Jetpack series (8) - Data Binding && View Binding

Jetpack series (8) – Data Binding && View Binding

A brief introduction to Hilt

First impression

Data Binding, including all View Binding functions, support bidirectional Binding

View Binding only supports Binding views, an alternative to the Kotlin-Android-Extensions plugin

Data Binding and View Binding can exist together

Data Binding performance is inferior to View Binding, so some projects only use View Binding

The basic concept

I’m just going to use a View Binding instead of findViewById(), Data Binding

The basic use

View Binding basic use

willviewBindingElement to whichbuild.gradleIn the file

android {
    ...
    viewBinding {
        enabled = true}}Copy the code

Use view bindings in your Activity

In the ActivityonCreate()Method to call the static contained in the generated binding classinflate()methods
withBinding. The control IdOperating controls

// MainActivity
class MainActivity : AppCompatActivity() {
    private lateinit var binding: ActivityMainBinding
    
    override fun onCreate(savedInstanceState: Bundle?). {
        super.onCreate(savedInstanceState)
        // Automatically generated
        binding = ActivityMainBinding.inflate(layoutInflater)
        setContentView(binding.root)
    }    
}
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Use view binding in fragments

Please in fragmentsonCreateView()Method, calling the static contained in the generated binding classinflate()methods

class DeepLinkFragment : Fragment() {

    private var _binding: FragmentDeepLinkBinding? = null
    private val binding
        get() = _binding!!

    private val mainViewModel: MainViewModel by activityViewModels()

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup? , savedInstanceState:Bundle?).: View {
        _binding = FragmentDeepLinkBinding.inflate(inflater, container, false)
        return binding.root
    }
 
    override fun onDestroy(a) {
        super.onDestroy()
        _binding = null}}Copy the code

Use ViewBinding in Adapter

By binding classesinflateMethods the incomingViewHolder

// WordListAdapter.kt
class WordListAdapter : ListAdapter<Word, WordViewHolder>(WORDS_COMPARATOR) {

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): WordViewHolder =
        WordViewHolder.create(parent)

    override fun onBindViewHolder(holder: WordViewHolder, position: Int) {
        val item = getItem(position)
        holder.bind(item)
    }

    companion object {
        private val WORDS_COMPARATOR = object : DiffUtil.ItemCallback<Word>() {
            override fun areItemsTheSame(oldItem: Word, newItem: Word): Boolean =
                oldItem == newItem

            override fun areContentsTheSame(oldItem: Word, newItem: Word): Boolean =
                oldItem.word == newItem.word

        }
    }

}

class WordViewHolder(binding: ItemWordBinding) : RecyclerView.ViewHolder(binding.root) {

    private val textView: TextView = binding.textView

    fun bind(word: Word?).{ textView.text = word? .word? :""
    }

    companion object {
        fun create(parent: ViewGroup): WordViewHolder {
            val binding =
                ItemWordBinding.inflate(LayoutInflater.from(parent.context), parent, false)
            return WordViewHolder(binding)
        }
    }
}
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Data Binding basic use

Modify the build.gradle file

dataBinding {
    enabled = true
}
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Generate the data Binding layout, see Point 3

I’m going to do a refresh effect here
Click on the eventonClick="@{()-> model.updateTaps()}"


        
<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools">

    <data>
        <variable
            name="model"
            type="com.huang.myapplication.viewmodel.MainViewModel" />
    </data>

    <androidx.constraintlayout.widget.ConstraintLayout
        android:id="@+id/home_contain"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".ui.main.home.HomeFragment">
 
        <Button
            android:id="@+id/btn_add"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:layout_marginStart="10dp"
            android:layout_marginTop="10dp"
            android:layout_marginEnd="10dp"
            android:text="@string/refresh"
            android:onClick="@{()-> model.updateTaps()}"
            app:layout_constraintHorizontal_weight="1"
            app:layout_constraintLeft_toRightOf="@+id/btn_next"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

