所以我在使用带有FragmentStatePagerAdapter的ViewPager时遇到这个问题然后我试图选择当前页面(即向用户显示第二页而不是第一页),我不时会得到这个例外.
问题似乎是并发性,因为viewpager仍在添加/初始化片段,即当我正在尝试设置当前页面时正在运行片段事务.像这样的东西:
pagerAdapter = new MyFragmentPagerAdapter(getChildFragmentManager()); viewPager.setAdapter(pagerAdapter); pagerAdapter.addItems(...) //Addings ID's here for each fragment,this is where the adapter notifies the viewpager viewPager.setCurrentItem(1); //This is where the two transactions at the same time might happen
问题是:我怎么知道viewpager什么时候完成片段初始化所以设置当前页面是安全的?
确切的例外是:
Fatal Exception: java.lang.IllegalStateException: FragmentManager is already executing transactions at android.support.v4.app.FragmentManagerImpl.execSingleAction(FragmentManager.java:1631) at android.support.v4.app.BackStackRecord.commitNowAllowingStateLoss(BackStackRecord.java:679) at android.support.v4.app.FragmentStatePagerAdapter.finishUpdate(FragmentStatePagerAdapter.java:166) at android.support.v4.view.ViewPager.populate(ViewPager.java:1272) at android.support.v4.view.ViewPager.populate(ViewPager.java:1120) at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1646) at android.view.View.measure(View.java:18916) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5972) at android.support.design.widget.CoordinatorLayout.onMeasureChild(CoordinatorLayout.java:703) at android.support.design.widget.HeaderScrollingViewBehavior.onMeasureChild(HeaderScrollingViewBehavior.java:90) at android.support.design.widget.AppBarLayout$ScrollingViewBehavior.onMeasureChild(AppBarLayout.java:1367) at android.support.design.widget.CoordinatorLayout.onMeasure(CoordinatorLayout.java:768) at android.view.View.measure(View.java:18916) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5972) at android.widget.FrameLayout.onMeasure(FrameLayout.java:194) at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:139) at android.view.View.measure(View.java:18916) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5972) at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1465) at android.widget.LinearLayout.measureVertical(LinearLayout.java:748) at android.widget.LinearLayout.onMeasure(LinearLayout.java:630) at android.view.View.measure(View.java:18916) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5972) at android.widget.FrameLayout.onMeasure(FrameLayout.java:194) at android.view.View.measure(View.java:18916) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5972) at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1465) at android.widget.LinearLayout.measureVertical(LinearLayout.java:748) at android.widget.LinearLayout.onMeasure(LinearLayout.java:630) at android.view.View.measure(View.java:18916) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5972) at android.widget.FrameLayout.onMeasure(FrameLayout.java:194) at com.android.internal.policy.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2693) at android.view.View.measure(View.java:18916) at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2231) at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1307) at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1549) at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1198) at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6268) at android.view.Choreographer$CallbackRecord.run(Choreographer.java:873) at android.view.Choreographer.doCallbacks(Choreographer.java:676) at android.view.Choreographer.doFrame(Choreographer.java:606) at android.view.Choreographer$FramedisplayEventReceiver.run(Choreographer.java:859) at android.os.Handler.handleCallback(Handler.java:739) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:168) at android.app.ActivityThread.main(ActivityThread.java:5885) at java.lang.reflect.Method.invoke(Method.java) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:797) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:687)
解决方法
Handler handler = new Handler(); handler.post(new Runnable() { @Override public void run() { viewPager.setCurrentItem(1); } });