微调监听器LiveData问题 [英] Spinner Listener LiveData Issue
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问题描述
在我的片段中，我有两个微调工具。
两者都由在ViewModel中观察到的LiveData填充，如下所示：
数据-lang="js"数据-隐藏="假"数据-控制台="真"数据-巴贝尔="假"> // Observe Filtered ProductGroups and populate Spinner
businessViewModel.filteredAppDataProductGroups.observe(viewLifecycleOwner, { productGroupArrayList ->
if (!productGroupArrayList.isNullOrEmpty()){
val adapter = ArrayAdapter(requireContext(), android.R.layout.simple_spinner_dropdown_item, productGroupArrayList)
binding.inventoryAddEditProductGroupSpinner.adapter = adapter
}
})
// Observe Filtered ProductTypes and populate Spinner
businessViewModel.filteredAppDataProductTypes.observe(viewLifecycleOwner, { productTypeArrayList ->
if (productTypeArrayList != null){
val adapter = ArrayAdapter(requireContext(), android.R.layout.simple_spinner_dropdown_item, productTypeArrayList)
binding.inventoryAddEditProductTypeSpinner.adapter = adapter
}
})这很好用，但我正在尝试根据当前选择的第一个微调控件来过滤第二个微调控件中的数据，方法是设置一个侦听器并更新视图模型数据，如下所示：
数据-lang="js"数据-隐藏="假"数据-控制台="真"数据-巴贝尔="假"> binding.inventoryAddEditProductGroupSpinner.onItemSelectedListener = object: AdapterView.OnItemSelectedListener{
override fun onItemSelected(parent:AdapterView<*>, view: View, position: Int, id: Long){
val productGroupObject = parent.selectedItem as ProductGroupObject
if (productGroupObject.productGroupID.isNotEmpty()){
businessViewModel.updateCurrentProductGroupVMLiveData(productGroupObject.productGroupID)
}
}
override fun onNothingSelected(parent: AdapterView<*>){
}
}更新ViewModel中的筛选列表，如下所示：
数据-lang="js"数据-隐藏="假"数据-控制台="真"数据-巴贝尔="假"> fun updateCurrentProductGroupVMLiveData (currentProductGroupId: String) {
val newProductGroup = allAppDataProductGroups.value?.find { productGroup -> productGroup.productGroupID == currentProductGroupId }
_currentProductGroup.value = newProductGroup
if(newProductGroup?.productGroup != null) {
val filteredProductsList = allAppDataProductTypes.value?.filter { productTypeObject -> productTypeObject.productGroup == newProductGroup.productGroup} as ArrayList<ProductTypeObject>
_filteredAppDataProductTypes.value = filteredProductsList
}
Log.d(TAG, "updateCurrentProductGroupVMLiveData(): '_currentProductGroupId.value' updated ($currentProductGroupId)")
}但是，如果我将显示的代码添加到onItemSelected中，应用程序会崩溃，并看到以下错误：
数据-lang="js"数据-隐藏="假"数据-控制台="真"数据-巴贝尔="假"> --------- beginning of crash
2021-10-06 23:06:34.740 17510-17510/com.xxxxx.acorn E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.locators.acorn, PID: 17510
java.lang.NullPointerException: Parameter specified as non-null is null: method kotlin.jvm.internal.Intrinsics.checkNotNullParameter, parameter view
at com.xxxxx.acorn.business.inventory.InventoryAddEditFragment$setSpinnerListeners$2.onItemSelected(InventoryAddEditFragment.kt)
at android.widget.AdapterView.fireOnSelected(AdapterView.java:931)
at android.widget.AdapterView.dispatchOnItemSelected(AdapterView.java:920)
at android.widget.AdapterView.-wrap1(AdapterView.java)
at android.widget.AdapterView$SelectionNotifier.run(AdapterView.java:890)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6077)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:756)