Hi!
I remember the pain with fragments and the back stack while working on an
app last year. My solution was the following. In the activity's onCreate
method I would do the following:
FragmentManager fm = getSupportFragmentManager();
> fm.addOnBackStackChangedListener(new OnBackStackChangedListener() {
> @Override
> public void onBackStackChanged() {
> FragmentManager fm = getSupportFragmentManager();
>
> if(fm.getBackStackEntryCount() == 0) {
> finish();
> }
> }
> });
>
It basically listens to fragment back stack changes and forces the Activity
to finish when the stack is empty
On Sunday, August 4, 2013 4:47:47 AM UTC-5, user123 wrote:
>
> Im trying to implement a fragment based navigation pattern, which can be
> reduced to this:
>
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> In words: There is:
>
> -
>
> Home fragment
> -
>
> Fragment A
> -
>
> Fragment B
>
> The fragments are shown in FrameLayout "content". The navigation bar is
> part of the activity.
>
> Workflow should be: Press back on home: Exit App. Press back on A or B:
> show Home.
>
> Most of it works as it should, but I have the problem that with a complex
> workflow like this:
>
> Start(home) - A - B - A - Back - B - Back
>
> I expect that it will show home, but instead it shows A. I think it's
> because the first transaction (home - A) it's in the backstack and it shows
> A. But I don't understand why then it works correctly in the simple cases?
>
> The code:
>
> public class MainActivity extends FragmentActivity {
> boolean isInHome; //a flag to control when we add fragment to the backstack
> or not
> @Overrideprotected void onCreate(Bundle savedInstanceState) {
> super.onCreate(savedInstanceState);
> setContentView(R.layout.activity_main);
>
> //set home fragment programmatically first time
> FragmentTransaction transaction =
> getSupportFragmentManager().beginTransaction();
> Fragment fragmentHome = new FragmentHome();
> transaction.replace(R.id.content, fragmentHome);
> transaction.commit();
>
> isInHome = true;
>
> //initialize layout
> Button home = (Button) findViewById(R.id.home);
> Button a = (Button) findViewById(R.id.a);
> Button b = (Button) findViewById(R.id.b);
>
> home.setOnClickListener(new View.OnClickListener() {
> @Override
> public void onClick(View v) {
> //clear complete backstack (in this case, just pop home
> transaction)
> getSupportFragmentManager().popBackStackImmediate(null,
> FragmentManager.POP_BACK_STACK_INCLUSIVE);
>
> //show home fragment
> FragmentTransaction transaction =
> getSupportFragmentManager().beginTransaction();
> Fragment fragmentHome = new FragmentHome();
> transaction.replace(R.id.content, fragmentHome);
> transaction.commit();
>
> isInHome = true;
> }
> });
>
> a.setOnClickListener(new View.OnClickListener() {
> @Override
> public void onClick(View v) {
> FragmentTransaction transaction =
> getSupportFragmentManager().beginTransaction();
> Fragment fragmentA = new FragmentA();
> transaction.replace(R.id.content, fragmentA);
> if (isInHome) { //add the home transaction to the backstack, such
> that press back on this fragment shows home again
> transaction.addToBackStack("home");
> }
> transaction.commit();
> isInHome = false;
> }
> });
>
> b.setOnClickListener(new View.OnClickListener() {
> @Override
> public void onClick(View v) {
> FragmentTransaction transaction =
> getSupportFragmentManager().beginTransaction();
> Fragment fragmentB = new FragmentB();
> transaction.replace(R.id.content, fragmentB);
> if (isInHome) { //add the home transaction to the backstack, such
> that press back on this fragment shows home again
> transaction.addToBackStack("home");
> }
> transaction.commit();
> isInHome = false;
> }
> });}
> @Overridepublic void onBackPressed() {
> super.onBackPressed();
>
> isInHome = true; //quick solution to update status - when press back on A
> or B, we are in home (and press back in home exits the app, so this doesn't
> matter)}
>
> }
>
> What's wrong here?
>
> Thanks in advance.
>
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