How to implement the Android ActionBar back button?

Back button implementation details

Here's a step-by-step guide to getting that ActionBar back button up and running smoothly.

Declare relationships in the AndroidManifest.xml

Your AndroidManifest.xml needs to know who's who in the hierarchy:

<activity
    android:name=".ChildActivity"
    android:label="@string/title_child"
    android:parentActivityName=".ParentActivity" >
    <!-- Sure you're under 16? Proof, please! -->
    <meta-data
        android:name="android.support.PARENT_ACTIVITY"
        android:value=".ParentActivity" />
</activity>
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Overriding onOptionsItemSelected

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
        // Clicking home? Surprise, surprise!
        case android.R.id.home:
            NavUtils.navigateUpFromSameTask(this);
            return true;
    }
    return super.onOptionsItemSelected(item);
}
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Up navigation for ancient APIs

For API level 16 and lower, honor the elderly and use NavUtils.navigateUpFromSameTask(this). Just make sure the meta-data in the manifest is set.

Base activity for consistency

Consistency is key. Create a base activity that calls setDisplayHomeAsUpEnabled(true) and make all child activities extend it. Now sit back and watch the magic flow.

Respect the activity lifecycle

The lifecycle of activities. Sounds profound, right? Brush up on onPause, onResume, etc., before delving into onOptionsItemSelected.

Verify theme and initialize ActionBar

Check that your app's theme isn't too fancy for an ActionBar and initialize the ActionBar in your onCreate:

Toolbar toolbar = findViewById(R.id.toolbar); // The chosen one
setSupportActionBar(toolbar); // The one to rule them all
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Keep it consistent

Remember the 'Rule of Thumb' - apply back button functionality uniformly across activities. No exceptions!

Know when to use onBackPressed vs finish

'Finish' is the Kanye West, immediately closing the activity. The humble 'onBackPressed' sticks to the standard back stack behavior.

Essential tips for flaw-free ActionBar back button

A well-executed ActionBar back button can greatly enhance your app's user experience.

Check manifest configurations

Double-check the parent-children declarations in your manifest. Nobody likes a homeless activity!

Working with onBackPressed method

Consider some cleanup operations or data saving magic in your onBackPressed:

@Override
public void onBackPressed() {
    // Conduct your symphony of cleanup here
    super.onBackPressed(); // Don't be rude! Call your super!
}
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Implement onSupportNavigateUp

When using ActionBarDrawerToggle, you must override onSupportNavigateUp to handle navigation drawer clicks and assist navigation:

@Override
public boolean onSupportNavigateUp() {
    onBackPressed(); // Because repeating ourselves is fun!
    return true;
}
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