Android 如何使用Kotlin修复此错误，找不到片段构造函数？
我正在使用Kotlin开发Android 如何使用Kotlin修复此错误，找不到片段构造函数？,android,android-fragments,kotlin,Android,Android Fragments,Kotlin,我正在使用Kotlin开发Android应用程序。在我的应用程序中，包含Tab和ViewPager，因此我实现了这两个选项卡。当我移动到另一个活动并compack to Tab view activity时，应用程序将停止运行，并且logcat在错误下方显示 java.lang.RuntimeException:无法启动活动组件信息{com.crypto.wallet/com.crypto.wallet.activities.MainActivity}:android.support.v4.ap
AndroidTabViewPagerlogcat@SuppressLint("ValidFragment")
class ReceiveFragment(private val transactionList: List<TransactionEntity>, val appDatabase: AppDatabase, private val direction: TransactionAdapterDirection,
val networkDefinitionProvider: NetworkDefinitionProvider) : Fragment(){
private var linearLayoutManager: LinearLayoutManager? = null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
}
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
val rootView = inflater.inflate(R.layout.receive_fragment, container, false)
val recyclerView = rootView.findViewById<RecyclerView>(R.id.transaction_recycler_in) as RecyclerView
linearLayoutManager = LinearLayoutManager(getActivity(), LinearLayout.VERTICAL, false)
recyclerView.layoutManager = linearLayoutManager
recyclerView.adapter = TransactionRecyclerAdapter(transactionList,appDatabase,direction,networkDefinitionProvider)
recyclerView.setHasFixedSize(true);
return rootView
}
}
override fun getItem(position: Int): Fragment? {
var fragment: Fragment? = null
when (position) {
//0 -> fragment = ReceiveFragment(MytransactionList,MyappDatabase,Myincoming,MynetworkDefinitionProvider)
0 -> fragment = ReceiveFragment(MyIT,MyAppDatabase,MyIncoming,MyNetwork)
1 -> fragment = SendFragment()
}
return fragment
}
当您获得有关错误的简短描述时，您将看到： 避免在片段中使用非默认构造函数：使用默认构造函数加上
片段setArguments（Bundle）setArguments（Bundle）getArguments（） fun newInstance(bundle : Bundle) : ReceiveFragment{
val fragment = ReceiveFragment()
fragment.arguments=bundle
return fragment
}
0 -> fragment = ReceiveFragment.newInstance(new Bundle)
更多信息：您可以做的是创建一个具有零参数的默认构造函数
companion object {
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* @param param1 Parameter 1.
* @param param2 Parameter 2.
* @return A new instance of fragment LoginFragment.
*/
// TODO: Rename and change types and number of parameters
@JvmStatic
fun newInstance(param1: String, param2: String) =
ReceiveFragment().apply {
arguments = Bundle().apply {
putString(ARG_PARAM1, param1)
putString(ARG_PARAM2, param2)
}
// Or from your code, you can use Gson
val prefs = applicationContext.getSharedPreferences("MyPref", 0)
val gson = Gson()
val json = prefs.getString("MyObject", "")
val person1: List<TransactionEntity> = gson.fromJson(json,
ArrayList<TransactionEntity>()::class.java)
}
}
onCreate override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
arguments?.let {
email = it.getString(ARG_PARAM1)
password = it.getString(ARG_PARAM2)
}
// Or from your code, you can use Gson
val prefs = applicationContext.getSharedPreferences("MyPref", 0)
val gson = Gson()
val json = prefs.getString("MyObject", "")
val person1: List<TransactionEntity> = gson.fromJson(json,
ArrayList<TransactionEntity>()::class.java)
}
希望这有助于片段应该有一个带有0个参数的默认构造函数。在片段中使用非默认构造函数是一种不好的做法。请使用
singleton构造函数，我将尝试您的技巧@VladyslavMatviienko@VladyslavMatviienko，是的，当活动重新创建时，在某些情况下，它可以调用默认构造函数。我将检查并实现此构造函数。请检查以下答案：是。我对此表示怀疑，我的参数不是字符串类型，而是自定义类型。就像“列表”一样，我如何才能添加到putString（）。。。？？？？？？e、 g:fun newInstance（myIT:List，myAppDatabase:AppDatabase，myIncoming:TransactionaAdapterDirection，myNetwork:NetworkDefinitionProvider），因此只需替换为您的参数，例如：）好的，没有参数它就无法正常工作。我可以在这里使用GSON吗？是的，当然可以，在newInstance
方法中，让我为您编辑一点我需要在newInstance（）中获取此参数，而不是在oncreate（）中获取此“putString（ARG_PARAM1，PARAM1）putString（ARG_PARAM2，PARAM2）”我需要使用GSON
fun newInstance(bundle : Bundle) : ReceiveFragment{
val fragment = ReceiveFragment()
fragment.arguments=bundle
return fragment
}
0 -> fragment = ReceiveFragment.newInstance(new Bundle)
companion object {
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* @param param1 Parameter 1.
* @param param2 Parameter 2.
* @return A new instance of fragment LoginFragment.
*/
// TODO: Rename and change types and number of parameters
@JvmStatic
fun newInstance(param1: String, param2: String) =
ReceiveFragment().apply {
arguments = Bundle().apply {
putString(ARG_PARAM1, param1)
putString(ARG_PARAM2, param2)
}
// Or from your code, you can use Gson
val prefs = applicationContext.getSharedPreferences("MyPref", 0)
val gson = Gson()
val json = prefs.getString("MyObject", "")
val person1: List<TransactionEntity> = gson.fromJson(json,
ArrayList<TransactionEntity>()::class.java)
}
}
0 -> receiveFragment= ReceiveFragment.newInstance(firstParam, secondParam)
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
arguments?.let {
email = it.getString(ARG_PARAM1)
password = it.getString(ARG_PARAM2)
}
// Or from your code, you can use Gson
val prefs = applicationContext.getSharedPreferences("MyPref", 0)
val gson = Gson()
val json = prefs.getString("MyObject", "")
val person1: List<TransactionEntity> = gson.fromJson(json,
ArrayList<TransactionEntity>()::class.java)
}
class ReceiveFragment: Fragment()