[英]Android fragment not appearing when list item is clicked
目前,我正在Android中使用Fragments進行實驗,這一步讓我發瘋。 我在一個包含項目(書)列表的片段中有一個ListView。 當我單擊列表中的某個項目時,該片段應換成另一個包含該項目詳細信息的片段。 但是,盡管setOnItemClickListener()方法確實有效,但Fragment並未出現(我已經收到了logcat消息,確認已單擊ListView中的項目。我還將另一個logcat消息放入第二個Fragment的onCreateView()方法中,因此片段似乎已創建但並未被誇大...
這是FFBooksFragment,它是包含項目ListView的Fragment:
package com.example.android.gamebookcollector;
public class FFBooksFragment extends Fragment {
private static final String TAG = "FFBooksFragment";
private Button ffButton;
private CustomListAdapter adapter;
private ListView booksList;
private static final int STANDARD_APPBAR = 0;
private static final int SEARCH_APPBAR = 1;
private int mAppbarState;
private AppBarLayout viewBooksToolbar, searchBar;
@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_ffbooks, container, false);
viewBooksToolbar = (AppBarLayout) view.findViewById(R.id.viewBooksToolbar);
searchBar = (AppBarLayout) view.findViewById(R.id.searchBooksToolbar);
booksList = (ListView) view.findViewById(R.id.booksList);
setUpGamebooksList();
ImageView searchIcon = (ImageView) view.findViewById(R.id.ivSearchIcon);
searchIcon.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Log.d(TAG, "Clicked search icon in standard bar");
toggleToolbarState();
}
});
ImageView ivBackArrow = (ImageView) view.findViewById(R.id.ivBackArrow);
ivBackArrow.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Log.d(TAG, "Clicked back arrow in search bar");
toggleToolbarState();
}
});
return view;
}
private void toggleToolbarState() {
if (mAppbarState==STANDARD_APPBAR) {
setAppbarState(SEARCH_APPBAR);
}else {
setAppbarState(STANDARD_APPBAR);
}
}
private void setAppbarState(int state) {
Log.d(TAG, "Changing app bar state to " + state);
mAppbarState = state;
if(mAppbarState==STANDARD_APPBAR){
searchBar.setVisibility(View.GONE);
viewBooksToolbar.setVisibility(View.VISIBLE);
View view = getView();
InputMethodManager inputMethodManager = (InputMethodManager) getActivity().getSystemService(Context.INPUT_METHOD_SERVICE);
try{
inputMethodManager.hideSoftInputFromWindow(view.getWindowToken(), 0);
}catch(NullPointerException e){
Log.d(TAG, "setAppbar state: Null pointer exception. " + e.getMessage());
}
}
else if (mAppbarState==SEARCH_APPBAR){
viewBooksToolbar.setVisibility(View.GONE);
searchBar.setVisibility(View.VISIBLE);
InputMethodManager inputMethodManager = (InputMethodManager) getActivity().getSystemService(Context.INPUT_METHOD_SERVICE);
inputMethodManager.toggleSoftInput(InputMethodManager.SHOW_FORCED, 0);
}
}
private void setUpGamebooksList(){
final ArrayList<Gamebook> gameBooks = new ArrayList<>();
gameBooks.add(new Gamebook("1. Book title", "Book authors", "Publisher", "Year", R.drawable.image1));
gameBooks.add(new Gamebook("2. Book title", "Book authors", "Publisher", "Year", R.drawable.image2));
gameBooks.add(new Gamebook("3. Book title", "Book authors", "Publisher", "Year", R.drawable.image3));
gameBooks.add(new Gamebook("4. Book title", "Book authors", "Publisher", "Year", R.drawable.image4));
adapter = new CustomListAdapter(getActivity(), R.layout.layout_book_list_item, gameBooks, "drawable://");
/* Now we call the setAdapter() method on our booksList list and pass it our adapter. */
booksList.setAdapter(adapter);
// Set up an onItemClickListener for checking to see if any book in the list is clicked on.
// If so, go to the book fragment (which is blank for now).
booksList.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Log.d(TAG, "Navigating to book fragment...");
BookFragment bookFragment = new BookFragment();
FragmentTransaction fragmentTransaction = getActivity().getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.fragmentContainer, bookFragment);
// adding a string identifier string to the fragment, not really necessary right now but might as well do it
fragmentTransaction.addToBackStack(getString(R.string.book_fragment));
fragmentTransaction.commit();
}
});
}
@Override
public void onResume() {
super.onResume();
setAppbarState(STANDARD_APPBAR);
}
}
這是BooksFragment,當單擊上面Fragment的ListView中的項目時,應該會出現:
package com.example.android.gamebookcollector;
public class BookFragment extends Fragment {
private static final String TAG = "BookFragment";
private android.support.v7.widget.Toolbar toolbar;
@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_book, container, false);
toolbar = (Toolbar) view.findViewById(R.id.booksToolbar);
Log.d(TAG, "Book fragment started...");
// Set up the toolbar
((AppCompatActivity)getActivity()).setSupportActionBar(toolbar);
setHasOptionsMenu(true);
ImageView ivBackArrow = (ImageView) view.findViewById(R.id.ivBackArrow);
ivBackArrow.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Log.d(TAG, "Back arrow clicked");
// pop the previous fragment off the back stack (i.e. navigate back)
getActivity().getSupportFragmentManager().popBackStack();
}
});
/* If the edit button is clicked, go to the edit book fragment */
ImageView ivEdit = (ImageView) view.findViewById(R.id.iv_edit);
ivEdit.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Log.d(TAG, "Clicked the edit button...");
EditBookFragment editBookFragment = new EditBookFragment();
FragmentTransaction fragmentTransaction = getActivity().getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.fragmentContainer, editBookFragment);
// adding a string identifier string to the fragment, not really necessary right now but might as well do it.
