FragmentContainerView中的問題與解決方法
一、發(fā)現(xiàn)問題
1摔握、錯誤表現(xiàn)
今天在做一個項(xiàng)目的時候央勒, 發(fā)現(xiàn)了一個莫名奇妙的問題。根據(jù)官方的建議蚀乔,使用FragmentContainerView去切換和處理Fragment。
為布局文件中的FragmentContainerView設(shè)置一個開始Fragment菲茬,我稱之為FragmentA吉挣,同時需要FragmentA傳入?yún)?shù)進(jìn)行初始化派撕,然后問題出現(xiàn)了:編譯通過,布局文件沒有任何問題,運(yùn)行時報(bào)錯并退出應(yīng)用睬魂,報(bào)錯指出我的布局文件出問題终吼,同時提示一個用到的參數(shù)為空。
當(dāng)場裂開氯哮,此外我注意到此前我的代碼中FragmentA會被初始化兩次际跪,我注釋掉那個提示為空的參數(shù),一切豁然開朗喉钢。
原來FragmentA被初始化了兩次:第一次初始化是在setContentView
的時候進(jìn)行初始化姆打,此時沒有參數(shù)傳入,導(dǎo)致參數(shù)為空肠虽,導(dǎo)致android.view.InflateException
錯誤幔戏,再導(dǎo)致提示布局文件錯誤。
我想嘗試復(fù)現(xiàn)這個錯誤税课,并嘗試解決這個問題闲延。
2、錯誤日志
--------- beginning of crash
2021-12-07 20:07:43.034 10842-10842/ink.ptlr.nodemusic E/AndroidRuntime: FATAL EXCEPTION: main
Process: ink.ptlr.nodemusic, PID: 10842
java.lang.RuntimeException: Unable to start activity ComponentInfo{ink.ptlr.nodemusic/ink.ptlr.nodemusic.activity.UtilsActivity}: android.view.InflateException: Binary XML file line #18 in ink.ptlr.nodemusic:layout/activity_utils: Binary XML file line #18 in ink.ptlr.nodemusic:layout/activity_utils: Error inflating class androidx.fragment.app.FragmentContainerView
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:4060)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:4247)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:91)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:149)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:103)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2613)
at android.os.Handler.dispatchMessage(Handler.java:110)
at android.os.Looper.loop(Looper.java:219)
at android.app.ActivityThread.main(ActivityThread.java:8668)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:513)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1109)
Caused by: android.view.InflateException: Binary XML file line #18 in ink.ptlr.nodemusic:layout/activity_utils: Binary XML file line #18 in ink.ptlr.nodemusic:layout/activity_utils: Error inflating class androidx.fragment.app.FragmentContainerView
Caused by: android.view.InflateException: Binary XML file line #18 in ink.ptlr.nodemusic:layout/activity_utils: Error inflating class androidx.fragment.app.FragmentContainerView
Caused by: java.lang.NullPointerException
at ink.ptlr.nodemusic.fragment.MusicListFragment.onCreate(MusicListFragment.kt:46)
at androidx.fragment.app.Fragment.performCreate(Fragment.java:2949)
at androidx.fragment.app.FragmentStateManager.create(FragmentStateManager.java:475)
at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:278)
at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:2189)
at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:2106)
at androidx.fragment.app.FragmentManager.execSingleAction(FragmentManager.java:1971)
at androidx.fragment.app.BackStackRecord.commitNowAllowingStateLoss(BackStackRecord.java:311)
at androidx.fragment.app.FragmentContainerView.<init>(FragmentContainerView.java:180)
at androidx.fragment.app.FragmentLayoutInflaterFactory.onCreateView(FragmentLayoutInflaterFactory.java:52)
at androidx.fragment.app.FragmentController.onCreateView(FragmentController.java:135)
at androidx.fragment.app.FragmentActivity.dispatchFragmentsOnCreateView(FragmentActivity.java:319)
at androidx.fragment.app.FragmentActivity.onCreateView(FragmentActivity.java:298)
at android.view.LayoutInflater.tryCreateView(LayoutInflater.java:1079)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:1007)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:971)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:1133)
at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:1094)
at android.view.LayoutInflater.inflate(LayoutInflater.java:692)
at android.view.LayoutInflater.inflate(LayoutInflater.java:536)
at com.android.internal.policy.HwPhoneLayoutInflater.inflate(HwPhoneLayoutInflater.java:138)
at android.view.LayoutInflater.inflate(LayoutInflater.java:483)
at androidx.appcompat.app.AppCompatDelegateImpl.setContentView(AppCompatDelegateImpl.java:699)
at androidx.appcompat.app.AppCompatActivity.setContentView(AppCompatActivity.java:195)
at ink.ptlr.nodemusic.activity.UtilsActivity.onCreate(UtilsActivity.kt:25)
at android.app.Activity.performCreate(Activity.java:8214)
at android.app.Activity.performCreate(Activity.java:8202)
