Toolbar - Switching from drawer to back button with only one Activity

Question

I've been searching for a while on how to change between the drawer open/close icon (going from a hamburger to the arrow) to a simple back arrow. My application at the moment only has one Activity which switches between several fragments. At one point, I want to transition between one of the main fragments (ie, one of the fragments in the drawer) to a fragment that hierarchically is under the previous fragment (ie, an "Add New " fragment). In this new fragment, I want to have the Toolbar to show the back button instead of the drawer button.

I've been looking around and trying different solutions for quite a while. Here are the most notable:

• Change drawer icon back to back arrow - I successfully removed the drawer icon, but in place there's.... nothing. No up caret, no back button, no icon. I suspect this is because my Activity has no parent, but other than a cheap work around (create another Activity that acts as a parent which launches the main Activity), I'm at a lost of what to do.
• Switching between Android Navigation Drawer image and Up caret when using fragments - Similar to the above, yet has far more detail. Ultimately, the icon still doesn't turn into a back button.
• Android lollipop toolbar switch between open/close drawer and back button - I find this hard to follow, but ultimately the drawer icon can be tapped and does nothing (although I believe I know how to make it act as a back press). However, the icon doesn't change.

At the moment, I'm thinking of a long, arduous method of creating a custom icon that I hide and show (and hide/show the native drawer icon). However, is there a better way to switch between the drawer and back buttons?

As a side yet related question, I've been looking at the Material Design docs, and a few examples have an X in the top left corner. How different is that to implement than implementing the drawer vs back/up buttons?

Thanks~

Edit:

I can figure out how to replace the icon, but how would I get the click event?

So far, this was my best lead:

• Cannot catch toolbar home button click event

What I've tried now:

• Disabled the DrawerToggle when necessary (ie, mDrawerToggle.setDrawerIndicatorEnabled(useDrawer);)
• Added logs in onOptionsItemSelected in my NavigationDrawerFragment, my Activity, as well as the DialogFragment I'm currently testing which run if item.getItemId() == android.R.id.home is true. None of these log statements go off

For better context, I now have a full screen fragment which adds a "Save" button to the menu and changes the drawer icon to an "X". The fragment can get the save menu event, yet not even the Activity and Drawer can get when the X is tapped.

Edit2:

As requested, here is some code. Note that this is all from this Github repo, which I'm actively working on (note that I have a few useless functions here or there from rapid testing).

ActivityMain:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    // Add the toolbar
    mToolbar = (Toolbar) findViewById(R.id.toolbar);
    if (mToolbar != null) {
        setSupportActionBar(mToolbar);
    }

    // Initialize the drawer
    mNavigationDrawerFragment = (NavigationDrawerFragment)
            getSupportFragmentManager().findFragmentById(R.id.navigation_drawer);

    // Set up the drawer
    mNavigationDrawerFragment.setUp(
            R.id.navigation_drawer,
            (DrawerLayout) findViewById(R.id.drawer_layout),
            mToolbar);

    // TODO: Check if this helps to catch the main toolbar button click
    getSupportActionBar().setDisplayShowHomeEnabled(true);

    // Get the titles for the Toolbar
    mTitles = getResources().getStringArray(R.array.drawer_items);

    mDrawerPosition = -1;
    if (savedInstanceState == null) {
        // If there was no saved position, then the default, starting position should be used
        forceChangeItemSelected(0);
    }
    else {
        // Otherwise, get the saved position from the bundle
        int position = savedInstanceState.getInt(KEY_DRAWERPOS);
        mNavigationDrawerFragment.setSelectedItem(position);
        // Title needs to be re-set
        getSupportActionBar().setTitle(mTitles[position]);
    }

    // If I include the below bit, then the DrawerToggle doesn't function
        // I don't know how to switch it back and forth
    mToolbar.setNavigationOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Log.d(LOG_TAG, "Navigation was clicked");

        }
    });
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    Log.d(LOG_TAG, "Activity responding to menu click...");
    if(item.getItemId() == android.R.id.home) Log.d(LOG_TAG, "Activity got it....");

    // If the fragment is supposed to handle things, then let it
    if(mIsFragmentHandlingMenus) return false;

    int id = item.getItemId();
    if(id == R.id.save) {
        // This isn't implemented! If chosen, then there's a bug!
        Log.e(LOG_TAG, "onOptionsItemSelected: Save was selected!");
    }

    return super.onOptionsItemSelected(item);
}

@Override
public void fragmentHandlingMenus(boolean isFragmentHandlingMenus) {
    // Simply store the setting
    mIsFragmentHandlingMenus = isFragmentHandlingMenus;

