ListView可以出现在Activity中但不能出现在Fragment中

Question

ListView 可以出现在 Activity 但不能出现在 Fragment 但是我在 Kotlin 中使用与 Android Studio 3.0 相同的代码？

这是我的片段代码：

class testFrag : Fragment() {
var adapter : mo3dAdapter?=null
var listOfMkabala = ArrayList<MeetingDetails>()


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


    listOfMkabala .add ( MeetingDetails(" nour1", "ahmed1" , "aya1"))
    listOfMkabala .add ( MeetingDetails(" nour2", "ahmed2" , "aya2"))
    listOfMkabala .add ( MeetingDetails(" nour3", "ahmed3" , "aya3"))
    listOfMkabala .add ( MeetingDetails(" nour4", "ahmed4" , "aya4"))
    listOfMkabala .add ( MeetingDetails(" nour5", "ahmed5" , "aya5"))
    listOfMkabala .add ( MeetingDetails(" nour6", "ahmed6" , "aya6"))


    adapter = mo3dAdapter (context  ,listOfMkabala)
    tv1.adapter = adapter

}


fun test ( view: View){

}

这是我的适配器：

inner class mo3dAdapter: BaseAdapter {
    var  listOfMkabaln= ArrayList<MeetingDetails>()
    var context:Context?=null
    constructor(context:Context, listOfMkabaln: ArrayList<MeetingDetails>):super(){
        this.listOfMkabaln=listOfMkabaln
        this.context=context
    }

    override fun getView(p0: Int, p1: View?, p2: ViewGroup?): View {
        val mo3d =  listOfMkabaln[p0]

        var inflator = context!!.getSystemService(Context.LAYOUT_INFLATER_SERVICE) as LayoutInflater
        var myView = inflator.inflate(R.layout.fragment_test, null)
        myView.text1.text = mo3d.name1!!
        myView.text2.text = mo3d.name2!!
        myView.text3.text = mo3d.name3!!

        return myView

    }

    override fun getItem(p0: Int): Any {
        return listOfMkabaln[p0]
    }

    override fun getItemId(p0: Int): Long {
        return p0.toLong()
    }

    override fun getCount(): Int {

        return  listOfMkabaln.size
    }

}

Answer 1

你应该在你的初始化之后做一个return语句 onCreateView().

您正在使用kotlin-android-extensions 直接获取您的视图。如果您使用这种方式，则只有在视图创建后才能获得LisView。

你的代码应该是这样的。

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

override fun onViewCreated(view: View?, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
    listOfMkabala .add ( MeetingDetails(" nour1", "ahmed1" , "aya1"))
    listOfMkabala .add ( MeetingDetails(" nour2", "ahmed2" , "aya2"))
    listOfMkabala .add ( MeetingDetails(" nour3", "ahmed3" , "aya3"))
    listOfMkabala .add ( MeetingDetails(" nour4", "ahmed4" , "aya4"))
    listOfMkabala .add ( MeetingDetails(" nour5", "ahmed5" , "aya5"))
    listOfMkabala .add ( MeetingDetails(" nour6", "ahmed6" , "aya6"))
    adapter = mo3dAdapter (context  ,listOfMkabala)
    tv1.adapter = adapter
}

onViewCreated() 在视图创建后运行。因此它确保您的视图已经创建。

您也为适配器传递了相同的布局。

在您的适配器代码中，将 R.layout.fragment_test 更改为您的模型布局。

var myView = inflator.inflate(R.layout.fragment_test, null)

希望对你有帮助:)

Answer 2

您在return 语句之后在onCreateView 中编写了代码，我们称之为死代码（无法访问的代码）。以这种方式，您永远不会在ListView 中设置您的适配器。

遵循 3 个步骤作为一般方法 -

1. 在onCreate 方法中初始化所有数据。在您的情况下，ArrayList 中的数据将添加到那里。

所以看起来像 -

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    listOfMkabala .add ( MeetingDetails(" nour1", "ahmed1" , "aya1"))
    listOfMkabala .add ( MeetingDetails(" nour2", "ahmed2" , "aya2"))
    listOfMkabala .add ( MeetingDetails(" nour3", "ahmed3" , "aya3"))
    listOfMkabala .add ( MeetingDetails(" nour4", "ahmed4" , "aya4"))
    listOfMkabala .add ( MeetingDetails(" nour5", "ahmed5" , "aya5"))
    listOfMkabala .add ( MeetingDetails(" nour6", "ahmed6" , "aya6"))
}

1. 仅在onCreateView 中初始化您的布局资源。像这样——

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

2. 这与在 UI 上呈现数据有关，应该在 onViewCreated 方法中完成。在你的情况下，它应该像 -

   override fun onViewCreated(view: View?, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        adapter = mo3dAdapter (context  ,listOfMkabala)
        // Init your listview
        tv1 = view?.findViewById(R.id.your_listview_id);
        tv1.adapter = adapter
   }
   

确保您初始化tv1，它应该是ListView 引用。