Navigation between fragments using backstack and static fabric pattern
suggest changeFirst of all, we need to add our first Fragment
at the beginning, we should do it in the onCreate()
method of our Activity:
if (null == savedInstanceState) {
getSupportFragmentManager().beginTransaction()
.addToBackStack("fragmentA")
.replace(R.id.container, FragmentA.newInstance(), "fragmentA")
.commit();
}
Next, we need to manage our backstack. The easiest way is using a function added in our activity that is used for all FragmentTransactions.
public void replaceFragment(Fragment fragment, String tag) {
//Get current fragment placed in container
Fragment currentFragment = getSupportFragmentManager().findFragmentById(R.id.container);
//Prevent adding same fragment on top
if (currentFragment.getClass() == fragment.getClass()) {
return;
}
//If fragment is already on stack, we can pop back stack to prevent stack infinite growth
if (getSupportFragmentManager().findFragmentByTag(tag) != null) {
getSupportFragmentManager().popBackStack(tag, FragmentManager.POP_BACK_STACK_INCLUSIVE);
}
//Otherwise, just replace fragment
getSupportFragmentManager()
.beginTransaction()
.addToBackStack(tag)
.replace(R.id.container, fragment, tag)
.commit();
}
Finally, we should override onBackPressed()
to exit the application when going back from the last Fragment available in the backstack.
@Override
public void onBackPressed() {
int fragmentsInStack = getSupportFragmentManager().getBackStackEntryCount();
if (fragmentsInStack > 1) { // If we have more than one fragment, pop back stack
getSupportFragmentManager().popBackStack();
} else if (fragmentsInStack == 1) { // Finish activity, if only one fragment left, to prevent leaving empty screen
finish();
} else {
super.onBackPressed();
}
}
Execution in activity:
replaceFragment(FragmentB.newInstance(), "fragmentB");
Execution outside activity (assuming MainActivity
is our activity):
((MainActivity) getActivity()).replaceFragment(FragmentB.newInstance(), "fragmentB");
Found a mistake? Have a question or improvement idea?
Let me know.
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