我正在为Android应用程序使用Toothpick依赖项注入框架,当在Backstack上存在相同片段的多个实例时,我无法将Android ViewModels注入片段。我希望每个片段实例都拥有自己的viewmodel实例,但是问题是只有一个viewmodel被创建并在所有片段实例之间共享。
我创建了一个示例项目来演示该问题。单个活动包含带有Android视图模型的单个片段。创建了该活动的多个实例,并将其放置在活动的堆栈中。
这是我的活动:
class MainActivity : FragmentActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.my_layout)
}
}
它包含此布局:
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
<fragment
android:id="@+id/main_fragment"
android:name="no.knowit.android.tptest.MainFragment"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</FrameLayout>
MainFragment:
class MainFragment : Fragment() {
companion object {
const val TAG = "MainFragment"
}
@Inject
lateinit var viewModel: MainViewModel
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
openScope()
}
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
val v = inflater.inflate(R.layout.main_fragment_layout, container, false)
v.findViewById<Button>(R.id.spawn_button).setOnClickListener {
Log.i(TAG, "spawn")
val i = Intent(context, MainActivity::class.java)
startActivity(i)
}
return v
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
Log.i(TAG, "fragment " + System.identityHashCode(this))
Log.i(TAG, "viewModel " + System.identityHashCode(viewModel))
Log.i(TAG, "liveData " + System.identityHashCode(viewModel.myLiveData))
}
protected fun openScope() {
val scope = KTP.openScopes(ApplicationScope::class.java)
.openSubScope(ViewModelScope::class.java)
installViewModelBindings(scope)
scope.closeOnViewModelCleared(this)
.openSubScope(activity!!)
.closeOnDestroy(activity!!)
.openSubScope(this)
.closeOnDestroy(this)
scope.inject(this)
}
private fun installViewModelBindings(scope: Scope) {
scope.installViewModelBinding<MainViewModel>(this)
}
}
MainViewModel:
class MainViewModel : ViewModel() {
@Inject
lateinit var myLiveData: MyLiveData
}
MyLiveData:
class MyLiveData @Inject constructor(): LiveData<Int>() {
}
输出:
2020-02-18 09:12:56.325 23253-23253/no.knowit.android.tptest I/MainFragment: fragment 45659892
2020-02-18 09:12:56.326 23253-23253/no.knowit.android.tptest I/MainFragment: viewModel 236316818
2020-02-18 09:12:56.326 23253-23253/no.knowit.android.tptest I/MainFragment: liveData 241221950
2020-02-18 09:13:03.472 23253-23253/no.knowit.android.tptest I/MainFragment: spawn
2020-02-18 09:13:03.632 23253-23253/no.knowit.android.tptest I/MainFragment: fragment 8599012
2020-02-18 09:13:03.632 23253-23253/no.knowit.android.tptest I/MainFragment: viewModel 236316818
2020-02-18 09:13:03.632 23253-23253/no.knowit.android.tptest I/MainFragment: liveData 241221950
2020-02-18 09:13:05.194 23253-23253/no.knowit.android.tptest I/MainFragment: spawn
2020-02-18 09:13:05.289 23253-23253/no.knowit.android.tptest I/MainFragment: fragment 130024810
2020-02-18 09:13:05.289 23253-23253/no.knowit.android.tptest I/MainFragment: viewModel 236316818
2020-02-18 09:13:05.289 23253-23253/no.knowit.android.tptest I/MainFragment: liveData 241221950
2020-02-18 09:13:06.436 23253-23253/no.knowit.android.tptest I/MainFragment: spawn
如您所见,将创建新的片段,但是它们共享相同的视图模型和实时数据。我想为每个片段创建一个新的viewmodel / livedata,并且这些viewmodel应该存在于viewmodel范围内。我该怎么做?
您可以使用自定义ViewModelFactory