FindViewById/Butterknife.findById仅在API上抛出NullPointerException <23

当我试图在onCreate期间在片段中分配LinearLayout变量时，我得到一个NPE。这个错误只发生在API版本< 23（我没有全部尝试过，但尝试过19和16，它们在启动时崩溃了）。在23以上，一切都很完美，我不知道为什么。问题FindViewById/Butterknife.findById仅在API上抛出NullPointerException <23

代码：

public void reset() { 
     layoutHolder = ButterKnife.findById(view, R.id.layoutHolder); 
     //I get the same error using (LinearLayout) view.findViewById(...) 
     if (layoutHolder.getChildCount() > 0) { 
      layoutHolder.removeAllViews(); 
      layouts.clear(); 
      sections.clear(); 
      addSectionToLayout(createSection(1)); 
     } 
}

view在片段的onCreate

@Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, 
          Bundle savedInstanceState) { 
     // Inflate the layout for this fragment 
     view = inflater.inflate(R.layout.fragment_log, container, false); 
     //Omitted for brevity 
     Butterknife.bind(this, view); 
     return view; 
    }

错误/ stracktrace

E/AndroidRuntime: FATAL EXCEPTION: main 
Process: com.omitted, PID: 2236 
java.lang.NullPointerException 
at butterknife.ButterKnife.findById(ButterKnife.java:343) 
at com.omitted.LogFragment.reset(LogFragment.java:156) 
at com.omitted.LogPresenter.reset(LogPresenter.java:35) 
at com.omitted.CalculatorModel.doReset(CalculatorModel.java:251) 
at com.omitted.CalculatorPresenter.onResetClicked(CalculatorPresenter.java:107) 
at com.omitted.CalculatorFragment.reset(CalculatorFragment.java:130) 
at com.omitted.CalculatorFragment.onCreateView(CalculatorFragment.java:97) 
at android.support.v4.app.Fragment.performCreateView(Fragment.java:1974) 
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1067) 
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1252) 
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:742) 
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1617) 
at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:570) 
at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:141) 
at android.support.v4.view.ViewPager.populate(ViewPager.java:1177) 
at android.support.v4.view.ViewPager.populate(ViewPager.java:1025) 
at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1545) 
at android.view.View.measure(View.java:16497) 
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125) 
at android.support.design.widget.CoordinatorLayout.onMeasureChild(CoordinatorLayout.java:668) 
at android.support.design.widget.CoordinatorLayout.onMeasure(CoordinatorLayout.java:735) 
at android.view.View.measure(View.java:16497) 
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125) 
at android.widget.FrameLayout.onMeasure(FrameLayout.java:310) 
at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:135) 
at android.view.View.measure(View.java:16497) 
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125) 
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1404) 
at android.widget.LinearLayout.measureVertical(LinearLayout.java:695) 
at android.widget.LinearLayout.onMeasure(LinearLayout.java:588) 
at android.view.View.measure(View.java:16497) 
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125) 
at android.widget.FrameLayout.onMeasure(FrameLayout.java:310) 
at android.view.View.measure(View.java:16497) 
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125) 
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1404) 
at android.widget.LinearLayout.measureVertical(LinearLayout.java:695) 
at android.widget.LinearLayout.onMeasure(LinearLayout.java:588) 
at android.view.View.measure(View.java:16497) 
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125) 
at android.widget.FrameLayout.onMeasure(FrameLayout.java:310) 
at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2291) 
at android.view.View.measure(View.java:16497) 
at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1916) 
at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1113) 
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1295) 
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1000) 
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5670) 
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:761) 
at android.view.Choreographer.doCallbacks(Choreographer.java:574) 
at android.view.Choreographer.doFrame(Choreographer.java:544) 
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:747) 
at android.os.Handler.handleCallback(Handler.java:733) 
at android.os.Handler.dispatchMessage(Handler.java:95) 
at android.os.Looper.loop(Looper.java:136) 
t android.app.ActivityThE/AndroidRuntime: FATAL EXCEPTION: main 
ess: com.omitted, PID: 2236 
.lang.NullPointerException 
at butterknife.ButterKnife.findById(ButterKnife.java:343) 
at com.omitted.LogFragment.reset(LogFragment.java:156) 
at com.omitted.LogPresenter.reset(LogPresenter.java:35) 
at com.omitted.CalculatorModel.doReset(CalculatorModel.java:251) 
at com.omitted.CalculatorPresenter.onResetClicked(CalculatorPresenter.java:107) 
at com.omitted.CalculatorFragment.reset(CalculatorFragment.java:130) 
at com.omitted.CalculatorFragment.onCreateView(CalculatorFragment.java:97) 
at android.support.v4.app.Fragment.performCreateView(Fragment.java:1974) 
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1067) 
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1252) 
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:742) 
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1617) 
at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:570) 
at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:141) 
at android.support.v4.view.ViewPager.populate(ViewPager.java:1177) 
at android.support.v4.view.ViewPager.populate(ViewPager.java:1025) 
at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1545) 
at android.view.View.measure(View.java:16497) 
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125) 
at android.support.design.widget.CoordinatorLayout.onMeasureChild(CoordinatorLayout.java:668) 
at android.support.design.widget.CoordinatorLayout.onMeasure(CoordinatorLayout.java:735) 
at android.view.View.measure(View.java:16497) 
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125) 
at android.widget.FrameLayout.onMeasure(FrameLayout.java:310) 
at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:135) 
at android.view.View.measure(View.java:16497) 
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125) 
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1404) 
at android.widget.LinearLayout.measureVertical(LinearLayout.java:695) 
at android.widget.LinearLayout.onMeasure(LinearLayout.java:588) 
at android.view.View.measure(View.java:16497) 
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125) 
at android.widget.FrameLayout.onMeasure(FrameLayout.java:310) 
at android.view.View.measure(View.java:16497) 
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125) 
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1404) 
at android.widget.LinearLayout.measureVertical(LinearLayout.java:695) 
at android.widget.LinearLayout.onMeasure(LinearLayout.java:588) 
at android.view.View.measure(View.java:16497) 
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125) 
at android.widget.FrameLayout.onMeasure(FrameLayout.java:310) 
at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2291) 
at android.view.View.measure(View.java:16497) 
at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1916) 
at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1113) 
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1295) 
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1000) 
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5670) 
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:761) 
at android.view.Choreographer.doCallbacks(Choreographer.java:574) 
at android.view.Choreographer.doFrame(Choreographer.java:544) 
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:747) 
at android.os.Handler.handleCallback(Handler.java:733) 
at android.os.Handler.dispatchMessage(Handler.java:95) 
at android.os.Looper.loop(Looper.java:136) 
at android.app.ActivityTh

我似乎无法想出解决办法初始化。有没有人遇到过这个问题？片段生命周期在API < 23上有所不同吗？

任何输入表示赞赏，谢谢。

来源

2016-08-01 William Smith

用'if（view！= null）'围绕在该方法中的代码解决了这个问题，但是这看起来非常非常黑客。为什么这是必要的？ –

您是否使用ButterKnife.bind（this，view）？

@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 
     View view = inflater.inflate(R.layout.fragment_log, container, false); 
     ButterKnife.bind(this, view); 
     // TODO Use fields... 
     return view; 
}

来源

2016-08-01 04:21:32

是的，我做到了。然而，似乎'ButterKnife.bind（this，view）'在我的片段中工作。我不知道为什么，尤其是因为它在我的其他片段中工作得很好（2个带有制表符的片段布局） –

您可以在活动中附加初始化片段的代码吗？ –

FindViewById/Butterknife.findById仅在API上抛出NullPointerException <23

回答

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