我有一个活动，该活动具有一个SearchView，可用于输入查询，然后我的应用程序用于查询以访问API。我的活动还包含一个片段，在这个片段中，我有我的观察者。
此外，我还有ViewModel，它可以在查询时调用API。但是，我的观察者永远不会收到有关更新的通知，因此我的视图永远不会更新。除非我在启动时直接从ViewModel调用它。我将在这里专门显示：
ViewModel
class SearchViewModel : ViewModel() {
val booksResponse = MutableLiveData<MutableList<BookResponse>>()
val loading = MutableLiveData<Boolean>()
val error = MutableLiveData<String>()
init {
getBooks("How to talk to a widower")
}
fun getBooks(bookTitle: String) {
GoogleBooksService.api.getBooks(bookTitle).enqueue(object: Callback<ResponseWrapper<BookResponse>> {
override fun onFailure(call: Call<ResponseWrapper<BookResponse>>, t: Throwable) {
onError(t.localizedMessage)
}
override fun onResponse(
call: Call<ResponseWrapper<BookResponse>>,
response: Response<ResponseWrapper<BookResponse>>
) {
if (response.isSuccessful){
val books = response.body()
Log.w("2.0 getFeed > ", Gson().toJson(response.body()));
books?.let {
// booksList.add(books.items)
booksResponse.value = books.items
loading.value = false
error.value = null
Log.i("Content of livedata", booksResponse.getValue().toString())
}
}
}
})
}
private fun onError(message: String) {
error.value = message
loading.value = false
}
}
查询提交/活动
class NavigationActivity : AppCompatActivity(), SearchView.OnQueryTextListener, BooksListFragment.TouchActionDelegate {
lateinit var searchView: SearchView
lateinit var viewModel: SearchViewModel
private val mOnNavigationItemSelectedListener =
BottomNavigationView.OnNavigationItemSelectedListener { menuItem ->
when (menuItem.itemId) {R.id.navigation_search -> {
navigationView.getMenu().setGroupCheckable(0, true, true);
replaceFragment(SearchListFragment.newInstance())
return@OnNavigationItemSelectedListener true
}
R.id.navigation_books -> {
navigationView.getMenu().setGroupCheckable(0, true, true);
replaceFragment(BooksListFragment.newInstance())
return@OnNavigationItemSelectedListener true
}
}
false
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.main_activity)
replaceFragment(SearchListFragment.newInstance())
navigationView.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener)
//Set action bar color
val actionBar: ActionBar?
actionBar = supportActionBar
val colorDrawable = ColorDrawable(Color.parseColor("#FFDAEBE9"))
// actionBar!!.setBackgroundDrawable(colorDrawable)
// actionBar.setTitle(("Bobs Books"))
setSupportActionBar(findViewById(R.id.my_toolbar))
viewModel = ViewModelProvider(this).get(SearchViewModel::class.java)
}
override fun onBackPressed() {
super.onBackPressed()
navigationView.getMenu().setGroupCheckable(0, true, true);
}
private fun replaceFragment(fragment: Fragment){
supportFragmentManager
.beginTransaction()
.replace(R.id.fragmentHolder, fragment)
.commit()
}
override fun onCreateOptionsMenu(menu: Menu): Boolean {
menuInflater.inflate(R.menu.book_search_menu, menu)
val searchItem = menu.findItem(R.id.action_search)
searchView = searchItem.actionView as SearchView
searchView.setOnQueryTextListener(this)
searchView.queryHint = "Search for book"
/*searchView.onActionViewExpanded()
searchView.clearFocus()*/
// searchView.setIconifiedByDefault(false)
return true
}
override fun onQueryTextSubmit(query: String): Boolean {
//replaces fragment if in BooksListFragment when searching
replaceFragment(SearchListFragment.newInstance())
val toast = Toast.makeText(
applicationContext,
query,
Toast.LENGTH_SHORT
)
toast.show()
searchView.setQuery("",false)
searchView.queryHint = "Search for book"
// viewModel.onAddBook(Book(title = query!!, rating = 5, pages = 329))
Log.i("Query fra text field", query)
// viewModel.getBooks(query)
return false
}
override fun onQueryTextChange(newText: String?): Boolean {
return false
}
override fun launchBookFragment(bookId: Book) {
supportFragmentManager
.beginTransaction()
.replace(R.id.fragmentHolder, com.example.bobsbooks.create.BookFragment.newInstance(bookId.uid))
.addToBackStack(null)
.commit()
navigationView.getMenu().setGroupCheckable(0, false, true);
}
}
片段
class SearchListFragment : Fragment() {
lateinit var viewModel: SearchViewModel
lateinit var contentListView: SearchListView
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_search_list, container, false).apply {
contentListView = this as SearchListView
}
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
bindViewModel()
setContentView()
}
private fun setContentView(){
contentListView.initView()
}
private fun bindViewModel(){
Log.i("ViewmodelCalled", "BindViewModel has been called")
viewModel = ViewModelProvider(this).get(SearchViewModel::class.java)
viewModel.booksResponse.observe(viewLifecycleOwner, Observer {list ->
list?.let {
Log.i("Observer gets called", "Updatelistgetscalled")
contentListView.updateList(list)
}
} )
viewModel.error.observe(viewLifecycleOwner, Observer { errorMsg ->
})
viewModel.loading.observe(viewLifecycleOwner, Observer { isLoading ->
})
}
companion object {
fun newInstance(): SearchListFragment {
return SearchListFragment()
}
}
当我将getBooks调用放入Viewmodel Init时，它将正确执行所有操作。它通过API获取书本响应，将其添加到我的LiveData中并通知我的适配器。
但是，如果我改为删除它并通过我的Activity中的Querysubmit调用它，它将根据我的日志获取数据并将其放入我的bookReponse：LiveData中，但这仅是它的全部。从未通知观察者此更改，因此适配器从不知道它有新数据来填充其视图。
我觉得我已经尝试了所有方法，甚至在另一个应用程序中也使用了相同的代码，该代码完全在活动中运行，而不是在活动中进行查询，其余部分在我的片段中调用。我最好的猜测是这会产生影响，但是我不知道如何。
答案 0 :(得分：0)
根据您的解释
但是，如果我改为删除它并通过我的Activity中的Querysubmit调用它，它将根据我的日志获取数据并将其放入我的bookReponse：LiveData中，但这仅是它的全部。从未通知观察者此更改，因此适配器从不知道它有新数据来填充其视图。
问题是您要在活动和片段中都初始化SearchViewModel，所以片段没有SearchViewModel的相同实例，而是应该在片段中使用共享viewmodel，如：
viewModel = ViewModelProvider(activity).get(SearchViewModel::class.java)