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Navigation Component: How to set drawer with toolbar in each fragment(2个答案)
5天前关闭。
我尝试了一些东西,但无法修复此错误,这是我的主活动代码
class MainActivity : AppCompatActivity() {
private lateinit var binding : ActivityMainBinding
private lateinit var navController: NavController
lateinit var viewModel : NewsViewModel
val db : ArticleDatabase? = null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = ActivityMainBinding.inflate(layoutInflater)
setContentView(binding.root)
val newsRepository = NewsRepository(ArticleDatabase(this))
val viewModelProviderFactory = NewsViewModelProviderFactory(newsRepository)
viewModel = ViewModelProvider(this,viewModelProviderFactory)[NewsViewModel::class.java]
navController = Navigation.findNavController(this, R.id.newsNavHostFragment)
setupWithNavController(binding.bottomNavigationView,navController)
}
}
这是片段代码
class BrakingNewsFragment : Fragment() {
lateinit var viewModel : NewsViewModel
lateinit var newsAdapter : NewsAdapter
private lateinit var binding : FragmentBrakingNewsBinding
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
}
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
// Inflate the layout for this fragment
binding = FragmentBrakingNewsBinding.inflate(inflater,container,false)
return binding.root
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
viewModel = (activity as MainActivity).viewModel
setUpRecyclerView()
viewModel.breakingNews.observe(viewLifecycleOwner, Observer { response ->
when(response){
is Resource.Succes -> {
response.data?.let {
newsAdapter.differ.submitList(it.articles)
}
}
is Resource.Loading -> {
println("abcabc")
}
}
})
}
private fun setUpRecyclerView(){
newsAdapter = NewsAdapter()
binding.breakingNewsRecyclerView.apply {
adapter = newsAdapter
layoutManager = LinearLayoutManager(activity)
}
}
}
这是一个很好的例子。
class NewsViewModelProviderFactory(private val newsRepository: NewsRepository) : ViewModelProvider.Factory {
override fun <T : ViewModel> create(modelClass: Class<T>): T {
return NewsViewModel(newsRepository) as T
}
}
logcat错误在这里
原因:android.view.InflateException:二进制XML文件行#19在com.example. newsletter kotlin:layout/activity_main中:二进制XML文件行#19在com.example. newsletter kotlin:layout/activity_main中:膨胀类片段时出错,原因:android.view.InflateException:二进制XML文件行#19在com.example. newsletter kotlin:layout/activity_main中:膨胀类片段时出错,原因:Kotlin. UninitializedPropertyException:lateinit属性viewModel尚未初始化
如何才能修复
1条答案
按热度按时间hk8txs481#
你不能这样示例化视图模型:
为什么不使用
或者因为这可能是一个带有Activity的sharedViewModel:
在执行此操作之前,您需要viewModels的Kotlin扩展依赖项。