我尝试将数据从活动更新为片段，这将是3个小时。我检查了所有页面，但它没有工作......
我必须制作一个BookManager。我已经创建了一些类来完成它。
我有一个带有两个片段的主要活动，第一个是空的，第二个是我的书列表的摘要（书的大部分价格，平均值......）。当我想要添加一本书时，我会使用一个新的活动并在添加书籍（其工作）后重新获取数据。 我想在添加这本书之后刷新片段。
我的主要活动代码：
public class MainActivity extends AppCompatActivity {
/**
* The {@link android.support.v4.view.PagerAdapter} that will provide
* fragments for each of the sections. We use a
* {@link FragmentPagerAdapter} derivative, which will keep every
* loaded fragment in memory. If this becomes too memory intensive, it
* may be best to switch to a
* {@link android.support.v4.app.FragmentStatePagerAdapter}.
*/
private SectionsPagerAdapter mSectionsPagerAdapter;
/**
* The {@link ViewPager} that will host the section contents.
*/
private ViewPager mViewPager;
private SimpleBookManager bookManager;
public final static int ADD_BOOK_REQUEST = 1;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
bookManager = new SimpleBookManager();
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
// Create the adapter that will return a fragment for each of the three
// primary sections of the activity.
mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
// Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) findViewById(R.id.container);
mViewPager.setAdapter(mSectionsPagerAdapter);
TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(mViewPager);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.button_add_menu) {
Intent intent = new Intent(MainActivity.this, AddBookActivity.class);
startActivityForResult(intent, ADD_BOOK_REQUEST);
return true;
}
return super.onOptionsItemSelected(item);
}
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == ADD_BOOK_REQUEST) {
// On vérifie aussi que l'opération s'est bien déroulée
if (resultCode == RESULT_OK) {
// On affiche le bouton qui a été choisi
String[] valueBook = data.getStringArrayExtra("VALUE");
Book book = this.bookManager.createBook();
book.setTitle(valueBook[0]);
book.setAuthor(valueBook[1]);
book.setCourse(valueBook[2]);
book.setIsbm(valueBook[3]);
book.setPrice((int) Integer.parseInt(valueBook[4]));
}
}
}
/**
* A {@link FragmentPagerAdapter} that returns a fragment corresponding to
* one of the sections/tabs/pages.
*/
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
// getItem is called to instantiate the fragment for the given page.
// Return a PlaceholderFragment (defined as a static inner class below).
switch (position) {
case 0:
return PlaceholderFragment.newInstance(position + 1);
case 1:
Fragment frag = SummaryFragment.newInstance(bookManager);
return frag;
}
return PlaceholderFragment.newInstance(position + 1);
}
@Override
public int getCount() {
// Show 2 total pages.
return 2;
}
@Override
public CharSequence getPageTitle(int position) {
switch (position) {
case 0:
return "COLLECTION";
case 1:
return "SUMMARY";
}
return null;
}
}
在onActivityResult的方法中，我添加了这本书，当我回到摘要片段时，我想在这里刷新或者最终。我尝试使用FragmentTransaction，但提交无效，因为我没有标记来获取我的片段（我不知道如何获取片段）。 ..而且我们没有片段的实例，因为我们使用静态方法来创建它。
我的片段代码：
public class SummaryFragment extends Fragment {
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private static final String BOOKMANAGER = "book";
// TODO: Rename and change types of parameters
private String[] info;
private OnFragmentInteractionListener mListener;
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* @return A new instance of fragment SummaryFragment.
*/
// TODO: Rename and change types and number of parameters
public static SummaryFragment newInstance(SimpleBookManager bookManager) {
String[] info = new String[5];
info[0] = String.valueOf(bookManager.count());
info[1] = String.valueOf(bookManager.getTotalCost());
info[2] = String.valueOf(bookManager.getMaxPrice());
info[3] = String.valueOf(bookManager.getMinPrice());
info[4] = String.valueOf(bookManager.getMeanPrice());
SummaryFragment fragment = new SummaryFragment();
Bundle args = new Bundle();
args.putStringArray(BOOKMANAGER, info);
fragment.setArguments(args);
return fragment;
}
public SummaryFragment() {
// Required empty public constructor
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
this.info = getArguments().getStringArray(BOOKMANAGER);
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View rootView;
TextView textView;
rootView = inflater.inflate(R.layout.fragment_summary, container, false);
textView = (TextView) rootView.findViewById(R.id.nbbook_value);
textView.setText(this.info[0]);
textView = (TextView) rootView.findViewById(R.id.totalcost_value);
textView.setText(this.info[1] + " SEK");
textView = (TextView) rootView.findViewById(R.id.mostprice_value);
textView.setText(this.info[2] + " SEK");
textView = (TextView) rootView.findViewById(R.id.leastprice_value);
textView.setText(this.info[3] + " SEK");
textView = (TextView) rootView.findViewById(R.id.averageprice_value);
textView.setText(this.info[4] + " SEK");
return rootView;
}
// TODO: Rename method, update argument and hook method into UI event
public void onButtonPressed(Uri uri) {
if (mListener != null) {
mListener.onFragmentInteraction(uri);
}
}
@Override
public void onAttach(Context context) {
super.onAttach(context);
Activity a;
if (context instanceof Activity){
a=(Activity) context;
}
}
@Override
public void onDetach() {
super.onDetach();
mListener = null;
}
/**
* This interface must be implemented by activities that contain this
* fragment to allow an interaction in this fragment to be communicated
* to the activity and potentially other fragments contained in that
* activity.
* <p/>
* See the Android Training lesson <a href=
* "http://developer.android.com/training/basics/fragments/communicating.html"
* >Communicating with Other Fragments</a> for more information.
*/
public interface OnFragmentInteractionListener {
// TODO: Update argument type and name
public void onFragmentInteraction(Uri uri);
}
}
答案 0 :(得分：0)
您可以通过调用FragmentPagerAdapter的getItem方法获取Fragment实例。
SummaryFragment frag = (SummaryFragment) mSectionsPagerAdapter.getItem(1);
然后调用Fragment实例中的方法刷新显示，确保在Fragment上调用方法之前检查null。
if (frag != null) {
frag.refreshBook(book);
}