我们正在研究的项目使用MVVM体系结构，房间和2路数据绑定。在我的layout.xml文件中，我们使用AutoCompleteTextView作为国家/地区选择器。国家是我们项目中的模型：
以下是代码，但是很显然，我无法发布整个项目，因此，如果您需要更多数据，请告诉我。
Country.java
@Entity
public class Country
{
@PrimaryKey
@ColumnInfo(name = "ID")
private Long id;
@ColumnInfo(name = "Name")
private String countryName;
@ColumnInfo(name = "Code")
private String countryCode;
public Long getId()
{
return id;
}
public void setId(Long id)
{
this.id = id;
}
public String getCountryName()
{
return countryName;
}
public void setCountryName(String countryName)
{
this.countryName = countryName;
}
public String getCountryCode()
{
return countryCode;
}
public void setCountryCode(String countryCode)
{
this.countryCode = countryCode;
}
}
layout.xml
<?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>
<import type="android.view.View" />
<variable name="myViewModel" type="ViewModel" />
</data>
<android.support.v4.widget.NestedScrollView>
<AutoCompleteTextView
android:id="@+id/countryAutoCompleteTextView"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:completionThreshold="1"
android:dropDownWidth="match_parent"
android:imeOptions="actionNext"
android:inputType="text"
android:maxLines="1"
android:text="@={myViewModel.countryObservable}"
android:textIsSelectable="false"
android:textColor="@color/edit_text_black_color_selector" />
<android.support.v4.widget.NestedScrollView>
</layout>
View.java
public class View {
onCreate(){
ViewModel myViewModel = new ViewModel();
ActivityViewBinding binding = DataBindingUtil();
binding.setViewModel(myViewModel);
AutoCompleteCountryAdapter countryAdapter = new AutoCompleteAdapter();
binding.countryAutoCompleteTextView.setAdapter(countryAdapter);
}
}
ViewModel.java
public class ViewModel extends AndroidViewModel {
private final ObservableField<String> countryObservable = new ObservableField<>();
}
AutoCompleteCountryAdapter.java我从here
复制了代码public class AutoCompleteCountryAdapter extends ArrayAdapter<CountryItem> {
private List<CountryItem> countryListFull;
public AutoCompleteCountryAdapter(@NonNull Context context, @NonNull List<CountryItem> countryList) {
super(context, 0, countryList);
countryListFull = new ArrayList<>(countryList);
}
@NonNull
@Override
public Filter getFilter() {
return countryFilter;
}
@NonNull
@Override
public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
if (convertView == null) {
convertView = LayoutInflater.from(getContext()).inflate(android.R.layout.simple_dropdown_item_1line, parent, false);
}
TextView textViewName = convertView.findViewById(R.id.text_view_name);
CountryItem countryItem = getItem(position);
if (countryItem != null) {
textViewName.setText(country.getCountryName());
}
return convertView;
}
private Filter countryFilter = new Filter() {
@Override
protected FilterResults performFiltering(CharSequence constraint) {
FilterResults results = new FilterResults();
List<CountryItem> suggestions = new ArrayList<>();
if (constraint == null || constraint.length() == 0) {
suggestions.addAll(countryListFull);
} else {
String filterPattern = constraint.toString().toLowerCase().trim();
for (CountryItem item : countryListFull) {
if (item.getCountryName().toLowerCase().contains(filterPattern)) {
suggestions.add(item);
}
}
}
results.values = suggestions;
results.count = suggestions.size();
return results;
}
@Override
protected void publishResults(CharSequence constraint, FilterResults results) {
clear();
addAll((List) results.values);
notifyDataSetChanged();
}
@Override
public CharSequence convertResultToString(Object resultValue) {
return ((CountryItem) resultValue).getCountryName();
}
};
}
如您所见，我的可观察字段是String类型。这个工作...有点。每当我从AutoCompleteTextView的下拉列表中选择一个国家时，它都会填充AutoCompleteTextView android:text字段；但是，我需要Country对象中的数据库ID才能在我们的另一个模型中使用它作为外键。
所以，我以为我会将可观察对象转换为Country类型，但这根本不起作用。一位同事说，我需要@BindingAdapter和@InverseBindingAdapter来完成这项工作，因此我创建了它们。
@BindingAdapter(value = {"android:text", "android:onItemSelected"}, requireAll = false)
public static void setText(AutoCompleteTextView autoCompleteTextView, Country newSelectedValue, final InverseBindingListener newTextAttrChanged)
{
autoCompleteTextView.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener()
{
@Override
public void onItemSelected(AdapterView<?> adapterView, View subView, int position, long id)
{
newTextAttrChanged.onChange();
}
@Override
public void onNothingSelected(AdapterView<?> adapterView)
{
}
});
if (newSelectedValue != null)
{
int pos = autoCompleteTextView.getListSelection();
autoCompleteTextView.setText(autoCompleteTextView.getAdapter().getItemViewType(pos));
}
}
@InverseBindingAdapter(attribute = "android:text", event = "android:onItemSelected")
public static Country getText(AutoCompleteTextView textView)
{
int pos = textView.getListSelection();
Country country = (Country) textView.getAdapter().getItem(pos);
return countryISO;
}
我的问题是，我的@BindingAdapter会在活动加载后立即被调用，但是再也不会...尤其是当我更改值时，这是我需要做的。
所以，我在做什么错，我该怎么做才能解决此问题？
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle? ): View? {
val application = requireNotNull(this.activity).application
val viewModelFactory = HomePageViewModelFactory(application)
val homePageViewModel = activity?.run {
ViewModelProviders.of(
this, viewModelFactory
).get(HomePageViewModel::class.java)
}
val binding: FragmentReviewPageBinding = DataBindingUtil.inflate(
inflater,
R.layout.fragment_review_page,
container,
false
)
binding.homePageViewModel = homePageViewModel
这是通过绑定链接xml变量的方式
binding.homePageViewModel = homePageViewModel
工厂类
class HomePageViewModelFactory(
private val application: Application) : ViewModelProvider.Factory {
@Suppress("unchecked_cast")
override fun <T : ViewModel?> create(modelClass: Class<T>): T {
if (modelClass.isAssignableFrom(HomePageViewModel::class.java)) {
return HomePageViewModel(application) as T
}
throw IllegalArgumentException("Unknown ViewModel class")
}
}
像这样，您可以在多个片段之间共享相同的viewmodel实例。