ViewPager 中 Fragment 内的 TextView 在方向更改时为空

Question

我在里面有一个MainActivity，我用Fragments 创建了ViewPager。我正在使用 savedInstanceState 存储值以在方向更改后设置TextView。我也想改变价值，例如使用MainActivity 中的按钮。 Button 可以正常工作，但是如果我更改方向，则 Button 无法在 Fragment 中设置 TextView，因为 TextView 现在为空。

MyFragment

public class MyFragment extends Fragment {

    private TextView textView;
    private String info;

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

        View view = inflater.inflate(R.layout.item_weather, container, false);
        textView = view.findViewById(R.id.text_view);
        Bundle bundle = getArguments();
        info = bundle.getString("info");
        setInfo(info);
        return view;

    }

    public void setInfo(String info) {
        this.info = info;
        textView.setText(info); //here is the error
    }
}

在MainActivity.java 在OnCreate

myFragment = new MyFragment();
viewPager = findViewById(R.id.viewpager);
viewPager.setOffscreenPageLimit(10);

List<Fragment> fragments = new ArrayList<>();
fragments.add(myFragment);

pagerAdapter = new MyPageAdapter(getSupportFragmentManager(), fragments);
viewPager.setAdapter(pagerAdapter);

MyPagerAdapter 看起来像这样：

public class MyPageAdapter extends FragmentStatePagerAdapter {

    private List<Fragment> fragments;

    public MyPageAdapter(FragmentManager fm, List<Fragment> fragments) {
        super(fm);
        this.fragments = fragments;
    }

    @Override
    public Fragment getItem(int position) {
        return fragments.get(position);
    }

    @Override
    public int getCount() {
        return fragments.size();
    }
}

正如我所说的一切正常，但如果我使用 Button 进行方向更改后出现错误：

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference

有什么办法解决这个问题吗？

编辑： 完全错误

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.app.myapp, PID: 15400
    java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
        at com.example.app.myapp.fragments.myFragment.setInfo(myFragment.java:53)
        at com.example.app.myapp.MainActivity.onOptionsItemSelected(MainActivity.java:195)
        at android.app.Activity.onMenuItemSelected(Activity.java:3543)
        at android.support.v4.app.FragmentActivity.onMenuItemSelected(FragmentActivity.java:407)
        at android.support.v7.app.AppCompatActivity.onMenuItemSelected(AppCompatActivity.java:195)
        at android.support.v7.view.WindowCallbackWrapper.onMenuItemSelected(WindowCallbackWrapper.java:108)
        at android.support.v7.view.WindowCallbackWrapper.onMenuItemSelected(WindowCallbackWrapper.java:108)
        at android.support.v7.app.ToolbarActionBar$2.onMenuItemClick(ToolbarActionBar.java:63)
        at android.support.v7.widget.Toolbar$1.onMenuItemClick(Toolbar.java:203)
        at android.support.v7.widget.ActionMenuView$MenuBuilderCallback.onMenuItemSelected(ActionMenuView.java:780)
        at android.support.v7.view.menu.MenuBuilder.dispatchMenuItemSelected(MenuBuilder.java:822)
        at android.support.v7.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:171)
        at android.support.v7.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:973)
        at android.support.v7.view.menu.MenuPopup.onItemClick(MenuPopup.java:127)
        at android.widget.AdapterView.performItemClick(AdapterView.java:318)
        at android.widget.AbsListView.performItemClick(AbsListView.java:1159)
        at android.widget.AbsListView$PerformClick.run(AbsListView.java:3136)
        at android.widget.AbsListView$3.run(AbsListView.java:4052)
        at android.os.Handler.handleCallback(Handler.java:873)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:193)
        at android.app.ActivityThread.main(ActivityThread.java:6669)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)

Answer 1

进入fragment尝试在onViewCreated方法上初始化textView：

@Override
public View onViewCreated(view: View, savedInstanceState: Bundle) {

   // Your initialization code here

} 

Answer 2

解决方案：

好的，EpicPandaForce 感谢您的提示。

为了解决这个问题，我在MainActivity中使用了

@Override
    protected void onResume() {
        super.onResume();
        viewPager.setAdapter(pagerAdapter);
    }

    @Override
    protected void onPause() {
        super.onPause();
        viewPager.setAdapter(null);
    }