Data Binding in Android

Transcript

1. Data Binding in Android Ihor Dzikovskyy GDG Ternopil
2. What is Data Binding Data Binding is a technique that allows us to connect our Ui elements and a data model
3. Data Binding in Android • Introduced in Android Marshmallow • The Data Binding Library is a support library (can be used with Android API level 7+) • Android Plugin for Gradle 1.5.0-alpha1 or higher is required • Android Studio 1.3 and later provides support for data binding
4. Getting Ready • Download the support repository using the SDK manager • Add the dataBinding element to your app build.gradle file, as shown in the snippet below
5. Layout XML Without Data Binding
6. Java code Without Data Binding
7. Data Binding Layout
8. Data Binding in Activity
9. Data Binding in Activity ActivityMainBinding binding = ActivityMainBinding.inflate(getLayoutInflater()); setContentView(binding.getRoot()); Data Binding inside a ListView or RecyclerView adapter ListItemBinding binding = ListItemBinding.inflate(layoutInflater, viewGroup, false); //or ListItemBinding binding = DataBindingUtil.inflate(layoutInflater, R.layout.list_item, viewGroup, false);
10. Data Binding in Fragment
11. No More findViewById Basic UI logic From Java To XML Layout
12. No More findViewById
13. <include> tag
14. How it works? All code generation and expression parsing happens at compile time => if an expression has error the project won't compile No reflection, no runtime overhead
15. Events, Method References, Callbacks
16. Events, Method References
17. Events, Method References
18. Events, Listener Objects
19. Events, Listener Objects
20. Listener Bindings Binding expressions that run when an event happens Similar to method references, but they let you run arbitrary data binding expressions. Available with Android Gradle Plugin for Gradle version 2.0 and later Only your return value must match the expected return value of the listener (unless it is expecting void)
21. Listener Bindings Listeners are represented by lambda expressions public class Presenter { public void onSaveClick(Task task){} } android:onClick="@{() -> presenter.onSaveClick(task)}"
22. Listener Bindings You can either ignore all parameters to the method or name all of them public class Presenter { public void onSaveClick(View view, Task task){} } android:onClick="@{(v) -> presenter.onSaveClick(v, task)}"
23. Listener Bindings You can either ignore all parameters to the method or name all of them public class Presenter { public void completeChanged(Task task, boolean completed){} } <CheckBox android:layout_width="wrap_content" android:layout_height="wrap_content" android:onCheckedChanged="@{(cb, isChecked) -> presenter.completeChanged(task, isChecked)}" />
24. Listener Bindings Your expressions must return the same type of value as well public class Presenter { public boolean onLongClick(View view, Task task){} } android:onLongClick="@{(view) -> presenter.onLongClick(view, task)}"
25. Imports <data> <import type="android.view.View"/> <variable name="user" type="com.example.User"/> </data> <TextView android:text="@{user.lastName}" android:layout_width="wrap_content" android:layout_height="wrap_content" android:visibility="@{user.isAdult ? View.VISIBLE : View.GONE}"/>
26. Imports, alias <data> <import type="android.view.View" alias="v1"/> <import type="com.example.View" alias="v2"/> <variable name="user" type="com.example.User"/> </data> <TextView android:text="@{user.lastName}" android:layout_width="wrap_content" android:layout_height="wrap_content" android:visibility="@{user.isAdult ? v1.VISIBLE : v1.GONE}"/>
27. Custom Binding Class Names <data class="BindingMain"> <variable name="user" type="com.example.User"/> </data>
28. Expression Language • Mathematical + - / * % • String concatenation + • Logical && || • Binary & | ^ • Unary + - ! ~ • Shift >> >>> << • Comparison == > < >= <= • instanceof • Grouping () • Literals - character, String, numeric, null • Cast • Method calls • Field access • Array access [] • Ternary operator ?:
29. Missing Operations • this • super • new
30. Expression Examples android:text="@{String.valueOf(index + 1)}" android:visibility="@{age < 13 ? View.GONE : View.VISIBLE}" android:transitionName='@{"image_" + id}'
31. Null Coalescing Operator android:text="@{user.name ?? user.lastName}" android:text="@{user.name != null ? user.name : user.lastName}" =
32. Resources android:padding="@{large? @dimen/largePadding : @dimen/smallPadding}" android:text="@{@string/nameFormat(firstName, lastName)}" android:text="@{@plurals/banana(bananaCount)}
33. Observable Objects public class User extends BaseObservable { private String name; @Bindable public String getName() { return name; } public void setName(String name) { this.name = name; notifyPropertyChanged(BR.name); } }
34. ObservableFields private static class User { public final ObservableField<String> firstName = new ObservableField<>(); public final ObservableField<String> lastName = new ObservableField<>(); public final ObservableInt age = new ObservableInt(); } user.firstName.set("John"); int age = user.age.get();
35. Two way binding <EditText android:text="@{user.firstName}" /> <EditText android:text="@={user.firstName}" />
36. View Attributes <CheckBox android:id="@+id/showName" android:layout_width="wrap_content" android:layout_height="wrap_content"/> <TextView android:text="@{user.firstName}" android:layout_width="wrap_content" android:layout_height="wrap_content" android:visibility="@{showName.checked ? View.VISIBLE : View.GONE}"
37. Custom attributes,BindingAdapter <ImageView app:imageUrl="@{user.pictureUrl}" /> @BindingAdapter("bind:imageUrl") public static void loadImage(ImageView view, String imageUrl) { Picasso.with(view.getContext()) .load(imageUrl) .into(view); }
38. Custom attributes, BindingAdapter <ImageView android:src="@{user.pictureUrl}" /> @BindingAdapter("android:src") public static void loadImage(ImageView view, String imageUrl) { Picasso.with(view.getContext()) .load(imageUrl) .into(view); }
39. BindingAdapter, BindingAdapter @BindingAdapter({"android:src", "app:error"}) public static void loadImage(ImageView view, String url, Drawable error) { Picasso.with(view.getContext()) .load(url) .error(error) .into(view); }
40. Working with RecyclerView public class MyViewHolder extends RecyclerView.ViewHolder { private final ItemBinding binding; public MyViewHolder(ItemBinding binding) { super(binding.getRoot()); this.binding = binding; } public void bind(Item item) { binding.setItem(item); binding.executePendingBindings(); } }
41. Working with RecyclerView public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { LayoutInflater layoutInflater = LayoutInflater.from(parent.getContext()); ItemBinding itemBinding = ItemBinding.inflate(layoutInflater, parent, false); return new MyViewHolder(itemBinding); } public void onBindViewHolder(MyViewHolder holder, int position) { Item item = getItemForPosition(position); holder.bind(item); }
42. Working with RecyclerView executePendingBindings() - forces the bindings to run immediately instead of delaying them until the next frame
43. Reusing the ViewHolder public class MyViewHolder extends RecyclerView.ViewHolder { private final ViewDataBinding binding; public MyViewHolder(ViewDataBinding binding) { super(binding.getRoot()); this.binding = binding; } public void bind(Object obj) { binding.setVariable(BR.obj, obj); binding.executePendingBindings(); } } <variable name="obj" type="Item"/>
44. Pros and Cons + • Eliminates much boilerplate • Powerful, easy to implement custom attributes • Compile time validation • Performance - faster than findViewById • Reusable methods and adapters - • Presentation logic on the layout • Harder to debug • The auto-generated .class increases app size • IDE integration • Refactoring
45. Thanks! Any questions? DataBinding in Android: goo.gl/8qYvnc