当时为了防止Fragment被重复初始化，就选择使用单例模式，但是当使用ViewPager时会出现错误，将单例模式禁用掉后一切正常了。这里简单记录一下。
/** * 单例模式: http://coolshell.cn/articles/265.html */PRivate volatile static SingletonFragment singleton = null;public static SingletonFragment getInstance(int index) { if (singleton== null) { synchronized (SingletonFragment.class) { if (singleton== null) { singleton= new SingletonFragment(); } } } return singleton;}W/dalvikvm: threadid=1: thread exiting with uncaught exception (group=0x415b2930)W/System.err: java.lang.NullPointerExceptionW/System.err: at android.app.Fragment.instantiate(Fragment.java:582)W/System.err: at android.app.FragmentState.instantiate(Fragment.java:97)W/System.err: at android.app.FragmentManagerImpl.restoreAllState(FragmentManager.java:1747)W/System.err: at android.app.Fragment.performCreate(Fragment.java:1684)W/System.err: at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:854)W/System.err: at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1057)W/System.err: at android.app.BackStackRecord.run(BackStackRecord.java:682)W/System.err: at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1435)W/System.err: at android.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:474)W/System.err: at android.support.v13.app.FragmentStatePagerAdapter.finishUpdate(FragmentStatePagerAdapter.java:176)W/System.err: at android.support.v4.view.ViewPager.populate(ViewPager.java:1268)W/System.err: at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:668)W/System.err: at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:630)W/System.err: at android.support.v4.view.ViewPager.setCurrentItem(ViewPager.java:611)W/System.err: at net.duohuo.activity.MyActivity$4.handleMessage(MyActivity.java:239)W/System.err: at android.os.Handler.dispatchMessage(Handler.java:99)W/System.err: at android.os.Looper.loop(Looper.java:137)W/System.err: at android.app.ActivityThread.main(ActivityThread.java:5041)W/System.err: at java.lang.reflect.Method.invokeNative(Native Method)W/System.err: at java.lang.reflect.Method.invoke(Method.java:511)W/System.err: at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)W/System.err: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)W/System.err: at dalvik.system.NativeStart.main(Native Method)新闻热点
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