2021-12-07 20:07:43.034 10842-10842/ink.ptlr.nodemusic E/AndroidRuntime: at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1320)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:4033)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:4247)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:91)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:149)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:103)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2613)
at android.os.Handler.dispatchMessage(Handler.java:110)
at android.os.Looper.loop(Looper.java:219)
at android.app.ActivityThread.main(ActivityThread.java:8668)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:513)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1109)
2021-12-07 20:07:43.041 10842-10842/ink.ptlr.nodemusic I/Process: Sending signal. PID: 10842 SIG: 9
二伯复、問題復(fù)現(xiàn)
1慨代、創(chuàng)建項(xiàng)目
新建一個名為FCVT(F
ragmentC
ontainerV
iewT
est)的項(xiàng)目,在下面新建一個MainActivity
和一個TestFragment
邢笙,采用FragmentContainerView
啸如。
結(jié)構(gòu)如下:
【提示】需要以下依賴:
implementation 'androidx.fragment:fragment:1.3.2'
MainActivity
負(fù)責(zé)載入布局文件并初始化Fragment。
- activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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=".MainActivity">
<!-- 動態(tài)加載Fragment -->
<!-- 并設(shè)置起始Fragment為TestFragment -->
<androidx.fragment.app.FragmentContainerView
android:id="@+id/fragmentContainerView"
android:name="ink.ptlr.fcvt.TestFragment"
android:layout_width="0dp"
android:layout_height="0dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
tools:layout="@layout/test_fragment" />
<!-- 報(bào)錯會指向上一行氮惯,但實(shí)際上這個布局文件沒有任何問題 -->
</androidx.constraintlayout.widget.ConstraintLayout>
- MainActyvity.kt
package ink.ptlr.fcvt
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
/* 在這里被實(shí)例化一次
* 此時叮雳,沒有傳入數(shù)據(jù)參數(shù),為空妇汗,會導(dǎo)致報(bào)錯
*/
setContentView(R.layout.activity_main)
val transaction = supportFragmentManager.beginTransaction()
for(fragment in supportFragmentManager.fragments){
transaction.remove(fragment)
}
// 第二次被初始化帘不,可正常執(zhí)行
val fcvt: TestFragment = TestFragment.newInstance("Hello FCVT",1024)
transaction.add(fcvt,"FCVT")
transaction.commitNow()
}
}
TestFragment
- test_fragment.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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=".TestFragment">
<!-- 用于顯示信息 -->
<TextView
android:id="@+id/tvMsg"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:textAlignment="center"
android:textSize="20sp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
- TestFragment.kt
package ink.ptlr.fcvt
import android.annotation.SuppressLint
import androidx.lifecycle.ViewModelProvider
import android.os.Bundle
import android.util.Log
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.TextView
private const val KEY_MSG = "MSG"
private const val KEY_NUM = "NUM"
// private var count = 1
class TestFragment : Fragment() {
companion object {
/*這里傳入?yún)?shù)*/
fun newInstance(msg: String, num: Int) = TestFragment().apply {
arguments = Bundle().apply {
putString(KEY_MSG,msg)
putInt(KEY_NUM, num)
}
}
}
private lateinit var viewModel: TestViewModel
private var msg: String? = null
private var num: Int? = null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
/*獲取參數(shù)*/
arguments?.let {
msg = it.getString(KEY_MSG)
num = it.getInt(KEY_NUM)
}
/*此時不能使用參數(shù)num,否則會報(bào)錯*/
var result = num!!.plus(1)
Log.i("FCVT","MSG: $msg, NUM: ${num}")
//count++
}
@SuppressLint("SetTextI18n")
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
val rootView:View = inflater.inflate(R.layout.test_fragment, container, false)
val tvMsg: TextView = rootView.findViewById(R.id.tvMsg)
tvMsg.text = "MSG: $msg, NUM: $num"
return rootView
}
override fun onActivityCreated(savedInstanceState: Bundle?) {
super.onActivityCreated(savedInstanceState)
viewModel = ViewModelProvider(this).get(TestViewModel::class.java)
// TODO: Use the ViewModel
}
}
2、編譯運(yùn)行于報(bào)錯
上面的代碼可以通過編譯杨箭,但運(yùn)行時應(yīng)用閃退寞焙,報(bào)錯日志如下:
--------- beginning of crash
2021-12-08 12:48:10.344 31676-31676/? E/AndroidRuntime: FATAL EXCEPTION: main
Process: ink.ptlr.fcvt, PID: 31676
java.lang.RuntimeException: Unable to start activity ComponentInfo{ink.ptlr.fcvt/ink.ptlr.fcvt.MainActivity}: android.view.InflateException: Binary XML file line #19 in ink.ptlr.fcvt:layout/activity_main: Binary XML file line #19 in ink.ptlr.fcvt:layout/activity_main: Error inflating class androidx.fragment.app.FragmentContainerView
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:4060)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:4247)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:91)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:149)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:103)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2613)
at android.os.Handler.dispatchMessage(Handler.java:110)
at android.os.Looper.loop(Looper.java:219)
at android.app.ActivityThread.main(ActivityThread.java:8668)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:513)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1109)
Caused by: android.view.InflateException: Binary XML file line #19 in ink.ptlr.fcvt:layout/activity_main: Binary XML file line #19 in ink.ptlr.fcvt:layout/activity_main: Error inflating class androidx.fragment.app.FragmentContainerView
Caused by: android.view.InflateException: Binary XML file line #19 in ink.ptlr.fcvt:layout/activity_main: Error inflating class androidx.fragment.app.FragmentContainerView
Caused by: java.lang.NullPointerException
at ink.ptlr.fcvt.TestFragment.onCreate(TestFragment.kt:39)
at androidx.fragment.app.Fragment.performCreate(Fragment.java:2949)
at androidx.fragment.app.FragmentStateManager.create(FragmentStateManager.java:475)
at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:278)
at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:2189)
at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:2106)
at androidx.fragment.app.FragmentManager.execSingleAction(FragmentManager.java:1971)
at androidx.fragment.app.BackStackRecord.commitNowAllowingStateLoss(BackStackRecord.java:311)
at androidx.fragment.app.FragmentContainerView.<init>(FragmentContainerView.java:176)
at androidx.fragment.app.FragmentLayoutInflaterFactory.onCreateView(FragmentLayoutInflaterFactory.java:52)
at androidx.fragment.app.FragmentController.onCreateView(FragmentController.java:135)
at androidx.fragment.app.FragmentActivity.dispatchFragmentsOnCreateView(FragmentActivity.java:319)
at androidx.fragment.app.FragmentActivity.onCreateView(FragmentActivity.java:298)
at android.view.LayoutInflater.tryCreateView(LayoutInflater.java:1079)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:1007)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:971)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:1133)
at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:1094)
at android.view.LayoutInflater.inflate(LayoutInflater.java:692)
at android.view.LayoutInflater.inflate(LayoutInflater.java:536)
at com.android.internal.policy.HwPhoneLayoutInflater.inflate(HwPhoneLayoutInflater.java:138)
at android.view.LayoutInflater.inflate(LayoutInflater.java:483)
at androidx.appcompat.app.AppCompatDelegateImpl.setContentView(AppCompatDelegateImpl.java:696)
at androidx.appcompat.app.AppCompatActivity.setContentView(AppCompatActivity.java:170)
at ink.ptlr.fcvt.MainActivity.onCreate(MainActivity.kt:12)
at android.app.Activity.performCreate(Activity.java:8214)
at android.app.Activity.performCreate(Activity.java:8202)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1320)
2021-12-08 12:48:10.344 31676-31676/? E/AndroidRuntime: at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:4033)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:4247)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:91)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:149)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:103)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2613)
at android.os.Handler.dispatchMessage(Handler.java:110)
at android.os.Looper.loop(Looper.java:219)
at android.app.ActivityThread.main(ActivityThread.java:8668)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:513)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1109)
三、錯誤分析
這個問題困擾了我佷久互婿,因?yàn)槌霈F(xiàn)了不止一次捣郊,而且每次都困擾了我很久。
仔細(xì)分析后發(fā)現(xiàn)了問題所在:
在setContentView
時TestFragment會被實(shí)例化慈参,此時需要自定義的參數(shù)是沒有初始化的呛牲,不能使用。
在代碼中:
/*此時不能使用參數(shù)num,否則會報(bào)錯*/
var result = num!!.plus(1)
我使用!!
告訴編譯器這個數(shù)據(jù)不為空驮配,于是編譯通過娘扩,但實(shí)際情況是這個數(shù)據(jù)會出現(xiàn)為空的情況着茸,于是在運(yùn)行的時候出現(xiàn)了錯誤。
錯誤的原因:在上述項(xiàng)目中琐旁,TesTFragment會被初始化兩次涮阔,第一次是setContentView的時候,第二次是調(diào)用TestFragment.instance(msg: String, num: Int)的時候旋膳。
四澎语、解決方法
思路:在創(chuàng)建時傳入?yún)?shù)或只實(shí)例化一次
需求不能變,在初始化時傳入?yún)?shù)是要求验懊,在仔細(xì)閱讀官方文檔Fragment 管理器 | Android 開發(fā)者 | Android Developers (google.cn)后擅羞,通過自定義FragmentFactory
解決問題(創(chuàng)建時傳入?yún)?shù))。
修改后:
TestFragment.kt
package ink.ptlr.fcvt
import android.annotation.SuppressLint
import androidx.lifecycle.ViewModelProvider
import android.os.Bundle
import android.util.Log
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.TextView
import androidx.fragment.app.FragmentFactory
private const val KEY_MSG = "MSG"
private const val KEY_NUM = "NUM"
// private var count = 1
class TestFragment() : Fragment() {
companion object {
/*這里傳入?yún)?shù)*/
fun newInstance(msg: String, num: Int) = TestFragment().apply {
arguments = Bundle().apply {
putString(KEY_MSG,msg)
putInt(KEY_NUM, num)
}
}
}
private lateinit var viewModel: TestViewModel
private var msg: String? = null
private var num: Int? = null
init {
msg = "Init By default"
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
/*獲取參數(shù)*/
arguments?.let {
msg = it.getString(KEY_MSG)
num = it.getInt(KEY_NUM)
}
/*此時不能使用參數(shù)num,否則會報(bào)錯*/
//var result = num!!.plus(1)
Log.i("FCVT","MSG: $msg, NUM: ${num}")
//count++
}
@SuppressLint("SetTextI18n")
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
Log.i("FCVT","OCV")
var rootView:View = inflater.inflate(R.layout.test_fragment, container, false)
val tvMsg: TextView = rootView.findViewById(R.id.tvMsg)
tvMsg.text = "MSG: $msg, NUM: $num"
return rootView
}
override fun onActivityCreated(savedInstanceState: Bundle?) {
super.onActivityCreated(savedInstanceState)
viewModel = ViewModelProvider(this).get(TestViewModel::class.java)
// TODO: Use the ViewModel
}
// 自定義的FragmentFactory义图,內(nèi)部類
class MyFactory(var msg: String, var num: Int): FragmentFactory(){
override fun instantiate(classLoader: ClassLoader, className: String): Fragment =
when(loadFragmentClass(classLoader, className)){
TestFragment::class.java -> newInstance(msg, num)
else -> super.instantiate(classLoader, className)
}
}
}
MainActivity.kt
package ink.ptlr.fcvt
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
// 使用自定義的FragmentFactory,必須在super.onCreate()之前
supportFragmentManager.fragmentFactory = TestFragment.MyFactory("HELLO FCVT",1024)
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
}
}
五减俏、總結(jié)
這個問題是我偷懶,鬼官方太過信任碱工,使用官方模板和不熟悉安卓開發(fā)導(dǎo)致的娃承,此外,此處還有一個添加Fragment時會出現(xiàn)空白的問題怕篷,今后需要解決历筝。
PS: 發(fā)現(xiàn)并解決這個問題內(nèi)心十分喜悅,希望能把這種喜悅分享給大家廊谓,并對大家有一定幫助梳猪。