Question

我的项目崩溃并显示从活动切换到片段时出现以下错误。

08-12 20:00:56.835    1711-1711/com.facebooklogin E/AndroidRuntime﹕ FATAL EXCEPTION: main
    java.lang.NullPointerException
            at info.fastbadmainton2.slidingmenu.NewsFragment.onCreateView(NewsFragment.java:66)
            at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:829)
            at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1035)
            at android.app.BackStackRecord.run(BackStackRecord.java:635)
            at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1397)
            at android.app.FragmentManagerImpl$1.run(FragmentManager.java:426)
            at android.os.Handler.handleCallback(Handler.java:615)
            at android.os.Handler.dispatchMessage(Handler.java:92)
            at android.os.Looper.loop(Looper.java:153)
            at android.app.ActivityThread.main(ActivityThread.java:5086)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:821)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:584)
            at dalvik.system.NativeStart.main(Native Method)

它在声明中显示错误 -

actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_STANDARD);

为什么它在这个语句中显示错误？我的应用程序没有崩溃，如果我删除这个语句但我的片段变得透明，这样活动可见后面。为什么我的片段becoms透明？

活动

public class NewsPopup extends FragmentActivity {
    TextView tv1,tv2,tv3;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.newspopup);
        Configuration config = getResources().getConfiguration();

        FragmentManager fragmentManager = getFragmentManager();
        final FragmentTransaction fragmentTransaction =
                fragmentManager.beginTransaction();

        tv1=(TextView)findViewById(R.id.textView21);
        tv1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Fragment newFragment = new NewsFragment();
                fragmentTransaction.replace(android.R.id.content, newFragment);
                fragmentTransaction.commit();
            }
        });
        tv2=(TextView)findViewById(R.id.textView22);
        tv2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent i=new Intent();
                i.setClass(getApplicationContext(), NewsPopup2.class);
                startActivity(i);
            }
        });
        tv3=(TextView)findViewById(R.id.textView24);
        tv3.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent i=new Intent();
                i.setClass(getApplicationContext(), NewsPopup3.class);
                startActivity(i);
            }
        });

    }
}

片段

public class NewsFragment extends Fragment   {
    private FragmentActivity myContext;
    private ViewPager viewPager;
    private TabsPagerAdapter2 mAdapter;
    ActionBar actionBar;
     private String[] tabs = { "My Teams", "All Teams", "Trending" };
    public NewsFragment(){}
    @Override
    public void onAttach(Activity activity) {
        myContext=(FragmentActivity) activity;
        super.onAttach(activity);
    }


    public void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setHasOptionsMenu(true);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {

        View rootView = inflater.inflate(R.layout.news, container, false);


        actionBar = getActivity().getActionBar();
      actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_STANDARD);
        TextView tv=(TextView)rootView.findViewById(R.id.textView11);

        tv.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent i=new Intent();
                i.setClass(myContext, NewsPopup.class);
                startActivity(i);
            }
        });

        TextView tv1=(TextView)rootView.findViewById(R.id.textView13);

        tv1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent i=new Intent();
                i.setClass(myContext, NewsPopup2.class);
                startActivity(i);
            }
        });

        TextView tv2=(TextView)rootView.findViewById(R.id.textView43);

        tv2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent i=new Intent();
                i.setClass(myContext, NewsPopup3.class);
                startActivity(i);
            }
        });
        return rootView;
    }
    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle item selection
        switch (item.getItemId()) {
            case R.id.action_search2:
                // recordVideo();
                //countClick++;
                Intent i = new Intent();
                i.setClass(myContext, LeagueSelect2.class);
                startActivity(i);
                return true;

            default:
                return super.onOptionsItemSelected(item);
        }
    }
    /*@Override
    public void onTabSelected(Tab tab, FragmentTransaction ft) {
        // TODO Auto-generated method stub
        viewPager.setCurrentItem(tab.getPosition());
    }

    @Override
    public void onTabUnselected(Tab tab, FragmentTransaction ft) {
        // TODO Auto-generated method stub

    }

    @Override
    public void onTabReselected(Tab tab, FragmentTransaction ft) {
        // TODO Auto-generated method stub

    }*/
}

Answer 1

您可能正在使用支持片段。但是您的活动扩展了FragmentActivity。 getActionBar（）在旧设备上返回null，因为它们没有任何操作栏。让您的活动从appcompat库扩展ActionBarActivity，然后调用

actionBar = ((ActionBarActivity) getActivity()).getActionBar();

在onCreateView中从活动移动到fragment-NullPointer异常

1 个答案: