ActionBarDrawerToggle with AppCompatActivity and Toolbar Back button with Fragments

Question

I am using the ActionBarDrawerToggle with NavigationView. My content is displayed using fragments.

I am following this stackoverflow question to get the back button press to work but control never flows to onOptionsItemSelected.

This is my MainActivity.class:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
    mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout, toolbar, R.string.openDrawerContentDescRes, R.string.closeDrawerContentDescRes);
    mDrawerLayout.addDrawerListener(mDrawerToggle);
    mDrawerToggle.syncState();

@Override
public void onBackPressed() {
    if (getFragmentManager().getBackStackEntryCount() == 0) {
        super.onBackPressed();
    } else {
        removeFragmentFromBackstack();
        updateToolbarWithHomeButton();
    }

}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    if (mDrawerToggle.onOptionsItemSelected(item)) {
        return true;
    }

    switch (item.getItemId()) {
        case android.R.id.home:
            // doesn't reach here ever.
            return true;
        case R.id.action_x:
            // do something
            return true;
        case R.id.action_y:
            // do something
            return true;
        default:
            return super.onOptionsItemSelected(item);
    }
}

@Override
protected void onPostCreate(Bundle savedInstanceState) {
    super.onPostCreate(savedInstanceState);
    // Sync the toggle state after onRestoreInstanceState has occurred.
    mDrawerToggle.syncState();
}

@Override
public void onConfigurationChanged(Configuration newConfig) {
    super.onConfigurationChanged(newConfig);
    mDrawerToggle.onConfigurationChanged(newConfig);
}

private void updateToolbarWithBackButton() {
    ActionBar actionBar = getSupportActionBar();
    if (null != mDrawerToggle && null != actionBar) {
        mDrawerToggle.setDrawerIndicatorEnabled(false);
        actionBar.setDisplayHomeAsUpEnabled(true);
    }
}

private void updateToolbarWithHomeButton() {
    ActionBar actionBar = getSupportActionBar();
    if (null != mDrawerToggle && null != actionBar) {
        actionBar.setDisplayHomeAsUpEnabled(false);
        mDrawerToggle.setDrawerIndicatorEnabled(true);
        mDrawerToggle.syncState();
    }
}

How can I capture the Back button <- click from Toolbar?

---

Update:

Thanks to @mike the back arrow button on the toolbar is now captured within the onOptionsItemSelected in my MainActivity code as updated below.

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    getSupportActionBar().setDisplayHomeAsUpEnabled(true);

    mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
    mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout, R.string.openDrawerContentDescRes, R.string.closeDrawerContentDescRes);
    mDrawerLayout.addDrawerListener(mDrawerToggle);
    mDrawerToggle.syncState();

@Override
public void onBackPressed() {
    if (getFragmentManager().getBackStackEntryCount() == 0) {
        super.onBackPressed();
    } else {
        removeFragmentFromBackstack();
        updateToolbarWithHomeButton();
    }

}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
        case android.R.id.home:
            //TODO: skip back press if fragment backstack count is 0.
            onBackPressed();
            updateToolbarWithHomeButton();
            return true;
        case R.id.action_x:
            // do something
            return true;
        case R.id.action_y:
            // do something
            return true;
        default:
            return super.onOptionsItemSelected(item);
    }
}

@Override
protected void onPostCreate(Bundle savedInstanceState) {
    super.onPostCreate(savedInstanceState);
    // Sync the toggle state after onRestoreInstanceState has occurred.
    mDrawerToggle.syncState();
}

@Override
public void onConfigurationChanged(Configuration newConfig) {
    super.onConfigurationChanged(newConfig);
    mDrawerToggle.onConfigurationChanged(newConfig);
}

private void updateToolbarWithBackButton() {
    ActionBar actionBar = getSupportActionBar();
    if (null != mDrawerToggle && null != actionBar) {
        mDrawerToggle.setDrawerIndicatorEnabled(false);
    }
}

private void updateToolbarWithHomeButton() {
    ActionBar actionBar = getSupportActionBar();
    if (null != mDrawerToggle && null != actionBar) {
        mDrawerToggle.setDrawerIndicatorEnabled(true);
        mDrawerToggle.syncState();
    }
}

Answer 1

If you want the onOptionsItemSelected() method to fire upon clicking the toggle, remove the toolbar argument from the ActionBarDrawerToggle constructor call.

mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout,
    R.string.openDrawerContentDescRes, R.string.closeDrawerContentDescRes);

Otherwise, the toggle handles opening and closing the drawer internally, and the call to ActionBarDrawerToggle#onOptionsItemSelected() isn't necessary.

If you want to handle clicking the home Button differently depending on the current state, you'll also want to remove the if block that returns at the top of the onOptionsItemSelected() method.

And, you should call setDisplayHomeAsUpEnabled(true) just once in onCreate(). You don't need to keep switching that on and off. Enabling and disabling the drawer indicator will take care of that.