我想在一个fragment中创建一个recyclerView，但是出现了一个错误：“java.lang.IllegalStateException: recylerView_Main不能为空 at com.gph.bottomnavigation.FragmentMe.onCreateView(FragmentMe.kt:28)”
- 问题1）请帮忙解决这个问题。
- 问题2）我在一个没有任何fragment的空项目中创建了一个recyclerView，它可以正常工作。
但是同样的代码在Fragment中无法工作，显示错误，所以我将"recylerView_Main.layoutManager = LinearLayoutManager(this)"更改为"recylerView_Main.layoutManager = LinearLayoutManager(context)"。它没有显示错误，我可以在模拟器上运行，但是当我点击Fragment的导航按钮时，应用程序停止并显示此错误。请帮忙解决。
这里是FragmentMe.kt的代码：
class FragmentMe : Fragment() {
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?): View? {
recylerView_Main.layoutManager = LinearLayoutManager(context)
recylerView_Main.adapter = Mainadapter()
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_me, container, false)
}
}
这里是MainActivity.kt的代码：
class MainActivity : AppCompatActivity() {
val manager = supportFragmentManager
private val mOnNavigationItemSelectedListener = BottomNavigationView.OnNavigationItemSelectedListener { item ->
when (item.itemId) {
R.id.navigation_home -> {
//message.setText(R.string.title_home)
createFragmentQpon()
return@OnNavigationItemSelectedListener true
}
R.id.navigation_dashboard -> {
//message.setText(R.string.title_dashboard)
createFragmentMe()
return@OnNavigationItemSelectedListener true
}
R.id.navigation_notifications -> {
//message.setText(R.string.title_notifications)
createFragmentTools()
return@OnNavigationItemSelectedListener true
}
}
false
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
//Action Bar
val actionBar = supportActionBar
actionBar!!.setDisplayShowHomeEnabled(true)
actionBar.setBackgroundDrawable(ColorDrawable(Color.parseColor("#00FFFFFF")))
actionBar.setIcon(R.drawable.ic_home_black_24dp)
actionBar.setDisplayShowTitleEnabled(false)
createFragmentQpon()
navigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener)
}
fun createFragmentQpon() {
val transaction = manager.beginTransaction()
val fragment = FragmentQpon()
transaction.replace(R.id.fragmentholder,fragment)
transaction.addToBackStack(null)
transaction.commit()
}
fun createFragmentMe() {
val transaction = manager.beginTransaction()
val fragment = FragmentMe()
transaction.replace(R.id.fragmentholder,fragment)
transaction.addToBackStack(null)
transaction.commit()
}
fun createFragmentTools() {
val transaction = manager.beginTransaction()
val fragment = FragmentTools()
transaction.replace(R.id.fragmentholder,fragment)
transaction.addToBackStack(null)
transaction.commit()
}
}
这里是Mainadapter.kt的代码：
class Mainadapter: RecyclerView.Adapter<CustomViewHolder>() {
val videolist = listOf("aaa","bbbb","cccc")
override fun getItemCount(): Int {
return 3
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): CustomViewHolder {
val layoutInflater = LayoutInflater.from(parent?.context)
val cellForRow = layoutInflater.inflate(R.layout.tutorial_layout, parent, false)
return CustomViewHolder(cellForRow)
}
override fun onBindViewHolder(holder: CustomViewHolder, position: Int) {
var videoName = videolist.get(position)
holder.itemView.title.text = videoName
}
}
class CustomViewHolder(v: View): RecyclerView.ViewHolder(v) {
}