInflater.from(parent.context), parent, false))
}
override fun onBindViewHolder(
viewHolder: BindingViewHolder<ViewDataBinding>, position: Int) {
val binding = viewHolder.binding as ItemScheduleBinding
binding.schedule = items.get(position)
}
Adapter

106. Unit Testing
Seoul

107. TextView
Welcome message
for Devfest Seoul of the year
Requirements
EditText
6 numbers for authentication Button
Enabled for login
with 6 numbers

108. TextView
Welcome message
for Devfest Seoul of the year
Requirements
EditText
6 numbers for authentication Button
Enabled for login
with 6 numbers
Business
UI

109. <TextView
android:text=“@{@string/title(vm.year)}”
.../>

110. ???
<TextView
android:text=“@{@string/title(vm.year)}”
.../>
Business
UI

111. ???
<TextView
android:text=“@{@string/title(vm.year)}”
.../>
Business
UI
vm.year

112. <TextView
android:text=“@{@string/title(vm.year)}”
.../>
Business
UI
@Test
fun initVm_setYear() {
vm = MainViewModel()
assertTrue(vm.year, deafest.year)
}
val devfest = repository.getDevfest()
vm.year = devfest.year
MainViewModel

113. <Button
android:enabled=“@{vm.authCode >= 6}”
.../>

114. Business
UI
<Button
android:enabled=“@{vm.authCode >= 6}”
.../>

115. ???
<Button
android:enabled=“@{vm.authCode >= 6}”
.../>
Business
UI

116. vm.authCode >= 6
<Button
android:enabled=“@{vm.authCode >= 6}”
.../>
Business
UI

117. fun String?.isCodeValid()
= this?.length ?: 0 >= 6
<Button
android:enabled=“@{ValidationUtil.isCodeValid(vm.authCode)}”
.../>
Business
UI

118. <Button
android:enabled=“@{ValidationUtil.isCodeValid(vm.authCode)}”
.../>
@Test
fun validateLessThan6Numbers() {
assertFalse(“1234".isCodeValid())
}
Business
UI

119. <Button
android:enabled=“@{ValidationUtil.isCodeValid(vm.authCode)}”
.../>
@Test
fun validate6Numbers() {
assertTrue("123456".isCodeValid())
}
Business
UI

120. Seoul
Thank you
Yongjun Kim, kakaobank
@imkimkevin

121. Q&A
imkimkevin@gmail.com
https://www.facebook.com/imkimkevin
Busan