androidandroid-fragmentsandroid-actionbar

Reputation: 8034

actionbar up navigation with fragments

I have a tabbed Actionbar/viewpager layout with three tabs say A, B, and C. In tab C tab(fragment),I am adding another fragment say fragment D. with

 DFragment f= new DFragment();
 ft.add(android.R.id.content, f, "");
 ft.remove(CFragment.this);
 ft.addToBackStack(null);
 ft.commit();

I modify actionbar in DFragment's onResume to add up button:

ActionBar ab = getActivity().getActionBar();
ab.setNavigationMode(ActionBar.NAVIGATION_MODE_STANDARD);
ab.setDisplayHomeAsUpEnabled(true);
ab.setDisplayShowHomeEnabled(true);

Now in DFragment, when I press hardware(phone) Back button, I return to the original Tabbed(ABC) layout with CFragment selected. How can I achieve this functionality with actionbar up button?

Upvotes: 94

Answers (10)

Benedict Lang

Reputation: 165

If you want to go back to your previous activity if this activity has an empty stack of fragments:

This could be useful if you have a MainActivity and you are navigating to e.g. a SettingsActivity with nested prefernceScreens. NavigateUp will pop fragments until you can finish the SettingsActivity to go back to parentActivity/root.

/**
 * On actionbar up-button popping fragments from stack until it is empty.
 * @return true if fragment popped or returned to parent activity successfully.
 */
@Override
public boolean onSupportNavigateUp() {
    //Pop back stack if the up button is pressed.
    boolean canGoBack = getSupportFragmentManager().getBackStackEntryCount()>0;
    if (canGoBack) {
        getSupportFragmentManager().popBackStack();
    } else {
        finish();
        return super.onSupportNavigateUp();
    }
    return true;
}

Note: setDisplayHomeAsUpEnabled(true); in fragment activities onCreate()

Upvotes: 0

SohailAziz

Reputation: 8034

I got it. just override onOptionsItemSelected in hosting activity and popup the backstack, e.g.

public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
        case android.R.id.home: {
            FragmentManager fm = getSupportFragmentManager();
            if (fm.getBackStackEntryCount() > 0) {
                fm.popBackStack();
                return true;
            }
            break;
        }
    }
    return super.onOptionsItemSelected(item);
}

Call getActionBar().setDisplayHomeAsUpEnabled(boolean); and getActionBar().setHomeButtonEnabled(boolean); in onBackStackChanged() as explained in an answer below.

Upvotes: 43

Roger Garzon Nieto

Reputation: 6594

Implement OnBackStackChangedListener and add this code to your Fragment Activity.

@Override
public void onCreate(Bundle savedInstanceState) {
    //Listen for changes in the back stack
    getSupportFragmentManager().addOnBackStackChangedListener(this);
    //Handle when activity is recreated like on orientation Change
    shouldDisplayHomeUp();
}

@Override
public void onBackStackChanged() {
    shouldDisplayHomeUp();
}

public void shouldDisplayHomeUp(){
   //Enable Up button only  if there are entries in the back stack
   boolean canGoBack = getSupportFragmentManager().getBackStackEntryCount()>0;
   getSupportActionBar().setDisplayHomeAsUpEnabled(canGoBack);
}

@Override
public boolean onSupportNavigateUp() {
    //This method is called when the up button is pressed. Just the pop back stack.
    getSupportFragmentManager().popBackStack();
    return true;
}

Upvotes: 188

fada21

Reputation: 3278

Kotlin:

class MyActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        ...
        supportFragmentManager.addOnBackStackChangedListener { setupHomeAsUp() }
        setupHomeAsUp()
    }

    private fun setupHomeAsUp() {
        val shouldShow = 0 < supportFragmentManager.backStackEntryCount
        supportActionBar?.setDisplayHomeAsUpEnabled(shouldShow)
    }

    override fun onSupportNavigateUp(): Boolean = 
        supportFragmentManager.popBackStack().run { true }

    ...
}

Upvotes: 5

bebe

Reputation: 114

This worked for me. Override onSupportNavigateUp and onBackPressed, for example (code in Kotlin);

override fun onBackPressed() {
    val count = supportFragmentManager.backStackEntryCount
    if (count == 0) {
        super.onBackPressed()
    } else {
        supportFragmentManager.popBackStack()
    }
}

override fun onSupportNavigateUp(): Boolean {
    super.onSupportNavigateUp()
    onBackPressed()
    return true
}

Now in the fragment, if you display the up arrow

activity.supportActionBar?.setDisplayHomeAsUpEnabled(true)

Clicking on it takes you back the previous activity.

Upvotes: 5

martom

Reputation: 763

I know this question is old, but may be someone (like me) also needs it.

If your Activity extends AppCompatActivity, you can use a simpler (two-step) solution:

1 - Whenever you add a non-home fragment just show the up button, right after commiting the fragment transaction. Like this:

    // ... add a fragment
    // Commit the transaction
    transaction.commit();

    getSupportActionBar().setDisplayHomeAsUpEnabled(true);

2 - Then when UP button is pressed, you hide it.

