Android - Back button in the title bar

use this code

 @Override
 public void onCreate(Bundle savedInstanceState) {
    ...
   getActionBar().setDisplayHomeAsUpEnabled(true);
 } 

after that write this code in onOptionsItemSelected method

  int id = item.getItemId();

     if (id==android.R.id.home) {
        finish();
    }

1.- Add the activity to AndroidManifest.xml and make sure to provide the meta-data:

<activity
    android:name="com.example.myfirstapp.DisplayMessageActivity"
    android:label="@string/title_activity_display_message"
    android:parentActivityName="com.example.myfirstapp.MainActivity" >
    <!-- Parent activity meta-data to support 4.0 and lower -->
    <meta-data
        android:name="android.support.PARENT_ACTIVITY"
        android:value="com.example.myfirstapp.MainActivity" />
</activity>

2.- Add the following code to the onCreate method of the activity:

@Override
public void onCreate(Bundle savedInstanceState) {
    ...
    getActionBar().setDisplayHomeAsUpEnabled(true);
} 

3.- Override the onOptionsItemSelected and use NavUtils.navigateUpFromSameTask() static method to navigate throw the stack.

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

However, using navigateUpFromSameTask() is suitable only when your app is the owner of the current task (that is, the user began this task from your app). If that's not true and your activity was started in a task that belongs to a different app, then navigating Up should create a new task that belongs to your app, which requires that you create a new back stack.

There are two simple steps to create a back button in the title bar:

First, make the application icon clickable using the following code in the activity whose title bar you want to have a back button in:

ActionBar actionBar = getActionBar();
actionBar.setDisplayHomeAsUpEnabled(true);

After you have added the above code, you will see a back arrow appear to the left of the application icon.

Second, after you have done the above, you still have to create code that will take advantage of the click event. To do so, be aware that, when you actually click on the application icon, an onOptionsItemSelected method is called. So to go back to the previous activity, add that method to your activity and put Intent code in it that will return you to the previous activity. For example, let's say the activity you are trying to go back to is called MyActivity. To go back to it, write the method as follows:

public boolean onOptionsItemSelected(MenuItem item){
    Intent myIntent = new Intent(getApplicationContext(), MyActivity.class);
    startActivityForResult(myIntent, 0);
    return true;
}

That's it!

(In the Android developers API, it recommends messing around with the manifest and adding stuff like android:parentActivityName. But that doesn't seem to work for me. The above is simpler and more reliable.)

<meta-data
      android:name="android.support.PARENT_ACTIVITY"
      android:value=".MainActivity" />

And in your Activity

getSupportActionBar().setDisplayHomeAsUpEnabled(true);

I have finally managed to properly add back button to actionbar/toolbar

@Override
public void onCreate(Bundle savedInstanceState) {
    ...
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);
}  

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

    return super.onOptionsItemSelected(item);
}

public boolean onCreateOptionsMenu(Menu menu) {
    return true;
}