Question

我的应用有一个带有tabBar的fragmentActivity，可控制视图寻呼机并包含3个片段，当我更新User中的课程fragmentB时，我需要在fragmentC中显示它。我的问题是每次添加新用户时如何刷新fragmentC。

在我写这个问题之前，我尝试了这个问题的所有解决方案：

1。Update ViewPager dynamically?

2。refresh fragment at reload

3。Update Fragment from ViewPager

4。ViewPager PagerAdapter not updating the View

5。How to update fragment content from activity (viewpager)?

这是我的代码

FragmentActivity：

public class MainActivityTab extends FragmentActivity  {


    public SectionsPagerAdapter mSectionsPagerAdapter;
    public ViewPager mViewPager;
    public static MainActivityTab instance = null;


    public static MainActivityTab getInstance(){
        return instance;
    }

    @Override
    protected void onCreate(final Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main_tab);
        getWindow().setStatusBarColor(Color.rgb(191,76,12));
        mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
        mViewPager = (ViewPager) findViewById(R.id.container);
        mViewPager.setAdapter(mSectionsPagerAdapter);
        final TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
        tabLayout.setupWithViewPager(mViewPager);
        tabLayout.getTabAt(0).setIcon(R.drawable.icon_A);
        tabLayout.getTabAt(1).setIcon(R.drawable.icon_B);
        tabLayout.getTabAt(2).setIcon(R.drawable.icon_C);
        mViewPager.setCurrentItem(1,false);
    }

FragmentStatePagerAdapter：

 public class SectionsPagerAdapter extends FragmentStatePagerAdapter {

        public SectionsPagerAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int position) {
            switch (position){
                case 0:
                    return FragmentA.newInstance();
                case 1:
                    return FragmentA.newInstance();
                case 2:
                    return FragmentC.newInstance();
                default:
                    return null;
            }
        }

        @Override
        public int getItemPosition(Object object) {
            return POSITION_NONE;
        }

        @Override
        public int getCount() {
            return 3;
        }

        @Override
        public CharSequence getPageTitle(int position) {
            return null;
        }
    }

FragmentB：

public class FragmentB extends Fragment {

    EditText name;
    EditText age;
    Button btnSave;

    public static FragmentB newInstance() {
        FragmentB fragment = new FragmentB();
        return fragment;
    }
    public FragmentB() {}

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_new2, container, false);
        name = (EditText) rootView.findViewById(R.id.name);
        age = (EditText) rootView.findViewById(R.id.age);
        btnSave = (Button) rootView.findViewById(R.id.btnSave);
        btnSave.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                UserManager.getInstance().creteUser(name.getText().toString(),age.getText().toString());
            }
        });
        return rootView;
    }
}

FragmentC：

public class FragmentC extends Fragment {
    TextView nameTxt;
    TextView ageTxt;

    public static FragmentC newInstance(){
        FragmentC instance = new FragmentC();
        return instance;
    }
    public FragmentC(){

    }
@Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
     View rootView = inflater.inflate(R.layout.fragment_new3, container, false);
    nameTxt = (TextView) rootView.findViewById(R.id.nameTxt);
    ageTxt = (TextView) rootView.findViewById(R.id.ageTxt);
    showUser();
    return rootView;
    }
    public void showUser(){

        if(UserManager.getInstance().getUser().getName()!=null){
            nameTxt.setText(UserManager.getInstance().getUser().getName().toString());
            ageTxt.setText(UserManager.getInstance().getUser().getAge().toString());
        }
    }

}

Answer 1

你可以创建一个回调，如：

public interface UserChangedCallback{
  void onUserChanged();
}

并在要访问用户的每个视图/片段上实现此回调：

@Override
public void onUserChanged() {
  adapter.notifyDataSetChanged();
  // or if you don't have an adapter refresh your textfields or whatever you want
}

通过UserManager.getInstance().registerCallback(this)在用户管理器上注册回调。在内部，用户管理器必须将回调添加到内部列表。

在用户管理器中创建一个私有函数：

private void notifyCallbacks() {
  for(UserChangedCallback callback : registeredCallbacks) {
    callback.onUserChanged();
  } 
}

如果添加/修改/删除用户，则必须始终调用此功能。例如：

public void addUser(User user) {
  users.add(user);
  notifiCallbacks();
}

现在每个视图都会被通知并刷新。

重要！

不要忘记从onDestroy()上的用户管理器取消注册回调，以避免内存泄漏。

Answer 2

找到解决方案：

我在方法onPageSelected中使用，当位置为2时，我的片段分离，然后附加片段。工作得很好！

mViewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
                @Override
                public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

                }

                @Override
                public void onPageSelected(int position) {
                    if(position==2){
                        FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction().add(R.id.fragmant_new3, FragmentC.newInstance());
                        fragmentTransaction.detach(FragmentC.newInstance());
                        fragmentTransaction.attach(FragmentC.newInstance());
                        fragmentTransaction.commit();

                    }
                }

                @Override
                public void onPageScrollStateChanged(int state) {

                }
            });

在FragmentActivity中刷新片段

2 个答案: