Question

我有一个ViewPager活动，这个ViewPager包含3个片段。

我正在使用FragmentPagerAdapter创建片段，如下所示：

    class ViewPagerUser(fragmentManager: FragmentManager, private val matchDetails: MatchDetails, private val context: Context) : FragmentPagerAdapter(fragmentManager) {

    // Returns total number of pages
    override fun getCount(): Int {
        return NUM_ITEMS
    }

    // Returns the fragment to display for that page
    override fun getItem(position: Int): Fragment? {
        when (position) {
            0 -> return FragmentDetailMatchInfoUser.newInstance(matchDetails)
            1 -> return FragmentDetailMatchParticipantsUser.newInstance(matchDetails)
            2 -> return FragmentDetailMatchWall.newInstance(matchDetails)
            else -> return null
        }
    }

    // Returns the page title for the top indicator
    override fun getPageTitle(position: Int): CharSequence? {
        when (position) {
            0 -> return context.getString(R.string.info)
            1 -> return context.getString(R.string.player)
            2 -> return context.getString(R.string.wall)
            else -> return null
        }
    }

    companion object {
        private val NUM_ITEMS = 3
    }
}

这是我使用它的方式

    if (matchDetails != null && (matchDetails.cancelled!! || screenType == App.USER || matchDetails.matchStatus == 40 || matchDetails.matchStatus == 50)) {
        adapterViewPager = ViewPagerUser(supportFragmentManager, matchDetails, this)
    } else if (screenType == App.ORGANIZER) {
        adapterViewPager = ViewPagerOrganizer(supportFragmentManager, matchDetails!!, this)
    }

    viewPager?.adapter = adapterViewPager

    viewPager?.offscreenPageLimit = 3

我认为这是在ViewPager中处理Fragments的最佳方式，但是我在Crashlytics上收到了很多关于“已添加片段”的报告，如下所示：

Fatal Exception: java.lang.IllegalStateException: Fragment already added: FragmentDetailMatchInfoUser{b17d64 #0 id=0x7f090551 android:switcher:2131297617:0}
   at android.support.v4.app.FragmentManagerImpl.addFragment(Unknown Source)
   at android.support.v4.app.BackStackRecord.addOp(Unknown Source)
   at android.support.v4.app.FragmentManagerImpl.executeOps(Unknown Source)
   at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(Unknown Source)
   at android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(Unknown Source)
   at android.support.v4.app.FragmentManagerImpl.execSingleAction(Unknown Source)
   at android.support.v4.app.BackStackRecord.commitNowAllowingStateLoss(Unknown Source)
   at android.support.v4.app.FragmentPagerAdapter.finishUpdate(Unknown Source)
   at android.support.v4.view.ViewPager.initViewPager(Unknown Source)
   at android.support.v4.view.ViewPager.populate(Unknown Source)
   at android.support.v4.view.ViewPager.onMeasure(Unknown Source)
   at android.view.View.measure(View.java:19883)
   at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6087)
   at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1464)
   at android.widget.LinearLayout.measureVertical(LinearLayout.java:758)
   at android.widget.LinearLayout.onMeasure(LinearLayout.java:640)
   at android.view.View.measure(View.java:19883)
   at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6087)
   at android.support.design.widget.CoordinatorLayout.onMeasureChild(Unknown Source)
   at android.support.design.widget.HeaderScrollingViewBehavior.onMeasureChild(Unknown Source)
   at android.support.design.widget.AppBarLayout$ScrollingViewBehavior.onMeasureChild(Unknown Source)
   at android.support.design.widget.CoordinatorLayout.onMeasure(Unknown Source)
   at android.view.View.measure(View.java:19883)
   at android.support.constraint.ConstraintLayout.internalMeasureChildren(Unknown Source)
   at android.support.constraint.ConstraintLayout.onMeasure(Unknown Source)
   at android.view.View.measure(View.java:19883)
   at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6087)
   at android.widget.FrameLayout.onMeasure(FrameLayout.java:185)
   at android.view.View.measure(View.java:19883)
   at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6087)
   at android.widget.FrameLayout.onMeasure(FrameLayout.java:185)
   at android.support.v7.widget.ContentFrameLayout.onMeasure(Unknown Source)
   at android.view.View.measure(View.java:19883)
   at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6087)
   at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1464)
   at android.widget.LinearLayout.measureVertical(LinearLayout.java:758)
   at android.widget.LinearLayout.onMeasure(LinearLayout.java:640)
   at android.view.View.measure(View.java:19883)
   at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6087)
   at android.widget.FrameLayout.onMeasure(FrameLayout.java:185)
   at android.view.View.measure(View.java:19883)
   at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6087)
   at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1464)
   at android.widget.LinearLayout.measureVertical(LinearLayout.java:758)
   at android.widget.LinearLayout.onMeasure(LinearLayout.java:640)
   at android.view.View.measure(View.java:19883)
   at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6087)
   at android.widget.FrameLayout.onMeasure(FrameLayout.java:185)
   at com.android.internal.policy.DecorView.onMeasure(DecorView.java:689)
   at android.view.View.measure(View.java:19883)
   at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2293)
   at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1384)
   at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1637)
   at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1272)
   at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6408)
   at android.view.Choreographer$CallbackRecord.run(Choreographer.java:874)
   at android.view.Choreographer.doCallbacks(Choreographer.java:686)
   at android.view.Choreographer.doFrame(Choreographer.java:621)
   at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:860)
   at android.os.Handler.handleCallback(Handler.java:751)
   at android.os.Handler.dispatchMessage(Handler.java:95)
   at android.os.Looper.loop(Looper.java:154)
   at android.app.ActivityThread.main(ActivityThread.java:6165)
   at java.lang.reflect.Method.invoke(Method.java)
   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:888)
   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:778)

