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我有一个ViewModel，旨在控制Activity或Fragment的状态。该视图模型包含4个ObservableBoolean被我的布局里面用来告诉视图必须可见或不可见：Android ObservableBoolean每次都不触发View.setVisibility
public class ContentLoaderViewModel extends BaseObservable {
public static final int LOADING_LAYOUT = 0;
public static final int CONTENT_LAYOUT = 1;
public static final int NO_DATA_LAYOUT = 2;
public static final int ERROR_LAYOUT = 3;
public final ObservableBoolean loading = new ObservableBoolean();
public final ObservableBoolean loaded = new ObservableBoolean();
public final ObservableBoolean noDataFound = new ObservableBoolean();
public final ObservableBoolean hasErrors = new ObservableBoolean();
@Bindable
public int displayedLayout;
public ContentLoaderViewModel() {
setDisplayedLayout(LOADING_LAYOUT);
}
public ContentLoaderViewModel(int displayedLayout) {
setDisplayedLayout(displayedLayout);
}
public int getDisplayedLayout() {
return displayedLayout;
}
public void setDisplayedLayout(int displayedLayout) {
this.displayedLayout = displayedLayout;
notifyPropertyChanged(BR.displayedLayout);
loading.set(displayedLayout == LOADING_LAYOUT);
loaded.set(displayedLayout == CONTENT_LAYOUT);
noDataFound.set(displayedLayout == NO_DATA_LAYOUT);
hasErrors.set(displayedLayout == ERROR_LAYOUT);
}
}
我用它在我的片段之一。这个片段旨在给出一个简单的界面来显示一个列表。一旦创建了适配器，它就会显示一个RecyclerView。适配器是异步创建的，然后RecyclerView被初始化。所以起初Fragment处于“加载”状态，当它接收到它的适配器时，它变成“内容”状态。下面是它的样子：
XML
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
xmlns:android="http://schemas.android.com/apk/res/android">
<data>
<import type="android.view.View" />
<variable
name="viewModel"
type="app.viewmodels.ContentLoaderViewModel" />
<variable
name="noDataText"
type="String" />
<variable
name="bottomButtonText"
type="String" />
<variable
name="showBottomButton"
type="boolean" />
</data>
<android.support.constraint.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<Button
android:text="@{bottomButtonText}"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:id="@+id/bottomButton"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
android:visibility="@{showBottomButton ? View.VISIBLE : View.GONE}"/>
<ProgressBar
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:visibility="@{viewModel.loading ? View.VISIBLE : View.GONE}"
tools:layout_constraintTop_creator="1"
tools:layout_constraintRight_creator="1"
tools:layout_constraintBottom_creator="1"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintRight_toRightOf="@+id/textView"
tools:layout_constraintLeft_creator="1"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintLeft_toRightOf="@+id/textView"
android:id="@+id/progressBar2" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@{noDataText}"
android:visibility="@{viewModel.noDataFound ? View.VISIBLE : View.GONE}"
android:id="@+id/textView"
tools:layout_constraintTop_creator="1"
tools:layout_constraintRight_creator="1"
app:layout_constraintRight_toRightOf="parent"
android:layout_marginTop="16dp"
tools:layout_constraintLeft_creator="1"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintTop_toTopOf="@+id/progressBar2" />
<android.support.v7.widget.RecyclerView
android:id="@+id/list"
android:layout_width="0dp"
android:layout_height="0dp"
android:layout_marginBottom="8dp"
android:visibility="@{viewModel.loaded ? View.VISIBLE : View.GONE}"
app:layout_constraintBottom_toTopOf="@+id/bottomButton"
app:layout_constraintHorizontal_bias="1.0"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.0" />
<include
layout="@layout/error_layout"
android:layout_width="0dp"
android:layout_height="0dp"
android:layout_marginRight="8dp"
app:layout_constraintRight_toRightOf="parent"
android:layout_marginLeft="8dp"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintBottom_toBottomOf="parent"
android:layout_marginBottom="8dp"
app:layout_constraintTop_toTopOf="parent"
android:layout_marginTop="8dp"
app:isVisible="@{viewModel.hasErrors}"/>
</android.support.constraint.ConstraintLayout>
</layout>
JAVA
@FragmentWithArgs
public class BaseListFragment extends BaseFragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
