使用View参数从片段调用活动方法

Question

在我的一个片段中，我在其onCreate（）方法中调用以下内容：

   ((MainActivity)getActivity()).nextPage(view);

这是我的MainActivity中的功能：

    // To 2nd page from 1st
    public void nextPage(View view) {
            mViewPager.setCurrentItem(2);
        }

为什么我不能这样做？我想要做的就是移动到下一个片段而不实际替换视图，因为这会中断我的应用程序的体验。以下是传统方法，但这不适用于我的目的：

NextFragment nextFrag= new NextFragment();
     this.getFragmentManager().beginTransaction()
     .replace(R.id.layout, nextFrag, TAG_FRAGMENT)
     .addToBackStack(null)
     .commit();

我收到以下错误消息：

java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.View.findViewById(int)' on a null object reference
            at com.app.test.TemplateFragment.DrawTemplateWithTransparency(TemplateFragment.java:894)
            at com.app.test.MainActivity.SetupTemplate(MainActivity.java:443)
            at com.app.test.MainActivity.nextPage(MainActivity.java:381)
            at com.app.test.DesignerFragment.handleIncomingIntent(DesignerFragment.java:401)
            at com.app.test.DesignerFragment.onResume(DesignerFragment.java:195)
            at android.support.v4.app.Fragment.performResume(Fragment.java:2005)
            at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1108)
            at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1248)
            at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:738)
            at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1613)
            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:1106)
            at android.support.v4.view.ViewPager.populate(ViewPager.java:952)
            at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1474)
            at android.view.View.measure(View.java:18794)
            at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:715)
            at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:461)
            at android.view.View.measure(View.java:18794)
            at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
            at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
            at android.support.v7.internal.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:124)
            at android.view.View.measure(View.java:18794)
            at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
            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:18794)
            at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
            at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
            at android.view.View.measure(View.java:18794)
            at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
            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:18794)
            at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
            at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
            at com.android.internal.policy.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2643)
            at android.view.View.measure(View.java:18794)
            at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2100)
            at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1216)
            at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1452)
            at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1107)
            at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6013)
            at android.view.Choreographer$CallbackRecord.run(Choreographer.java:858)
            at android.view.Choreographer.doCallbacks(Choreographer.java:670)
            at android.view.Choreographer.doFrame(Choreographer.java:606)
            at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:844)
            at android.os.Handler.handleCallback(Handler.java:739)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:148)
            at android.app.ActivityThread.main(ActivityThread.java:5417)
            at java.lang.reflect.Method.invoke(Native Method)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(Zygo