kotlin：如何在两个片段之间传递数据

Question

我有一个简单的应用程序，它有一个 Activity 、 RecyclerView 适配器、 RecyclerView 片段和其他片段来显示我在 RecyclerView 中单击的那个项目的数据，但我的问题是我不知道如何传递数组行的数据新片段显示后的点击乐趣

MainActivity.kt

class MainActivity : AppCompatActivity(),ContentAdapter.ContentListener{
override fun onItemClicked(item: MainMarketTickClass) {
        var ft1 : FragmentTransaction = supportFragmentManager.beginTransaction()
        ft1.replace(R.id.MainFrame,AddCar.newInstanceaddcar())
        ft1.commit()}
override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)

    setContentView(R.layout.activity_main)
    var bnv = findViewById(R.id.navigation) as BottomNavigationView
    bnv.setOnNavigationItemSelectedListener (object : BottomNavigationView.OnNavigationItemSelectedListener{
        override fun onNavigationItemSelected(item: MenuItem): Boolean {
            var selectFragment : Fragment? = null
            when (item.itemId) {
                R.id.navigation_home -> {
                    selectFragment = MainMarket.newInstance()
                }
                R.id.navigation_dashboard -> {
                   selectFragment = AddCar.newInstanceaddcar()
                }
                R.id.navigation_notifications -> {

                }
            }
            var ft : FragmentTransaction = supportFragmentManager.beginTransaction()
            ft.replace(R.id.MainFrame,selectFragment)
            ft.commit()
            return true
        }
    })

    var ft : FragmentTransaction = supportFragmentManager.beginTransaction()
    ft.replace(R.id.MainFrame,MainMarket.newInstance())
    ft.commit()
}

}

ContentAdapter.kt

class ContentAdapter constructor(private val activity: MainActivity, private var listOfData: ArrayList<MainMarketTickClass>, val listener: ContentListener) : RecyclerView.Adapter<ContentAdapter.ViewHolder>() {

override fun getItemCount(): Int = listOfData.size
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
    var inf = ViewHolder(LayoutInflater.from(parent!!.context).inflate(R.layout.maintick, parent, false))
    return inf

}

override fun onBindViewHolder(holder: ViewHolder, position: Int) {
    holder.bind(listOfData, listener)
}

class ViewHolder(itemView: View?) : RecyclerView.ViewHolder(itemView) {

    fun bind(listOfData: ArrayList<MainMarketTickClass>, listener: ContentListener) {
        val dataListin2 = listOfData[adapterPosition]

        itemView.textView.text = dataListin2.title

       interface method implemented in the Activity
        itemView.setOnClickListener {
            listener.onItemClicked(listOfData.get(adapterPosition))
        }
    }
}

public interface ContentListener {
    fun onItemClicked(item: MainMarketTickClass)
}

MainMarket.kt

class MainMarket: Fragment(),ContentAdapter.ContentListener{

var ITEMSList = ArrayList<MainMarketTickClass>()
companion object {
   fun newInstance():Fragment{

       var fb : MainMarket = MainMarket()
       return fb
   }
}


override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
    var inf = inflater!!.inflate(R.layout.main_marker,container,false)
    return inf


}

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {

    ITEMSList .add ( MainMarketTickClass("123"))
    ITEMSList .add ( MainMarketTickClass(" 123"))
    ITEMSList .add ( MainMarketTickClass("123"))


    var adapter = ContentAdapter (MainActivity(),ITEMSList,this)
    list.adapter = adapter
    list.layoutManager = LinearLayoutManager(this.context,LinearLayoutManager.VERTICAL,false)

}

override fun onItemClicked(item: MainMarketTickClass) {
    if(activity is MainActivity){
        (activity as MainActivity).onItemClicked(item)

    }

}

addcar.kt

class AddCar: Fragment(), ContentAdapter.ContentListener{


companion object {
   fun newInstanceaddcar(): Fragment {

       var fb : AddCar = AddCar()
       val args = Bundle()

       fb.arguments = args

       return fb
   }
}





override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
    return inflater!!.inflate(R.layout.add_car,container,false)



}

 override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
     val TextView= view!!.findViewById(R.id.textView) as TextView
     var titlein = ""

}
override fun onItemClicked(item: MainMarketTickClass) {


}

Answer 1

您应该将特定位置的单个数据传递给您的ViewHolder，而不是将ContentAdapter 中的listOfData 传递给ViewHolder。这里我对你的ContentAdapter做一个修改：

override fun onBindViewHolder(holder: ViewHolder, position: Int) {
    holder.bind(listOfData[position], listener)
}

你的ViewHolder 应该是这样的：

class ViewHolder(itemView: View?) : RecyclerView.ViewHolder(itemView) {

    fun bind(data: MainMarketTickClass, listener: ContentListener) {
        itemView.setOnClickListener {
            listener.onItemClicked(data)
        }
    }
}

要在片段之间传输数据，您可能需要阅读 Communicating with Other Fragments。你的ContentListener 应该在MainMarket：

class MainMarket: Fragment() {
private lateinit var mCallback: ContentListener

// Container Activity must implement this interface
interface ContentListener {
    fun onItemClicked(item: String)
}

override fun onAttach(context: Context?) {
    super.onAttach(context)
    // This makes sure that the container activity has implemented
    // the callback interface. If not, it throws an exception
    try {
        mCallback = context as ContentListener
    } catch (e: ClassCastException) {
        throw ClassCastException(activity.toString()
                + " must implement OnHeadlineSelectedListener")
    }
}

并在您的Activity 中实现ContentListener

class MainActivity : AppCompatActivity(), MainMarket.ContentListener {

override fun onItemClicked(item: MainMarketTickClass) {
    val bundle = Bundle()
    bundle.putParcelable("data", item)

    val addCar = AddCar()
    addCar.arguments = bundle

    var ft : FragmentTransaction = supportFragmentManager.beginTransaction()
    ft.replace(R.id.frameLayout,addCar)
    ft.commit()
}

如果你想把你的对象带到另一个片段，你应该考虑用Parcelable来实现你的对象。这是Send object using parcelable 的一些示例。
希望对你有帮助。

Answer 2

这是一个对我有用的好教程。在本教程中，我们在第一个片段中创建一个包，然后我们将其放入该包中。最后，我们使用它的参数将数据发送到第二个包。

Kotlin Tutorial: Transfer data between Fragments -Android Studio Tutorials

Answer 3

片段之间传递数据的方式有：

• 捆绑（首选）
• 共享首选项
• 数据库

因此，在您的newInstanceaddcar(): Fragment 作为您需要的参数数据传递中，set 使用bundle.putType()（其中类型为 Int、Boolean、Serializable 等），并在您的片段代码中使用bundle.getType() 获取这些数据。 这样您就可以将任何可序列化类型传递给其他片段。