// We can retrieve fragments by using their string identifer.
fragmentTransaction.addToBackStack(getString(R.string.edit_book_fragment));
fragmentTransaction.commit();
}
});
return view;
}
@Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
inflater.inflate(R.menu.book_menu, menu);
super.onCreateOptionsMenu(menu, inflater);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.menuitem_delete:
Log.d(TAG, "Delete book...");
break;
default:
break;
}
return super.onOptionsItemSelected(item);
}
}
問題是您在片段返回視圖之前正在執行FindViewById
做這個:
將所有視圖綁定到OnActivityCreated
並檢查片段導入語句
//請導入
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentTransaction;
public class FFBooksFragment extends Fragment { private static final String TAG = "FFBooksFragment"; private Button ffButton; private CustomListAdapter adapter; private ListView booksList; private static final int STANDARD_APPBAR = 0; private static final int SEARCH_APPBAR = 1; private int mAppbarState; private AppBarLayout viewBooksToolbar, searchBar; @Nullable @Override public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) { View view = inflater.inflate(R.layout.fragment_ffbooks, container, false); return view; } @Override public void onActivityCreated(@Nullable Bundle savedInstanceState) { super.onActivityCreated(savedInstanceState); viewBooksToolbar = (AppBarLayout) getActivity().findViewById(R.id.viewBooksToolbar); searchBar = (AppBarLayout) getActivity().findViewById(R.id.searchBooksToolbar); booksList = (ListView) getActivity().findViewById(R.id.booksList); setUpGamebooksList(); ImageView searchIcon = (ImageView) getActivity().findViewById(R.id.ivSearchIcon); searchIcon.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { Log.d(TAG, "Clicked search icon in standard bar"); toggleToolbarState(); } }); ImageView ivBackArrow = (ImageView) getActivity().findViewById(R.id.ivBackArrow); ivBackArrow.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { Log.d(TAG, "Clicked back arrow in search bar"); toggleToolbarState(); } }); } private void toggleToolbarState() { if (mAppbarState==STANDARD_APPBAR) { setAppbarState(SEARCH_APPBAR); }else { setAppbarState(STANDARD_APPBAR); } } private void setAppbarState(int state) { Log.d(TAG, "Changing app bar state to " + state); mAppbarState = state; if(mAppbarState==STANDARD_APPBAR){ searchBar.setVisibility(View.GONE); viewBooksToolbar.setVisibility(View.VISIBLE); View view = getView(); InputMethodManager inputMethodManager = (InputMethodManager) getActivity().getSystemService(Context.INPUT_METHOD_SERVICE); try{ inputMethodManager.hideSoftInputFromWindow(view.getWindowToken(), 0); }catch(NullPointerException e){ Log.d(TAG, "setAppbar state: Null pointer exception. " + e.getMessage()); } } else if (mAppbarState==SEARCH_APPBAR){ viewBooksToolbar.setVisibility(View.GONE); searchBar.setVisibility(View.VISIBLE); InputMethodManager inputMethodManager = (InputMethodManager) getActivity().getSystemService(Context.INPUT_METHOD_SERVICE); inputMethodManager.toggleSoftInput(InputMethodManager.SHOW_FORCED, 0); } } private void setUpGamebooksList(){ final ArrayList<Gamebook> gameBooks = new ArrayList<>(); gameBooks.add(new Gamebook("1. Book title", "Book authors", "Publisher", "Year", R.drawable.image1)); gameBooks.add(new Gamebook("2. Book title", "Book authors", "Publisher", "Year", R.drawable.image2)); gameBooks.add(new Gamebook("3. Book title", "Book authors", "Publisher", "Year", R.drawable.image3)); gameBooks.add(new Gamebook("4. Book title", "Book authors", "Publisher", "Year", R.drawable.image4)); adapter = new CustomListAdapter(getActivity(), R.layout.layout_book_list_item, gameBooks, "drawable://"); /* Now we call the setAdapter() method on our booksList list and pass it our adapter. */ booksList.setAdapter(adapter); // Set up an onItemClickListener for checking to see if any book in the list is clicked on. // If so, go to the book fragment (which is blank for now). booksList.setOnItemClickListener(new AdapterView.OnItemClickListener() { @Override public void onItemClick(AdapterView<?> parent, View view, int position, long id) { Log.d(TAG, "Navigating to book fragment..."); BookFragment bookFragment = new BookFragment(); FragmentTransaction fragmentTransaction = getActivity().getSupportFragmentManager().beginTransaction(); fragmentTransaction.replace(R.id.fragmentContainer, bookFragment); // adding a string identifier string to the fragment, not really necessary right now but might as well do it fragmentTransaction.addToBackStack(getString(R.string.book_fragment)); fragmentTransaction.commit(); } }); } @Override public void onResume() { super.onResume(); setAppbarState(STANDARD_APPBAR); } }
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