Question

我从我的Android应用程序中获得以下异常：

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，例外没有引用我的代码。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，我的应用程序中没有抛出此异常。在我升级到Android Studio 2.1.3之后，它才刚刚出现。

其他人似乎也有类似的问题：Fragment must be a public static class to be properly recreated from instance state 但是，我无法在那里找到解决方案。

Answer 1

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 退房：Fragment must be a public static class to be properly recreated from instance state

Answer 2

不确定但是你应该使用public static void onPageSelected（int position）。试一试!!

Android IllegalStateException：Fragment null必须是从实例状态

2 个答案: