【发布时间】：2017-10-02 12:21:27
【问题描述】：
我正在尝试用 PickPowerFragment 片段替换 MainFragment 片段，但是当我按下 MainFragment 中的按钮以将 MainFragment 替换为 PickPowerFragment 时，应用程序崩溃了。 我能够按照教程中的说明在 java 中成功加载 PickPowerFragment，但是当我尝试在 Kotlin 中这样做时应用程序崩溃（仅供练习）。 那么如何使用 Kotlin 语法替换 Fragment
activity_hero_me.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.mandar.herome.Activities.HeroMe"
tools:layout_editor_absoluteX="0dp"
tools:layout_editor_absoluteY="25dp">
<FrameLayout
android:id="@+id/ReplaceFrame"
android:layout_width="0dp"
android:layout_height="0dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.0">
</FrameLayout>
</android.support.constraint.ConstraintLayout>
HeroMe.kt
package com.example.mandar.herome.Activities
import android.app.Activity
import android.app.Fragment
import android.app.FragmentManager
import android.net.Uri
import android.os.Bundle
import com.example.mandar.herome.Fragments.MainFragment
import com.example.mandar.herome.Fragments.PickPowerFragment
import com.example.mandar.herome.R
class HeroMe : Activity() , MainFragment.OnMainFragmentInteractionListener , PickPowerFragment.pickPowerInteractionListener {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_hero_me)
val manager : FragmentManager = fragmentManager
var fragment : Fragment? = manager.findFragmentById(R.id.ReplaceFrame)
if (fragment == null){
fragment = MainFragment()
manager.beginTransaction().add(R.id.ReplaceFrame,fragment).commit()
}
}
fun loadPickPowerScreen(){
var pickpowerfrag = PickPowerFragment()
fragmentManager.beginTransaction().replace(R.id.ReplaceFrame, pickpowerfrag).addToBackStack(null).commit()
}
override fun onMainFragmentInteraction(uri: Uri) {
}
override fun onPickPowerInteraction(uri: Uri) {
}
}
这里我从 MainFragment 调用函数 loadPickPowerScreen()
我测试了按钮（我用来将 MainFragment 替换为 pickPowerFragment 的按钮）是否正常工作，方法是在单击按钮时使用它来修改其上的文本，并且它似乎工作得很好。所以我猜那里MainFragment.kt 应该没有问题
这是 MainFragment.kt 中的 onClick() 方法
var onClick = View.OnClickListener(){view ->
var heroActivity : HeroMe = HeroMe()
heroActivity.loadPickPowerScreen()
}
这里是片段 PickPowerFragment.kt
package com.example.mandar.herome.Fragments
import android.app.Fragment
import android.content.Context
import android.net.Uri
import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import com.example.mandar.herome.R
/**
* A simple [Fragment] subclass.
* Activities that contain this fragment must implement the
* [PickPowerFragment.OnFragmentInteractionListener] interface
* to handle interaction events.
* Use the [PickPowerFragment.newInstance] factory method to
* create an instance of this fragment.
*/
class PickPowerFragment : Fragment() {
// TODO: Rename and change types of parameters
private var mParam1: String? = null
private var mParam2: String? = null
private var mListener: pickPowerInteractionListener? = null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
if (arguments != null) {
mParam1 = arguments.getString(ARG_PARAM1)
mParam2 = arguments.getString(ARG_PARAM2)
}
}
override fun onCreateView(inflater: LayoutInflater?, container: ViewGroup?,
savedInstanceState: Bundle?): View? {
val view = inflater!!.inflate(R.layout.fragment_pick_power, container, false)
// Inflate the layout for this fragment
return view
}
// TODO: Rename method, update argument and hook method into UI event
fun onButtonPressed(uri: Uri) {
if (mListener != null) {
mListener!!.onPickPowerInteraction(uri)
}
}
override fun onAttach(context: Context?) {
super.onAttach(context)
if (context is pickPowerInteractionListener) {
mListener = context
} else {
throw RuntimeException(context!!.toString() + " must implement OnFragmentInteractionListener")
}
}
override fun onDetach() {
super.onDetach()
mListener = null
}
/**
* This interface must be implemented by activities that contain this
* fragment to allow an interaction in this fragment to be communicated
* to the activity and potentially other fragments contained in that
* activity.
*
*
* See the Android Training lesson [Communicating with Other Fragments](http://developer.android.com/training/basics/fragments/communicating.html) for more information.
*/
interface pickPowerInteractionListener {
// TODO: Update argument type and name
fun onPickPowerInteraction(uri: Uri)
}
companion object {
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private val ARG_PARAM1 = "param1"
private val ARG_PARAM2 = "param2"
/**
* 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 PickPowerFragment.
*/
// TODO: Rename and change types and number of parameters
fun newInstance(param1: String, param2: String): PickPowerFragment {
val fragment = PickPowerFragment()
val args = Bundle()
args.putString(ARG_PARAM1, param1)
args.putString(ARG_PARAM2, param2)
fragment.arguments = args
return fragment
}
}
}// Required empty public constructor
这里我为项目添加了 Git Repository 链接 Git Android Project: HeroMe
【问题讨论】：
-
发布 logcat 或异常。
-
@EmanuelS 我刚刚上传了 logcat。请检查。谢谢
标签： android android-fragments kotlin