Controlling Back Button Inside Fragment

I have programming experience, but not much in Android. I think, on any platform, we can not allow the user leave the screen without the data is saved. We also have to ensure that

Solution 1:

Best practice is to save the data whenever the user navigates away from that screen, regardless of whether the data pass validation or not. This may mean you have to save it in a special way, as an incomplete form or record.

Then, give the user a button (such as a "done" action button) to finally confirm the form entry is complete. Validate the data at this point. If you don't do this, and you drop the incomplete data as you suggest, the user won't be able to switch to another app to look up data they may need to enter in the form.

A good example is in the Gmail application. If you are composing an email and navigate away from that screen (e.g. to look at some other data), it doesn't warn you that it's going to lose your data, it just saves your email as a draft. This happens even if your email is missing mandatory data (the to address). You can switch back and forth as many times as you like until the email is complete.

You don't need to hook the back button specifically in order to do this: you can just save the data in onPause, and probably Toast the user to reassure them you've done it. "Committing" the data (sending the email, or applying the form changes) should remove the draft data, and this is just a normal button onClick.

Since the "design" pages on the Android Developer site shifted to being about "Material Design", they don't seem to have their UX tips any more, but "Never lose my stuff" used to be one of the key principles. I also found the Gmail example in the WayBackMachine's archive of the design pages.

Solution 2:

F3 is called by F2 when the user wants to enter data in the database. F3 has several EditTexts and other views, so that would not be a good idea to leave F3 without alerting the user that he may lose everything.

Have you considered backing up any data inside onPause() (or onDestroy() even) of your Fragment? You can then store any information inside your EditText (perhaps to SharedPreferences), and then restore it when your Fragment restarts if it is destroyed.

That aside, you could create an interface (i.e. BackPressObserver) and have any Fragment you want to react to back presses implement it.

publicinterfaceBackPressObserver {

    boolean isReadyToInterceptBackPress();
    voidonBackPress();

}

Fragment One

publicclassFragmentOneextendsFragmentimplementsBackPressObserver {

    @OverridepublicbooleanisReadyToInterceptBackPress() {
        returnthis.isVisible() && 
            //**Another condition, i.e. !editText.getText().toString().isEmpty();**
    }

    @OverridepublicvoidonBackPress() {
        //Do whatever needs to be done on a back press. When finished, make sure isReadyToInterceptBackPress() will return false.
    }

}

Activity

publicclassMainActivityextendsAppCompatActivity {

    @OverridepublicvoidonBackPressed() {

        for (Fragment fragment : getSupportFragmentManager().getFragments()) {
            if (fragment instanceof BackPressObserver) {
                BackPressObserverobserver= (BackPressObserver) fragment;
                if (observer.isReadyToInterceptBackPress()) {
                    observer.onBackPress();
                    return;
                }
            }
        }

        super.onBackPressed();

    }

}

Solution 3:

You can try this. Inside your activity you can check which fragment is currently showing. If it is the one you want, do your intended action.

Inside your activity put

@OverridepublicvoidonBackPressed() {
FragmentcurrentFragment= getActivity().getFragmentManager().findFragmentById(R.id.fragment_container);

   if (currentFragment instanceof"NAME OF YOUR FRAGMENT CLASS") {
      //Do what you wantreturn;
   }
   //Otherwise, react normallysuper.onBackPressed();
}

You could also try adding this to your Fragment. It is simply adding a keylistener

getView().setOnKeyListener( newOnKeyListener()
{
    @OverridepublicbooleanonKey( View v, int keyCode, KeyEvent event )
    {
        if( keyCode == KeyEvent.KEYCODE_BACK )
        {
            returntrue;
        }
        returnfalse;
    }
} );

Let me know if this works!