Android - Switch ActionBar Back Button to Navigation Button

If I assume you're using android.support.v4.widget.DrawerLayout in your layout, then this approach may work for you; I've only tested on API 21 but given it's mostly using the support libraries, it should work (famous last words) on lower or higher targets.

import android.support.v7.app.ActionBarDrawerToggleimport android.support.v4.widget.DrawerLayout    ActionBarDrawerToggle mDrawerToggle;    DrawerLayout drawerLayout;    private boolean mToolBarNavigationListenerIsRegistered = false;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setSupportActionBar(mToolbar);        getSupportActionBar().setDisplayShowTitleEnabled(false);        // Get DrawerLayout ref from layout        drawerLayout = (DrawerLayout)findViewById(R.id.drawer);        // Initialize ActionBarDrawerToggle, which will control toggle of hamburger.        // You set the values of R.string.open and R.string.close accordingly.        // Also, you can implement drawer toggle listener if you want.        mDrawerToggle = new ActionBarDrawerToggle (this, drawerLayout, mToolbar, R.string.open, R.string.close);        // Setting the actionbarToggle to drawer layout        drawerLayout.addDrawerListener(mDrawerToggle);        // Calling sync state is necessary to show your hamburger icon...        // or so I hear. Doesn't hurt including it even if you find it works        // without it on your test device(s)        mDrawerToggle.syncState();    }    /**     * To be semantically or contextually correct, maybe change the name     * and signature of this function to something like:     *     * private void showBackButton(boolean show)     * Just a suggestion.     */     private void enableViews(boolean enable) {        // To keep states of ActionBar and ActionBarDrawerToggle synchronized,        // when you enable on one, you disable on the other.        // And as you may notice, the order for this operation is disable first, then enable - VERY VERY IMPORTANT.        if(enable) {            //You may not want to open the drawer on swipe from the left in this case              drawerLayout.setDrawerLockMode(DrawerLayout.LOCK_MODE_LOCKED_CLOSED);            // Remove hamburger            mDrawerToggle.setDrawerIndicatorEnabled(false);            // Show back button            getSupportActionBar().setDisplayHomeAsUpEnabled(true);            // when DrawerToggle is disabled i.e. setDrawerIndicatorEnabled(false), navigation icon            // clicks are disabled i.e. the UP button will not work.            // We need to add a listener, as in below, so DrawerToggle will forward            // click events to this listener.            if(!mToolBarNavigationListenerIsRegistered) {                mDrawerToggle.setToolbarNavigationClickListener(new View.OnClickListener() {                    @Override                    public void onClick(View v) {                        // Doesn't have to be onBackPressed                        onBackPressed();                    }                });                mToolBarNavigationListenerIsRegistered = true;            }        } else {            //You must regain the power of swipe for the drawer.             drawerLayout.setDrawerLockMode(DrawerLayout.LOCK_MODE_UNLOCKED);            // Remove back button            getSupportActionBar().setDisplayHomeAsUpEnabled(false);            // Show hamburger             mDrawerToggle.setDrawerIndicatorEnabled(true);            // Remove the/any drawer toggle listener            mDrawerToggle.setToolbarNavigationClickListener(null);            mToolBarNavigationListenerIsRegistered = false;        }        // So, one may think "Hmm why not simplify to:        // .....        // getSupportActionBar().setDisplayHomeAsUpEnabled(enable);        // mDrawer.setDrawerIndicatorEnabled(!enable);        // ......        // To re-iterate, the order in which you enable and disable views IS important #dontSimplify.    }

The solution uses ActionBarDrawerToggle.setDrawerIndicatorEnabled to toggle the visibility of the hamburger icon and ActionBar.setDisplayHomeAsUpEnabled for visibility of the Up button, essentially making use of their respective drawable resources.

Other assumptions

• Your Activity theme extends Theme.AppCompat.Light.NoActionBar.

The top solutions did not work in this case:

• One Activity and multiple Fragments
• One Fragment (SettingsFragment) should show the back icon instead of the burger menu
• Using com.google.android.material.appbar.AppBarLayout, androidx.appcompat.widget.Toolbar and ActionBarDrawerToggle

I call this method in my Activity's onCreate():

private fun initBackStackChangeListener() {    supportFragmentManager.addOnBackStackChangedListener {        val fragment = supportFragmentManager.findFragmentById(R.id.fragment_container)        if (fragment is SettingsFragment) {            menuDrawerToggle?.isDrawerIndicatorEnabled = false            drawer_layout.setDrawerLockMode(DrawerLayout.LOCK_MODE_LOCKED_CLOSED)            menuDrawerToggle?.setToolbarNavigationClickListener { onBackPressed() }            supportActionBar?.setDisplayHomeAsUpEnabled(true)        } else {            supportActionBar?.setDisplayHomeAsUpEnabled(false)            drawer_layout.setDrawerLockMode(DrawerLayout.LOCK_MODE_UNLOCKED)            menuDrawerToggle?.isDrawerIndicatorEnabled = true            menuDrawerToggle?.toolbarNavigationClickListener = null            menuDrawerToggle?.syncState()        }    }}

And menuDrawerToggle is this:

menuDrawerToggle = ActionBarDrawerToggle(        this, drawer_layout, toolbar,        R.string.navigation_drawer_open,        R.string.navigation_drawer_close    ).apply {        drawer_layout.addDrawerListener(this)        this.syncState()    }

Works like a charm. Maybe it helps anybody.

I found flexible solutions in The Google I/O 2017 Android App.

public Toolbar getToolbar() {    if (mToolbar == null) {        mToolbar = (Toolbar) findViewById(R.id.toolbar);        if (mToolbar != null) {            setSupportActionBar(mToolbar);            mToolbar.setNavigationContentDescription(R.string.navdrawer_description_a11y);            mToolbarTitle = (TextView) mToolbar.findViewById(R.id.toolbar_title);            if (mToolbarTitle != null) {                int titleId = getNavigationTitleId();                if (titleId != 0) {                    mToolbarTitle.setText(titleId);                }            }            // We use our own toolbar title, so hide the default one            getSupportActionBar().setDisplayShowTitleEnabled(false);        }    }    return mToolbar;}/** * @param clickListener The {@link android.view.View.OnClickListener} for the navigation icon of *                      the toolbar. */protected void setToolbarAsUp(View.OnClickListener clickListener) {    // Initialise the toolbar    getToolbar();    if (mToolbar != null) {        mToolbar.setNavigationIcon(R.drawable.ic_up);        mToolbar.setNavigationContentDescription(R.string.close_and_go_back);        mToolbar.setNavigationOnClickListener(clickListener);    }}

So the usage is really simple.

setToolbarAsUp(new View.OnClickListener() {    @Override    public void onClick(View v) {        // onBackPressed();        // or navigate to parent or some other intent    }});