@Override
public boolean onSupportNavigateUp() {
    getSupportActionBar().setDisplayHomeAsUpEnabled(false);        
    return true;
}

That's it.

Upvotes: 9

verboze

Reputation: 419

I used a combination of Roger Garzon Nieto's and sohailaziz's answers. My app has a single MainActivity, and fragments A, B, C that are loaded into it. My "home" fragment (A) implements OnBackStackChangedListener, and checks the size of the backStack; if it's less than one, then it hides the UP button. Fragments B and C always load the back button (in my design, B is launched from A, and C is launched from B). The MainActivity itself just pops the backstack on UP button tap, and has methods to show/hide the button, which the fragments call:

MainActivity:

public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
        // Respond to the action bar's Up/Home button
        case android.R.id.home:
            getSupportFragmentManager().popBackStack();
            return true;
    }
    return super.onOptionsItemSelected(item);
}

public void showUpButton() { getSupportActionBar().setDisplayHomeAsUpEnabled(true); }
public void hideUpButton() { getSupportActionBar().setDisplayHomeAsUpEnabled(false); }

fragmentA (implements FragmentManager.OnBackStackChangedListener):

public void onCreate(Bundle savedinstanceSate) {
    // listen to backstack changes
    getActivity().getSupportFragmentManager().addOnBackStackChangedListener(this);

    // other fragment init stuff
    ...
}

public void onBackStackChanged() {
    // enable Up button only  if there are entries on the backstack
    if(getActivity().getSupportFragmentManager().getBackStackEntryCount() < 1) {
        ((MainActivity)getActivity()).hideUpButton();
    }
}

fragmentB, fragmentC:

public void onCreate(Bundle savedinstanceSate) {
    // show the UP button
    ((MainActivity)getActivity()).showUpButton();

    // other fragment init stuff
    ...
}

Upvotes: 8

Moaz Rashad

Reputation: 1075

you can go back with up button like back button ;

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
        case android.R.id.home:
            super.onBackPressed();
            return true;
    }
    return super.onOptionsItemSelected(item);
}

Upvotes: 11

Amio.io

Reputation: 21575

This is a very good and reliable solution: http://vinsol.com/blog/2014/10/01/handling-back-button-press-inside-fragments/

The guy has made an abstract fragment that handles the backPress behaviour and is switching between the active fragments using the strategy pattern.

For some of you there maybe a little drawback in the abstract class...

Shortly, the solution from the link goes like this:

// Abstract Fragment handling the back presses

public abstract class BackHandledFragment extends Fragment {
    protected BackHandlerInterface backHandlerInterface;
    public abstract String getTagText();
    public abstract boolean onBackPressed();

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if(!(getActivity()  instanceof BackHandlerInterface)) {
            throw new ClassCastException("Hosting activity must implement BackHandlerInterface");
        } else {
            backHandlerInterface = (BackHandlerInterface) getActivity();
        }
    }

    @Override
    public void onStart() {
        super.onStart();

        // Mark this fragment as the selected Fragment.
        backHandlerInterface.setSelectedFragment(this);
    }

    public interface BackHandlerInterface {
        public void setSelectedFragment(BackHandledFragment backHandledFragment);
    }
}

And usage in the activity:

// BASIC ACTIVITY CODE THAT LETS ITS FRAGMENT UTILIZE onBackPress EVENTS 
// IN AN ADAPTIVE AND ORGANIZED PATTERN USING BackHandledFragment

public class TheActivity extends FragmentActivity implements BackHandlerInterface {
    private BackHandledFragment selectedFragment;

    @Override
    public void onBackPressed() {
        if(selectedFragment == null || !selectedFragment.onBackPressed()) {
            // Selected fragment did not consume the back press event.
            super.onBackPressed();
        }
    }

    @Override
    public void setSelectedFragment(BackHandledFragment selectedFragment) {
        this.selectedFragment = selectedFragment;
    }
}

Upvotes: 2

Daniel Jonker

Reputation: 854

If you have one parent activity and want this up button to work as a back button, you can use this code:

add this to the onCreate in your main activity class

getSupportFragmentManager().addOnBackStackChangedListener(new FragmentManager.OnBackStackChangedListener() {
        @Override
        public void onBackStackChanged() {
            int stackHeight = getSupportFragmentManager().getBackStackEntryCount();
            if (stackHeight > 0) { // if we have something on the stack (doesn't include the current shown fragment)
                getSupportActionBar().setHomeButtonEnabled(true);
                getSupportActionBar().setDisplayHomeAsUpEnabled(true);
            } else {
                getSupportActionBar().setDisplayHomeAsUpEnabled(false);
                getSupportActionBar().setHomeButtonEnabled(false);
            }
        }

    });

and then add onOptionsItemSelected like so:

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
        case android.R.id.home:
            getSupportFragmentManager().popBackStack();
            return true;
     ....
 }

I generally use this all the time and seems pretty legit

Upvotes: 18

actionbar up navigation with fragments

Answers (10)

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