    // Toggle the drawer as necessary
    mNavigationDrawerFragment.toggleDrawerUse(!isFragmentHandlingMenus);
}

NavigationDrawerFragment:

public void toggleDrawerUse(boolean useDrawer) {
    // Enable/Disable the icon being used by the drawer
    mDrawerToggle.setDrawerIndicatorEnabled(useDrawer);

    // TODO: Enable/Disable the drawer even being able to open/close
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    Log.d(LOGTAG, "Drawer responding to menu click...");
    if(item.getItemId() == android.R.id.home) Log.d(LOGTAG, "Drawer got it....");
    if (mDrawerToggle.onOptionsItemSelected(item)) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}

GoalAdderFragment:

@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    // Allow this fragment to handle toolbar menu items
    setHasOptionsMenu(true);

    // Set up the toolbar
    ((ActionBarActivity) getActivity()).getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    ((ActionBarActivity) getActivity()).getSupportActionBar().setHomeAsUpIndicator(android.R.drawable.ic_menu_close_clear_cancel);
    ((ActionBarActivity) getActivity()).getSupportActionBar().setTitle(getResources().getString(R.string.title_addgoal));
}

@Override
public void onAttach(Activity activity) {
    super.onAttach(activity);

    // Cache the Activity as the frag handler if necessary
    if(mFragHandler == null)
        mFragHandler = (TransactionHandler.FragmentTransactionHandler) getActivity();
    // Tell the Activity to let fragments handle the menu events
    mFragHandler.fragmentHandlingMenus(true);
}

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

    // Tell the Activity that it can now handle menu events once again
    mFragHandler.fragmentHandlingMenus(false);
}

@Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
    inflater.inflate(R.menu.save_menu, menu);
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    Log.d(LOGTAG, "Item id: " + item.getItemId() + " | Save id: " + R.id.save);
    Toast.makeText(getActivity(), "Fragment activated!", Toast.LENGTH_SHORT).show();

    switch (item.getItemId()) {
        case R.id.save:
            return true;
        case android.R.id.home:
            return true;
        default:
            break;
    }

    return false;
}

Solution:

This is the ultimate solution I ended up on, with the help of natario's answer below:

NavigationDrawerFragment:

private View.OnClickListener mOriginalListener;

public void setUp(int fragmentId, DrawerLayout drawerLayout, Toolbar toolbar) {
     /* Rest of setting up code */

     // Save the default listener after setting everything else up
     mOriginalListener = mDrawerToggle.getToolbarNavigationClickListener();
}

// Tells the toolbar+drawer to switch to the up button or switch back to the normal drawer
public void toggleDrawerUse(boolean useDrawer) {
    // Enable/Disable the icon being used by the drawer
    mDrawerToggle.setDrawerIndicatorEnabled(useDrawer);

    // Switch between the listeners as necessary
    if(useDrawer)
        mDrawerToggle.setToolbarNavigationClickListener(mOriginalListener);
    else
        mDrawerToggle.setToolbarNavigationClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(getActivity(), "Custom listener", Toast.LENGTH_SHORT).show();
            }
        });
}

Answer 1

Put this code into onCreate() of your Activity. Works well for me. Even using compileSdk 23 and higher.

    drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    final Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    if(toolbar != null) {
        toggle = new ActionBarDrawerToggle(
                this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
        toggle.syncState();
        drawer.setDrawerListener(toggle);
        getSupportFragmentManager().addOnBackStackChangedListener(new FragmentManager.OnBackStackChangedListener() {
            @Override
            public void onBackStackChanged() {
                if (getSupportFragmentManager().getBackStackEntryCount() > 0) {
                    getSupportActionBar().setDisplayHomeAsUpEnabled(true); // show back button
                    toolbar.setNavigationOnClickListener(new View.OnClickListener() {
                        @Override
                        public void onClick(View v) {
                            onBackPressed();
                        }
                    });
                } else {
                    //show hamburger
                    getSupportActionBar().setDisplayHomeAsUpEnabled(false);
                    toggle.syncState();
                    toolbar.setNavigationOnClickListener(new View.OnClickListener() {
                        @Override
                        public void onClick(View v) {
                            drawer.openDrawer(GravityCompat.START);
                        }
                    });
                }
            }
        });