        <TextView
            android:id="@+id/tv_count"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginStart="10dp"
            android:text="@{model.taps}"
            app:layout_constraintBottom_toBottomOf="@+id/tv_current_count"
            app:layout_constraintLeft_toRightOf="@+id/tv_current_count"
            app:layout_constraintTop_toTopOf="@+id/tv_current_count" />

 
    </androidx.constraintlayout.widget.ConstraintLayout>
</layout>
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Look at the data in the viewModel

class MainViewModel @Inject constructor(
    private val repository: WordRepository
) : ViewModel() {

    private var _tapCount = 0
    private var _taps = MutableLiveData<String>("$_tapCount taps")
   
    val taps: LiveData<String> =  _taps

    fun updateTaps(a) {
        _tapCount++
        _taps.value = "$_tapCount taps"}}Copy the code

Binding view

The Activity generates the Binding view class

 // Method 1:
 val binding: ActivityXxxBinding = DataBindingUtil.setContentView(
     this, R.layout.activity_main)

 // Method 2:
 val binding: ActivityXxxBinding = ActivityMainBinding.inflate(getLayoutInflater())
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Use data binding items in Fragment, ListView, or RecyclerView adapters

// Method 1:
val listItemBinding = ListItemBinding.inflate(layoutInflater, viewGroup, false)

// Method 2:
val listItemBinding = DataBindingUtil.inflate(layoutInflater,R.layout.list_item, viewGroup, false)
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You can use LiveData objects as data binding sources to automatically notify the interface of data changes, requiring binding.lifecycleOwner = this to set the lifecycle of the view-binding class

class HomeFragment : Fragment() {

    private var _binding: FragmentHomeBinding? = null
    private val binding
        get() = _binding!!

    private lateinit var adapter: WordListAdapter

    private val mainViewModel: MainViewModel by activityViewModels()

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup? , savedInstanceState:Bundle?).: View {
        _binding = DataBindingUtil.inflate(layoutInflater, R.layout.fragment_home,container, false)
        setHasOptionsMenu(true)
        binding.lifecycleOwner = this
        return binding.root
    }

    override fun onDestroy(a) {
        super.onDestroy()
        _binding = null}}Copy the code

Related knowledge points

ViewBinding ignores files

Once ViewBinding is enabled, Android Studio automatically generates a Binding class for each layout file we write
The Binding class is named after the layout file is humped and ends with a Binding.
If there are layout files for which you do not want to generate a Binding class, you can add tools at the root of the layout file :viewBindingIgnore=”true”
```
<LinearLayout
    .
    tools:viewBindingIgnore="true" >.</LinearLayout>
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```

Include layout in a View Binding

The View Binding uses an include to add an ID, which is searched by id

<include
         android:id="@+id/includeTitle"
         layout="@layout/include_title" />/ / InOutFragment kt binding. IncludeTitle. ToolbarTitle. Text = "in operation"Copy the code

Quickly generate a Data Binding layout

alt + Enterchoosecover data to data binding layout

Binding expressions (Data Bindng)

Arithmetic operator+ - / * %
String concatenation operator+
Logical operator&& | |
Binary operator& | ^
Unary operator+ -! ~
Shift operator>> >>> <<
Comparison operator== > < >= <=(Please note that<Need to escape as<)
instanceof
Grouping operator(a)
Literal operators – characters, strings, numbers,null
Type conversion
The method call
Field access
Array access[]
Ternary operator? :

Data Binding

@ = {}The notation, which importantly contains the “=” symbol, receives data changes for attributes and listens for user updates at the same time

A link to the

Jetpack (1) – Navigation

Jetpack series (Ii) — Lifecycle

Jetpack series (3) – LiveData

Jetpack series (4) – ViewModel

Jetpack series (5) — Room

Jetpack series (6) – Paging3

Jetpack (7) – Hilt

The resources

A website

Website 2

Jetpack series (8) – Data Binding && View Binding