如何获得嵌套片段中的活动? [英] How to get the Activity in nested fragments?
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问题描述
我试图在ViewPager包含的片段中获取调用getActivity()的活动，而此ViewPager包含在Fragment中.我需要在这些片段中从此活动中调用一些方法，但getActivity始终为该片段返回NULL.
I'm trying to get the activity calling getActivity() in the fragments contained in a ViewPager and this ViewPager is contained inside a Fragment. I need to call some methods from this activity in those fragments but the getActivity is always returning NULL for this fragments.
我不知道这是否是一种好方法，但是我需要视图分页器中包含的片段根据操作栏操作来更新其内容，并显示消息已完成或有错误.
I don't know if this is a good approach but I need the fragments contained by the view pager to update their contents based on action bar actions and display messages saying is done or there was an error.
在此方面的帮助将不胜感激.
Help with this would be greatly appreciated.
这是代码:
内部片段:
public class ReportSessionsFragment extends ReportPageFragment implements IUpdateView {
private static final String TAG = ReportSessionsFragment.class.getSimpleName();
private Sessions fSessions;
private List<Report> reportList = null;
private ReportsAdapter adapter = null;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return super.onCreateView(inflater, container, savedInstanceState);
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
settings = ((BaseActivity)getActivity()).settings;
}
@Override
public void onStart() {
super.onStart();
setCounter(db.getSessionsCount());
if(settings.getSelectedRoom() != null){
reportList = db.getSessionsByRoom(settings.getSelectedRoom().getName(),
settings.getStatusSelectedList());
adapter = new ReportsAdapter(getActivity(), reportList, EReport.Sessions);
mRecyclerView.setAdapter(adapter);
}
}
@Override
public void onStop() {
super.onStop();
}
@Override
public void reload() {
HashMap<String, Object> parameters = new HashMap<>();
parameters.put(Fetcher.REQUEST_PARAMETERS, getEventInformation());
showProgress(getString(R.string.txt_requesting_sessions));
fSessions = new Sessions(getActivity(), this);
fSessions.handleSession(parameters, false);
}
@Override
public void delta() {
}
@Override
public void updateProcess(String message) {
}
@Override
public void onProcessEnded(RequestType type, boolean isProvisioningCompleted, String message) {
reportList = db.getSessionsByRoom(settings.getSelectedRoom().getName(),
settings.getStatusSelectedList());
adapter.notifyDataSetChanged();
hideProgress();
}
@Override
public void onError(Exception e, boolean isProvisioningCompleted) {
hideProgress();
showError(getString(R.string.txt_error_title),
e.getMessage());
}
}
包含ViewPager的片段:
public class ReportSessionsFragment extends ReportPageFragment implements IUpdateView {
private static final String TAG = ReportSessionsFragment.class.getSimpleName();
private Sessions fSessions;
private List<Report> reportList = null;
private ReportsAdapter adapter = null;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return super.onCreateView(inflater, container, savedInstanceState);
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
settings = ((BaseActivity)getActivity()).settings;
}
@Override
public void onStart() {
super.onStart();
setCounter(db.getSessionsCount());
if(settings.getSelectedRoom() != null){
reportList = db.getSessionsByRoom(settings.getSelectedRoom().getName(),
settings.getStatusSelectedList());
adapter = new ReportsAdapter(getActivity(), reportList, EReport.Sessions);
mRecyclerView.setAdapter(adapter);
}
}
@Override
public void onStop() {
super.onStop();
}
@Override
public void reload() {
HashMap<String, Object> parameters = new HashMap<>();
parameters.put(Fetcher.REQUEST_PARAMETERS, getEventInformation());
showProgress(getString(R.string.txt_requesting_sessions));
fSessions = new Sessions(getActivity(), this);
fSessions.handleSession(parameters, false);
}
@Override
public void delta() {
}
@Override
public void updateProcess(String message) {
}
@Override
public void onProcessEnded(RequestType type, boolean isProvisioningCompleted, String message) {
reportList = db.getSessionsByRoom(settings.getSelectedRoom().getName(),
settings.getStatusSelectedList());
adapter.notifyDataSetChanged();
hideProgress();
}
@Override
public void onError(Exception e, boolean isProvisioningCompleted) {
hideProgress();
showError(getString(R.string.txt_error_title),
e.getMessage());
}
}
活动:
public class ReportsActivity extends BaseActivity implements IReports {
private static final String TAG = ReportsActivity.class.getSimpleName();
private ReportsFragment reportFragment;
private HashMap<Integer, MenuItem> menuReports;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
reportFragment = new ReportsFragment();
addFragment(reportFragment);
}
@Override
protected void onStart() {
super.onStart();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.menu_reports, menu);
menuReports = new HashMap<>();
for(int index = 0; index < menu.size(); index++ ){
MenuItem mi = menu.getItem(index);
menuReports.put(mi.getItemId(), mi);
}
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
ReportPageFragment reportPage = (ReportPageFragment)reportFragment.getCurrentReportPage();
switch (item.getItemId()){
case R.id.action_reload:
reportPage.reload();
break;
case R.id.action_delta:
reportPage.delta();
break;
}
return true;
}
@Override
public void displayOptionsByReport(int position) {
MenuItem miReload = null;
if(menuReports != null){
miReload = (MenuItem) menuReports.get(R.id.action_reload);
}
switch (position){
case REPORT_SESSION:
miReload.setVisible(true);
break;
case REPORT_ENROLLMENT:
miReload.setVisible(true);
break;
case REPORT_REGISTRANTS:
miReload.setVisible(false);
break;
case REPORT_ASSOCIATIONS:
miReload.setVisible(false);
break;
}
}
}
FragmentPagerAdapter:
public class ReportsPagerAdapter extends FragmentStatePagerAdapter {
private Context ctx;
public ReportsPagerAdapter(Context ctx, FragmentManager fm) {
super(fm);
this.ctx = ctx;
}
@Override
public Fragment getItem(int position) {
Fragment fragment = null;
switch (position){
case 0:
fragment = Fragment.instantiate(ctx, ReportSessionsFragment.class.getName());
break;
case 1:
fragment = Fragment.instantiate(ctx, ReportEnrollmentFragment.class.getName());
break;
case 2:
fragment = Fragment.instantiate(ctx, ReportRegistrantsFragment.class.getName());
break;
case 3:
fragment = Fragment.instantiate(ctx, ReportAssociationsFragment.class.getName());
break;
}
return fragment;
}
@Override
public int getCount() {
String[] reportListNames = ctx.getResources().getStringArray(R.array.reports);
return reportListNames.length;
}
@Override
public CharSequence getPageTitle(int position) {
String[] reportListNames = ctx.getResources().getStringArray(R.array.reports);
return reportListNames[position];
}
}
推荐答案
每个片段，即使是另一个片段的子片段，在将它们添加到片段树时也会收到对onAttach()的调用.包含片段的活动将作为参数传递.最简单的解决方案是将活动另存为片段的成员.然后可以在以后需要时使用.
Every fragment, even those that are childen of another fragment, receive a call to onAttach() when they are added to the fragment tree. The activity containing the fragment is passed in as a parameter. The simplest solution is may be to save the activity as a member of your fragment. Then it is available when needed later.
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
//save the activity to a member of this fragment
mHostActivity = activity;
}
对于始终在树中固定深度的片段，一种替代方法是根据需要使用getParent()多次，以到达最上面的片段.例如，在您的分页片段的子片段中:
An alternative, for a fragment that is always at a fixed depth in the tree, is to use getParent() as many times as needed to get to the top-most fragment. For example, in your fragments that are children of the pager fragment:
getParentFragment().getActivity()
这篇关于如何获得嵌套片段中的活动?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
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