inflateBinding(inflater, container);
init(binding);
return binding.getRoot();
}
protected int getLayoutId() {
return R.layout.fragment_base_list;
}
protected void inflateBinding(LayoutInflater inflater, ViewGroup container) {
binding = DataBindingUtil.inflate(inflater, getLayoutId(), container, false);
onAttachToBinding(binding);
}
@Override
protected void init(final FragmentBaseListBinding binding) {
selectedItemPosition = -1;
restoreState();
initBinding(binding);
refresh();
}
private void initBinding(FragmentBaseListBinding binding) {
binding.setViewModel(new ContentLoaderViewModel());
binding.setNoDataText(noDataText);
binding.setBottomButtonText(bottomButtonText);
binding.setShowBottomButton(showBottomButton);
}
public void refresh() {
binding.getViewModel().setDisplayedLayout(ContentLoaderViewModel.LOADING_LAYOUT);
Observable<RecyclerView.Adapter> observableAdapter = Observable.fromCallable(new Callable<RecyclerView.Adapter>() {
@Override
public RecyclerView.Adapter call() throws Exception {
return hostAction.getAdapterAsync();
}
});
Observer<RecyclerView.Adapter> observerAdapter = new Observer<RecyclerView.Adapter>() {
@Override
public void onCompleted() {
}
@Override
public void onError(Throwable e) {
e.printStackTrace();
binding.getViewModel().setDisplayedLayout(ContentLoaderViewModel.ERROR_LAYOUT);
}
@Override
public void onNext(RecyclerView.Adapter adapter) {
initializeList(adapter);
}
};
adapterSubscription = observableAdapter
.subscribeOn((Schedulers.newThread()))
.observeOn(AndroidSchedulers.mainThread())
.subscribe(observerAdapter);
}
protected void initializeList(RecyclerView.Adapter adapter) {
this.adapter = adapter;
binding.list.setLayoutManager(hostAction.getLayoutManager());
binding.list.setAdapter(getFinalAdapter());
//Select first item by default
if(selectedItemPosition >= 0 && selectedItemPosition < adapter.getItemCount())
onItemClick(binding.list, null, selectedItemPosition, 0, null);
//Set item decoration (simple line under each items)
if(!hideDecorationItem)
binding.list.addItemDecoration(new SimpleItemDecoration(getContext(), 0));
binding.getViewModel().setDisplayedLayout(adapter.getItemCount() > 0
? ContentLoaderViewModel.CONTENT_LAYOUT
: ContentLoaderViewModel.NO_DATA_LAYOUT
);
Log.d(TAG, "initializeList: " + "viewModel.displayLayout[" + binding.getViewModel().getDisplayedLayout() + "]," +
" recyclerView.visibility[" + binding.list.getVisibility() + "], adapter.count[" + adapter.getItemCount() + "]");
binding.executePendingBindings();
binding.invalidateAll();
Log.d(TAG, "initializeList: (after pendingBinding)" + "viewModel.displayLayout[" + binding.getViewModel().getDisplayedLayout() + "]," +
" recyclerView.visibility[" + binding.list.getVisibility() + "], adapter.count[" + adapter.getItemCount() + "]");
}
protected RecyclerView.Adapter getFinalAdapter() {
return getWrapAdapter(adapter);
}
@NonNull
private WrapAdapter getWrapAdapter(RecyclerView.Adapter adapter) {
WrapAdapter wrapAdapter = new WrapAdapter(adapter);
wrapAdapter.setOnItemClickListener(binding.list, BaseListFragment.this);
return wrapAdapter;
}
}
而且我敢肯定，这是以数据绑定的，因为
- 的2日志
initializeList()显示t帽适配器具有项目：
d/BaseListFragment：initializeList：viewModel.displayLayout [1]，recyclerView.visibility [8]，adapter.count [27]
d/BaseListFragment：initializeList： （后pendingBinding）viewModel.displayLayout [1]，recyclerView.visibility [0]，adapter.count [27]
（令人奇怪的是这里具有执行未决的结合和所有无效后，可见性设置为0 - >View.VISIBLE但RecyclerView仍然不适用翼起来）
RecyclerView删除行android:visibility="@{viewModel.loaded ? View.VISIBLE : View.GONE}"它们是没有问题和RecyclerView始终可见。想知道这里发生了什么吗？
UPDATE
WrapAdapter是来自外部库的类：从GONE到INVISIBLE帮我https://github.com/eyeem/RecyclerViewTools/blob/master/library/src/main/java/com/eyeem/recyclerviewtools/adapter/WrapAdapter.java
我试图保持参照视图模型，而不是结合，但它似乎并没有改变任何东西。我把'initBinding'的第一行改成了'binding.setViewModel（viewModel = new ContentLoaderViewModel（））;'然后通过'viewModel'改变了'bindingView.getViewModel（）'的位置，而'viewModel'现在是我'fragment'的一个私有变量。这是你建议的吗？ 另外，你可以在我的更新中看到WrapAdapter来自哪里。你能告诉我为什么最好保持引用“ViewModel”而不是DataBinding对象（好奇心）的原因是什么？ – MHogge