Android IllegalStateException：Fragment null必须是要从实例状态正确重新创建的公共静态类
我从我的Android应用程序中得到以下exception：
FATAL EXCEPTION: main java.lang.IllegalStateException: Fragment null must be a public static class to be properly recreated from instance state. at android.support.v4.app.BackStackRecord.doAddOp(BackStackRecord.java:435) at android.support.v4.app.BackStackRecord.add(BackStackRecord.java:420) at android.support.v4.app.FragmentStatePagerAdapter.instantiateItem(FragmentStatePagerAdapter.java:123) at android.support.v4.view.ViewPager.addNewItem(ViewPager.java:1006) at android.support.v4.view.ViewPager.populate(ViewPager.java:1154) at android.support.v4.view.ViewPager.populate(ViewPager.java:1088) at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1614) at android.view.View.measure(View.java:15525) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4825) 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:15525) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4825) 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:15525) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4825) at android.support.v7.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:389) at android.view.View.measure(View.java:15525) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4825) at android.widget.FrameLayout.onMeasure(FrameLayout.java:310) at android.view.View.measure(View.java:15525) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4825) 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:15525) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4825) at android.widget.FrameLayout.onMeasure(FrameLayout.java:310) at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2438) at android.view.View.measure(View.java:15525) at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1874) at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1089) at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1265) at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:989) at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4351) at android.view.Choreographer$CallbackRecord.run(Choreographer.java:749) at android.view.Choreographer.doCallbacks(Choreographer.java:562) at android.view.Choreographer.doFrame(Choreographer.java:532) at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735) at android.os.Handler.handleCallback(Handler.java:725) at android.os.Handler.dispatchMessage(Handler.java:92) at android.os.Looper.loop(Looper.java:137) at android.app.ActivityThread.main(ActivityThread.java:5227) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:511) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:795) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:562) at dalvik.system.NativeStart.main(Native Method) 不幸的是，该exception没有引用我的代码。 一旦我开始一个包含碎片的活动，它就会出现。 我认为以下是我的代码的相关部分：
public class MonthViewActivity extends AppCompatActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_month); getSupportActionBar().setDisplayHomeAsUpEnabled(true); final ViewPager viewPager = (ViewPager) findViewById(R.id.pager); viewPager.setAdapter(new FragmentStatePagerAdapter(getSupportFragmentManager()) { @Override public Fragment getItem(final int position) { return new Fragment() { @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { View rootView = inflater.inflate(R.layout.month_view, container, false); return rootView; } }; } @Override public int getCount() { return 12; } }); viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() { @Override public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) { } @Override public void onPageSelected(int position) { Month month = Year.getCurrent().getMonth(position); TextView month_name = (TextView) findViewById(R.id.month_name); month_name.setText(month.getName()); } @Override public void onPageScrollStateChanged(int state) { } }); viewPager.setCurrentItem(getIntent().getExtras().getInt("month")); if (getIntent().getExtras().getInt("month") == 0) { // The OnPageChangeListener doesn't do it for the first one Month month = Year.getCurrent().getMonth(0); TextView month_name = (TextView) findViewById(R.id.month_name); month_name.setText(month.getName()); } } }
当我使用Android Studio 1.5.1时，我的应用程序没有抛出此exception。 我刚刚升级到Android Studio 2.1.3后就出现了。
其他人似乎有类似的问题： 片段必须是一个公共静态类才能从实例状态中正确地重新创建但是，我找不到解决方案。
不确定，但你应该使用public static void onPageSelected（int position）。 试一试!!
android支持lib 24.2.0及以上版本的问题我们可以使用android支持lib 23.0.0检查： Fragment必须是一个公共静态类才能从实例状态中正确地重新创建