我在Stackoverflow中经历了与此问题相关的几乎所有问题，建议的答案无法帮助我...错误总会回来。

我有什么问题吗？

Answer 1

这个报告可能是因为您每次ViewPager要求片段时都在创建片段的新实例。

您应该在创建ViewPager时尝试创建片段实例：

class ViewPagerUser(fragmentManager: FragmentManager, private val matchDetails: MatchDetails, private val context: Context) : FragmentPagerAdapter(fragmentManager) {

private val fragmentDetailMatchInfoUser = FragmentDetailMatchInfoUser.newInstance(matchDetails)
private val fragmentDetailMatchParticipantsUser = FragmentDetailMatchParticipantsUser.newInstance(matchDetails)
private val fragmentDetailMatchWall = FragmentDetailMatchWall.newInstance(matchDetails)

    // Returns total number of page
    override fun getCount(): Int {
        return NUM_ITEMS
    }

    // Returns the fragment to display for that page
    override fun getItem(position: Int): Fragment? {
        when (position) {
            0 -> return fragmentDetailMatchInfoUser
            1 -> return fragmentDetailMatchParticipantsUser
            2 -> return fragmentDetailMatchWall
            else -> return null
        }
    }

    // Returns the page title for the top indicator
    override fun getPageTitle(position: Int): CharSequence? {
        when (position) {
            0 -> return context.getString(R.string.info)
            1 -> return context.getString(R.string.player)
            2 -> return context.getString(R.string.wall)
            else -> return null
        }
    }

    companion object {
        private val NUM_ITEMS = 3
    }
 }

我有类似的问题，它帮助了我。希望它也能帮到你。

Answer 2

使用isAdded()检查片段是否与活动分离。

if(!mFragmentDetailMatchInfoUser.isAdded())
 {
  return FragmentDetailMatchInfoUser.newInstance(matchDetails);
}

以及两个片段。

Answer 3

我遇到了同样的问题，我通过向 FragmentPagerAdapter 添加第二个参数解决了这个问题：

class ViewPagerUser(fragmentManager: FragmentManager, private val matchDetails: MatchDetails, private val context: Context) : FragmentPagerAdapter(fragmentManager, BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT) {...}

更多： FragmentPagerAdapter(fragmentManager) 已弃用，必须改成 FragmentPagerAdapter(fragmentManager, BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT) 问题才能解决。

已经使用FragmentPagerAdapter添加了片段

3 个答案: