databinding

layout expression of the language

https://codelabs.developers.google.com/codelabs/android-databinding/#0

https://developer.android.com/topic/libraries/data-binding

Create first layout expression

1. when you want to use it in your own projects the first step is to enable the library in the modules that will use it:

android {
...
    dataBinding {
       enabled true
    }
}

2. Convert to data binding layout

   打开布局文件，选中根布局的 ViewGroup，按住 option + 回车键，点击 “Convert to data binding layout”，就可以生成 DataBinding 需要的布局规则

<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="name"  //不能用下划线 "_"
            type="String"/>

        <variable
            name="lastName"
            type="String"/>
    </data>

    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <TextView
            android:id="@+id/plain_name"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginStart="16dp"
            android:layout_marginTop="8dp"
            android:layout_marginEnd="128dp"
            android:text="@{name}"			
            android:textAppearance="@style/TextAppearance.AppCompat.Large"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/name_label"/>

        <TextView
            android:id="@+id/plain_lastname"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginStart="16dp"
            android:layout_marginTop="8dp"
            android:layout_marginEnd="128dp"
            android:text="@{lastName}"
            android:textAppearance="@style/TextAppearance.AppCompat.Large"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/lastname_label"/>
            
       </androidx.constraintlayout.widget.ConstraintLayout>    
   </layout>

3. Bind TextView

class PlainOldActivitySolution2 : AppCompatActivity() {

    // Obtain ViewModel from ViewModelProviders
    private val viewModel by lazy { ViewModelProviders.of(this).get(SimpleViewModel::class.java) }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        val binding: PlainActivitySolution2Binding =
            DataBindingUtil.setContentView(this, R.layout.plain_activity_solution_2)

        binding.name = "John"
        binding.lastName = "lice"

        // TODO: Explicitly setting initial values is a bad pattern. We'll fix that later on.
        updateLikes()
    }
}
}

Dealing with user events Observering data

<data>
     <variable
             name="viewmodel"
             type="com.example.android.databinding.basicsample.data.SimpleViewModel"/>
 </data>

android:onClick="@{() -> viewmodel.onLike()}"
   
binding.viewmodel = viewModel

private val _likes =  MutableLiveData(0)
 fun onLike() {
       _likes.value = (_likes.value ?: 0) + 1
 }

<TextView
            android:id="@+id/likes"
            android:text="@{Integer.toString(viewmodel.likes)}"

Using Binding Adapters

1. One parameter

@BindingAdapter("android:text")
  public static void setText(TextView view, CharSequence text) {
      // Some checks removed for clarity

      view.setText(text);
  }

@BindingAdapter("app:hideIfZero")
 fun hideIfZero(view: View, number: Int) {
     view.visibility = if (number == 0) View.GONE else View.VISIBLE
 }

<ProgressBar
            android:id="@+id/progressBar"
            app:hideIfZero="@{viewmodel.likes}"

2. Create a Binding Adapter with multiple parameters

   <ProgressBar
                  android:id="@+id/progressBar"
                  app:hideIfZero="@{viewmodel.likes}"
                  app:progressScaled="@{viewmodel.likes}"
                  android:max="@{100}"

oberver class field

https://developer.android.com/topic/libraries/data-binding/observability#observable_fields

https://developer.android.com/topic/libraries/data-binding/observability#observable_objects

Using Binding Adapters to create custom attributes

@BindingAdapter(value=["app:setSleepData"])
fun setSleepData(viewBodySleep: ViewBodySleep, sleepData: String) {
    viewBodySleep.setSleepData(sleepData)
}

<com.android.util.view.ViewBodySleep
    android:id="@+id/view_body_sleep"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:paddingLeft="55dp"
    android:paddingRight="48dp"
    app:setSleepData="@{vmBodyFragment.spData}"
    app:layout_constraintTop_toTopOf="parent" />

https://developer.android.com/topic/libraries/data-binding/expressions#expression_language

Work with observable data objects

• isNull

  android:text='@{viewModel.patientInfo.remoteCheckReceiveName??""}'

• visible

  @BindingAdapter("app:goneUnless")
  fun goneUnless(view: View, visible: Boolean) {
      view.visibility = if (visible) View.VISIBLE else View.GONE
  }

android-databinding

https://mp.weixin.qq.com/s?__biz=MzAwODY4OTk2Mg==&mid=2652046992&idx=1&sn=b8b4c47537be1227eecd01c1eaee2550&chksm=808ca6d5b7fb2fc32d9ec361c91a2958e51a2db1c6b20370e7ef6493bb5cb20314cda6ab059c&scene=38#wechat_redirect

https://juejin.im/post/5d2be05ff265da1bd605d49a

https://mp.weixin.qq.com/s/4UP-pDs0FK66g1QUQvRN6A

定义xml背景

https://juejin.im/post/5b95c6a0e51d450e664b0aa0

https://www.jianshu.com/p/741103ba2ff1

https://www.cs.usfca.edu/~galles/visualization/RedBlack.html