2.9 overview of databinding knowledge points

There may only be one right , There are thousands of mistakes .

One 、 Basic usage

1. Enable dataBinding

// stay module Of build.gradle in 
apply plugin: 'kotlin-kapt'// must 
android{
  //AS 4.0  following ,
  dataBinding{
    enabled true
  }
  //AS 4.1 after 
  bindingFeature{
        dataBinding = true
        // for view binding :
        // viewBinding = true
  }
}

1. UI reform

<layout>
    <data class="">
    
  </data>
  <!--  The original UI Of xml Layout in layout Just inside the label .data Label memory for xml Data variables for , type  -->
  <LinearLayout>
  
  </LinearLayout>
  
</layout>

1. viewBinding and dataBinding

2. xml Data types in

   variable Declare variables ;import Import type ; about xml Special symbols of need escape similar &

   binding xml And data Format ：@{}、@={}( Two way binding )

   • Available expressions 、 Function call 、 Property parameters

   • ?? Sentenced to empty

   • ?: Ternary operator

   • @string/str_name Resource Citation , Available placeholders format

   • + Concatenate characters , Use `` The quotation marks

   • default Set the default value

   • include binding

   • Click event

   οnclick="@{()->vm.click()}"
   οnclick="@{(v)->vm.click(v)}"
   οnclick="@{()->vm.click(context)}"
   οnclick="@{BindHelp::staticClick}"
   οnclick="@{callback}"

   • EditText Two-way binding of text="@={etStr}"

   • UI Middle Association xml Of dataBinding

   //activity in 
   val binding =
               DataBindingUtil.setContentView<ActivityBaseUseBinding>(this, R.layout.activity_base_use)
   //fragment in  xxxBinding.inflater()

Two 、 Advanced usage

1. android:onCheckedChanged="@{(switch,checked)->vm.broadcast(checked)}"

2. Binding Respond to UI Of data Bean

3. Adapter Adapter for list ,include

4. @BindingConversion Transformation support

5. @BindingAdapter Advanced support

6. @InverseBindingAdapter Inverse binding

   1. @bindingadapter（xxx）

   2. @bindingadapter（xxxAttrChanged）

   3. @inverseBindingadapter

7. @BindingMethods Adaptation extension support binding Function of

Experience of pit ：

1. TextView Of text attribute , Have its attention data Not for Number type

2. xml Chinese characters cannot be Chinese

3. Reflection attribute 、 The function must be public

4. Use liveData As dataBinding When , Bear in mind ui Set in binding.lifecycleOwner

5. observableField Data time , Some occasions require initialization , Otherwise, an error is reported during operation , It's not easy to check

6. IDE Development to avoid character collapse caused by Chinese input method , especially xml in .

7. ./gradlew app:build,./gradlew app:dependencies etc. gradle The instructions of are often , It's easy to make mistakes

   --stacktrace --debug And other necessary parameters , Use Execution failed for task Build error messages .

8. clean,rebuild,clear cache,delete build and apk Folder

9. build.gradle,--offline,AS&gradle Version match for