android

Data Binding

Posted by アライさん on 2019年11月12日

data binding xml中无须做null判断，自带

module的build.gradle

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android {
    dataBinding {
       enabled true
    }
}

xml

自动创建：在xml文件的根节点点击，就会出现灯泡，点击灯泡可选“Convert to data binding layout”
手动创建： 

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<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">
    <data>
        <variable
            name="viewmodel"
            type="io.github.araisann.navigationtest.WordViewModel" />
    </data>
    <!--界面布局部分-->
</layout>

xml中调用： 

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android:text="@{@string/fragment0 + viewmodel.allWords.size()}"
android:onClick="@{(v) -> viewmodel.jumpFragment2(v)}"

Fragment

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class Fragment0 : Fragment() {
    lateinit var wordViewModel: WordViewModel

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        wordViewModel = ViewModelProviders.of(activity!!).get(WordViewModel::class.java)
    }

    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        val fragmentTodayBinding = DataBindingUtil.inflate(
            inflater,
            R.layout.fragment0,
            container,
            false
        ) as Fragment0Binding

        val view = fragmentTodayBinding.root
        fragmentTodayBinding.viewmodel = wordViewModel
        return view
    }

}

ViewModel

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class WordViewModel : ViewModel() {
    val allWords: MutableLiveData<List<Word>>

    init {
        val list = ArrayList<Word>()
        list.add(Word("DEFAULT"))
        list.add(Word("DEFAULT"))
        list.add(Word("DEFAULT"))
        list.add(Word("DEFAULT"))
        allWords = MutableLiveData()
        allWords.value = list
    }

    fun modify(position: Int, wordStr: String) {
        if (position > allWords.value?.size ?: 0 || position < 0 ){
            return
        }
        allWords.value?.let {
            it[position].word = wordStr
        }
    }

    fun jumpFragment2(v:View){
        //用Navigation的方式跳转到新Fragment
        val action = Fragment0Directions.actionFragment0ToFragment1("time", 1)
        Navigation.findNavController(v).navigate(action)
    }
}

Adapter使用Data Binding

点击事件依旧通过手动设置
item: 

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<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android">
    <data>
        <variable
            name="word"
            type="io.github.araisann.navigationtest.Word" />
    </data>
    <!--界面布局-->
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@{word.word}" />
    </LinearLayout>
</layout>

adapter: 

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class MyRecyclerAdapter(private val allWords: List<Word>?) :
    RecyclerView.Adapter<MyRecyclerAdapter.MyViewHolder>() {
    var listener: OnItemClickListener? = null

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
        val layoutInflater = LayoutInflater.from(parent.context)
        val itemBinding = ItemWordBinding.inflate(layoutInflater, parent, false)
        return MyViewHolder(itemBinding)
    }

    override fun getItemCount(): Int {
        return allWords?.size ?: 0
    }

    override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
        allWords?.let {
            holder.bind(it[position])
        }
        holder.binding.itemRoot.setOnClickListener { view ->
            //点击事件
            allWords?.let {
                listener?.onClick(view, allWords[position])
            }
        }
    }

    fun setOnItemClickListener(listener: OnItemClickListener) {
        this.listener = listener
    }

    interface OnItemClickListener {
        fun onClick(view: View, data: Word)
    }

    //ViewHolder
    class MyViewHolder(val binding: ItemWordBinding) :
        RecyclerView.ViewHolder(binding.root) {
        fun bind(word: Word) {
            binding.word = word
            binding.executePendingBindings()
        }
    }
}

Fragment: 

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class Fragment0 : Fragment() {
    private lateinit var wordViewModel: WordViewModel
    private lateinit var fragment0Binding: Fragment0Binding
    private lateinit var adapter: MyRecyclerAdapter

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        wordViewModel = ViewModelProviders.of(activity!!).get(WordViewModel::class.java)
    }
    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
         fragment0Binding = DataBindingUtil.inflate(
            inflater,
            R.layout.fragment0,
            container,
            false
        ) as Fragment0Binding
        fragment0Binding.viewmodel = wordViewModel
        setupRecyclerView()
        return fragment0Binding.root
    }
    private fun setupRecyclerView(){
       val recyclerView =  fragment0Binding.recyclerView
        recyclerView.layoutManager = LinearLayoutManager(context)
        adapter = MyRecyclerAdapter(wordViewModel.allWords.value)
        adapter.setOnItemClickListener(object : MyRecyclerAdapter.OnItemClickListener{
            override fun onClick(view: View, data: Word) {
            }
        })
        recyclerView.adapter = adapter
    }
}

相关注解

@BindAdapter(‘name’):自定义方法

给View增加一个自定义的属性，并绑定。
不推荐覆盖系统自带的属性。
可以参考ImageViewBindingAdapter等自带实现，里面的”android:src”等自带属性也是通过@BindingAdapter实现的。 

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<data>
  <variable 
      name="myValue"
      type="xx.xx.xx.A"/>
</data>
<MyView 
  app:myAttribute="@{myValue}"
/>
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//Adapter中
@BindingAdapter("myAttribute")
@JvmStatic
fun setMyAttribute(view: MyView, value: xx.xx.xx.A) {
}

@BindingMethod、 @BindingMethods

可以参考ImageViewBindingAdapter等自带实现。
类似简单版@BindAdapter。通过给类增加注释，实现xml属性和方法的bind。直接set。 

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@BindingMethods({
  BindingMethod(type = MyView::class, attribute = "myAttribute", method = "setMyAttribute"),
  BindingMethod(type = MyView::class, attribute = "myAttribute2", method = "setMyAttribute2")
})

@Bindable

绑定，实现通知UI更新。
不过有LiveData了，似乎不太需要这个了。
DataBinding调用setLifecycleOwner，xml即可随着数据改变而改变。




Tags
android