I am learning how to use fragments. I have three instances of Fragment
that are initialized at the top of the class. I am adding the fragment to an activity like this:
Declaring and initializing:
Fragment A = new AFragment();
Fragment B = new BFragment();
Fragment C = new CFragment();
Replacing/Adding:
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.replace(R.id.content_frame, A);
ft.addToBackStack(null);
ft.commit();
These snippets are working properly. Every fragment is attached to the activity, and is saved to the back stack without any problem.
So when I launch A
, C
, and then B
, the stack looks like this:
| |
|B|
|C|
|A|
___
And when I press the 'back' button, B
is destroyed and C
is resumed.
But, when I launch fragment A
a second time, instead of resuming from back stack, it is added at the top of the back stack
| |
|A|
|C|
|A|
___
But I want to resume A
and destroy all fragments on top of it (if any). Actually, I just like the default back stack behavior.
How do I accomplish this?
Expected: (A
should be resumed and top fragments should be destroyed)
| |
| |
| |
|A|
___
Edit: (suggested by A--C)
This is my trying code:
private void selectItem(int position) {
Fragment problemSearch = null, problemStatistics = null;
FragmentManager manager = getSupportFragmentManager();
FragmentTransaction ft = manager.beginTransaction();
String backStateName = null;
Fragment fragmentName = null;
boolean fragmentPopped = false;
switch (position) {
case 0:
fragmentName = profile;
break;
case 1:
fragmentName = submissionStatistics;
break;
case 2:
fragmentName = solvedProblemLevel;
break;
case 3:
fragmentName = latestSubmissions;
break;
case 4:
fragmentName = CPExercise;
break;
case 5:
Bundle bundle = new Bundle();
bundle.putInt("problem_no", problemNo);
problemSearch = new ProblemWebView();
problemSearch.setArguments(bundle);
fragmentName = problemSearch;
break;
case 6:
fragmentName = rankList;
break;
case 7:
fragmentName = liveSubmissions;
break;
case 8:
Bundle bundles = new Bundle();
bundles.putInt("problem_no", problemNo);
problemStatistics = new ProblemStatistics();
problemStatistics.setArguments(bundles);
fragmentName = problemStatistics;
default:
break;
}
backStateName = fragmentName.getClass().getName();
fragmentPopped = manager.popBackStackImmediate(backStateName, 0);
if (!fragmentPopped) {
ft.replace(R.id.content_frame, fragmentName);
}
ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
ft.addToBackStack(backStateName);
ft.commit();
// I am using drawer layout
mDrawerList.setItemChecked(position, true);
setTitle(title[position]);
mDrawerLayout.closeDrawer(mDrawerList);
}
The problem is, when I launch A
and then B
, then press 'back', B
is removed and A
is resumed. and pressing 'back' a second time should exit the app. But it is showing a blank window and I have to press back a third time to close it.
Also, when I launch A
, then B
, then C
, then B
again...
Expected:
| |
| |
|B|
|A|
___
Actual:
| |
|B|
|B|
|A|
___
Should I override onBackPressed()
with any customization or am I missing something?
This question is related to
android
android-fragments
back-stack
I know this is quite late to answer this question but I resolved this problem by myself and thought worth sharing it with everyone.`
public void replaceFragment(BaseFragment fragment) {
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
final FragmentManager fManager = getSupportFragmentManager();
BaseFragment fragm = (BaseFragment) fManager.findFragmentByTag(fragment.getFragmentTag());
transaction.setCustomAnimations(R.anim.enter_from_right, R.anim.exit_to_left, R.anim.enter_from_left, R.anim.exit_to_right);
if (fragm == null) { //here fragment is not available in the stack
transaction.replace(R.id.container, fragment, fragment.getFragmentTag());
transaction.addToBackStack(fragment.getFragmentTag());
} else {
//fragment was found in the stack , now we can reuse the fragment
// please do not add in back stack else it will add transaction in back stack
transaction.replace(R.id.container, fragm, fragm.getFragmentTag());
}
transaction.commit();
}
And in the onBackPressed()
@Override
public void onBackPressed() {
if(getSupportFragmentManager().getBackStackEntryCount()>1){
super.onBackPressed();
}else{
finish();
}
}
Easier solution will be changing this line
ft.replace(R.id.content_frame, A);
to ft.add(R.id.content_frame, A);
And inside your XML layout please use
android:background="@color/white"
android:clickable="true"
android:focusable="true"
Clickable
means that it can be clicked by a pointer device or be tapped by a touch device.
Focusable
means that it can gain the focus from an input device like a keyboard. Input devices like keyboards cannot decide which view to send its input events to based on the inputs itself, so they send them to the view that has focus.
I think this method my solve your problem:
public static void attachFragment ( int fragmentHolderLayoutId, Fragment fragment, Context context, String tag ) {
FragmentManager manager = ( (AppCompatActivity) context ).getSupportFragmentManager ();
FragmentTransaction ft = manager.beginTransaction ();
if (manager.findFragmentByTag ( tag ) == null) { // No fragment in backStack with same tag..
ft.add ( fragmentHolderLayoutId, fragment, tag );
ft.addToBackStack ( tag );
ft.commit ();
}
else {
ft.show ( manager.findFragmentByTag ( tag ) ).commit ();
}
}
which was originally posted in This Question
Step 1: Implement an interface with your activity class
public class AuthenticatedMainActivity extends Activity implements FragmentManager.OnBackStackChangedListener{
@Override
protected void onCreate(Bundle savedInstanceState) {
.............
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.beginTransaction().add(R.id.frame_container,fragment, "First").addToBackStack(null).commit();
}
private void switchFragment(Fragment fragment){
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.beginTransaction()
.replace(R.id.frame_container, fragment).addToBackStack("Tag").commit();
}
@Override
public void onBackStackChanged() {
FragmentManager fragmentManager = getFragmentManager();
System.out.println("@Class: SummaryUser : onBackStackChanged "
+ fragmentManager.getBackStackEntryCount());
int count = fragmentManager.getBackStackEntryCount();
// when a fragment come from another the status will be zero
if(count == 0){
System.out.println("again loading user data");
// reload the page if user saved the profile data
if(!objPublicDelegate.checkNetworkStatus()){
objPublicDelegate.showAlertDialog("Warning"
, "Please check your internet connection");
}else {
objLoadingDialog.show("Refreshing data...");
mNetworkMaster.runUserSummaryAsync();
}
// IMPORTANT: remove the current fragment from stack to avoid new instance
fragmentManager.removeOnBackStackChangedListener(this);
}// end if
}
}
Step 2: When you call the another fragment add this method:
String backStateName = this.getClass().getName();
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.addOnBackStackChangedListener(this);
Fragment fragmentGraph = new GraphFragment();
Bundle bundle = new Bundle();
bundle.putString("graphTag", view.getTag().toString());
fragmentGraph.setArguments(bundle);
fragmentManager.beginTransaction()
.replace(R.id.content_frame, fragmentGraph)
.addToBackStack(backStateName)
.commit();
getFragmentManager().addOnBackStackChangedListener(new FragmentManager.OnBackStackChangedListener() {
@Override
public void onBackStackChanged() {
if(getFragmentManager().getBackStackEntryCount()==0) {
onResume();
}
}
});
Source: Stackoverflow.com