0
我有一個ListFragment，它爲其元素提供了一個ContextMenu。當我把這個片段放入xml-layout時，一切正常，但是當我通過FragmentManager以編程的方式添加這個ListFragment時，這隻能工作到第一次屏幕旋轉。旋轉屏幕後，我可以在Android的復古ListFragment並創建由於當編程添加片段時，ContextMenu不起作用
CustomListFragment fragment = new CustomListFragment();
fragmentTransaction.add(R.id.customFragmentContainer, fragment);
，其中新ListFragment被創建一個新的調試器看到的。當我長按一個項目打開ContextMenu時，新的ListFragment的onCreateContextMenu方法被調用並且結果被傳遞給舊的ListFragment的onContextItemSelected方法。
我覺得它變得更清晰，當我張貼一些代碼：
這裏是我的ListFragment：
public class CustomListFragment extends ListFragment {
private LayoutInflater layoutInflater;
private OnSelectedListener<String> selectionListener;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
layoutInflater = inflater;
return inflater.inflate(R.layout.list_fragment_layout, null);
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
setListAdapter(new CustomListAdapter());
registerForContextMenu(getListView());
}
public void setOnSelectedListener(OnSelectedListener<String> listener) {
selectionListener = listener;
}
private static final String item0 = "item0";
private static final String item1 = "item1";
@Override
public void onCreateContextMenu (ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo) {
menu.add(0, 0, 0, item0);
menu.add(0, 1, 0, item1);
}
@Override
public boolean onContextItemSelected(MenuItem menuItem) {
String selection;
if (menuItem.getItemId()==0)
selection = item0;
else
selection = item1;
if (selectionListener!=null)
selectionListener.onSelected(selection);
return true;
}
private class CustomListAdapter extends BaseAdapter {
private List<String> elemente = new ArrayList<String>();
public CustomListAdapter() {
elemente.add("one");
elemente.add("two");
elemente.add("three");
}
@Override
public int getCount() {
return elemente.size();
}
@Override
public Object getItem(int position) {
return elemente.get(position);
}
@Override
public long getItemId(int position) {
return 0;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
if (convertView==null)
convertView = layoutInflater.inflate(R.layout.element, null);
TextView tv = (TextView)convertView;
tv.setText(elemente.get(position));
return tv;
}
}
}
有了這個活動它正常工作：
public class CustomFragmentActivity extends FragmentActivity implements OnSelectedListener<String> {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.fragment_layout);
FragmentManager fragmentManager = getSupportFragmentManager();
CustomListFragment fragment = (CustomListFragment)fragmentManager.findFragmentById(R.id.customFragment);
fragment.setOnSelectedListener(this);
}
@Override
public void onSelected(String selection) {
Toast.makeText(this, selection, Toast.LENGTH_LONG).show();
}
}
但與此活動它僅在第一個屏幕旋轉之前起作用：
public class CustomFragmentContainerActivity extends FragmentActivity implements OnSelectedListener<String> {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.fragment_container_layout);
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
CustomListFragment fragment = new CustomListFragment();
fragmentTransaction.add(R.id.customFragmentContainer, fragment);
fragmentTransaction.commit();
fragment.setOnSelectedListener(this);
}
@Override
public void onSelected(String selection) {
Toast.makeText(this, selection, Toast.LENGTH_LONG).show();
}
}
OnSelectedListener只是提供一種公共方法的接口。在屏幕旋轉後，結果（所選項目）被傳遞給舊的ListFragment。但是這個舊的ListFragment是由Android系統重新創建的，而selectionListener爲null，所以沒有任何反應。界面看起來像這樣：
public interface OnSelectedListener<V> {
public void onSelected(V selection);
}
最後，也許我應該提到我使用的是v4支持庫。