以spinner举例，首先定义一个在model
object SPModel : BaseObservable(){
var pos = false
@Bindable
get(){
return field
}
set(value){
field = value
notifyPropertyChanged(BR.pos)
}
}
pos即spinner的selected position
然后给用BindingAdapter给spinner赋值
@JvmStatic
@BindingAdapter("selectedPos")
fun setSelectedPos(sp:Spinner,pos:Int){
sp.setSelection(pos)
}
这个时候，当我们修改model的pos的值的时候，spinner的选中项就会变成对应position的项
然后需要对spinner进行反向绑定，即用 Databinding对onItemSelectedListener进行监听
@JvmStatic
@InverseBindingAdapter(attribute = "selectedPos",event = "posAttrChanged")
fun getSelectedPos(sp:Spinner){
return sp.selectedItemPosition
}
@JvmStatic
@BindingAdapter("posAttrChanged")
fun setSPChanged(sp:Spinner,lis:InverseBindingListener){
sp.onItemSelectedListener = object : AdapterView.OnItemSelectedListener {
override fun onItemSelected(parent: AdapterView<*>?, view: View?, position: Int, id: Long) {
lis.onChange()
}
override fun onNothingSelected(parent: AdapterView<*>?) { }
}
}
这个BindingAdapter对应的即是InverseBindingAdapter中的event，所以value需要与InverseBindingAdapter中的event一致
最后则是xml中添加属性，根目录添加 xmlns:bind="http://schemas.android.com/tools"
xmlns:bind="http://schemas.android.com/tools"
<Spinner
android:layout_width = "300dp"
android:layout_width = "60dp"
android:entries = "@array/test"
bind:selectedPos = "@={model.pos}"
/>
