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Question

I am new to android development and was following the " Adding Action Bar Tutorial "

I was trying to get the home (back carrot) button on the action bar to enable my app to go back to the main activity.

It is mentioned in the tutorial that this can be done without handling the up button event, if the parent is defined in the xml.

below is my xml file

<activity
    android:name="com.example.firstapp.DisplayMessageActivity"
    android:label="@string/title_activity_display_message"
    android:parentActivityName="com.example.myfirstapp.MainActivity" >
    <meta-data
        android:name="android.support.PARENT_ACTIVITY"
        android:value="com.example.myfirstapp.MainActivity" />
</activity>

but pressing the carrot button does not work. what can i be doing wrong?

EDIT: adding the activity code below

public class DisplayMessageActivity extends ActionBarActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        /*
         * setContentView(R.layout.activity_display_message); if
         * (savedInstanceState == null) {
         * getSupportFragmentManager().beginTransaction() .add(R.id.container,
         * new PlaceholderFragment()).commit(); }
         */

        // Get the message from the intent
        Intent intent = getIntent();
        String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);

        // Create the text view
        TextView textView = new TextView(this);
        textView.setTextSize(40);
        textView.setText(message);

        // Set the text view as the activity layout
        setContentView(textView);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    }

    @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.
        /*
         * switch (item.getItemId()) { case android.R.id.home: Intent intent =
         * new Intent(getApplicationContext(),
         * com.example.firstapp.MainActivity.class);
         * intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
         * startActivity(intent); return true; default: return
         * super.onOptionsItemSelected(item); }
         */
        return super.onOptionsItemSelected(item);
    }

    /**
     * A placeholder fragment containing a simple view.
     */
    public static class PlaceholderFragment extends Fragment {

        public PlaceholderFragment() {
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_display_message,
                    container, false);
            return rootView;
        }
    }

}

MainActivity is below

public class MainActivity extends ActionBarActivity {

    public final static String EXTRA_MESSAGE = "com.example.myfirstapp.MESSAGE";

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

        if (savedInstanceState == null) {
            getSupportFragmentManager().beginTransaction()
                    .add(R.id.container, new PlaceholderFragment())
                    .commit();
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu items for use in the action bar
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.main, menu);
        return super.onCreateOptionsMenu(menu);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle presses on the action bar items
        switch (item.getItemId()) {
            case R.id.action_search:
                // openSearch();
                EditText temp1 = (EditText) findViewById(R.id.edit_message);
                temp1.setText("Search");
                return true;
            case R.id.action_settings:
                // openSettings();
                EditText temp2 = (EditText) findViewById(R.id.edit_message);
                temp2.setText("Settings");
                return true;
            case android.R.id.home:
                NavUtils.navigateUpFromSameTask(this);
                return true;
            default:
                return super.onOptionsItemSelected(item);
        }
    }

    /** Called when the user clicks the Send button */
    public void sendMessage(View view) {
        // Do something in response to button
        Intent intent = new Intent(this, DisplayMessageActivity.class);
        EditText editText = (EditText) findViewById(R.id.edit_message);
        String message = editText.getText().toString();
        intent.putExtra(EXTRA_MESSAGE, message);
        startActivity(intent);
    }

    /**
     * A placeholder fragment containing a simple view.
     */
    public static class PlaceholderFragment extends Fragment {

        public PlaceholderFragment() {
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_main, container, false);
            return rootView;
        }
    }

}

Thanks

Answer 1

@Newton It's actually redundant to call ActionBar.setDisplayHomeAsUpEnabled(true), if you're using the parentActivityName attribute.. That being said, when you remove that line from your DisplayMessageActivity, is the "up" affordance still present? – adneal

Answer 2

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
        case android.R.id.home:
            // app icon in action bar clicked; go home
            Intent intent = new Intent(this, HomeActivity.class);
            intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
            startActivity(intent);
            return true;
        default:
            return super.onOptionsItemSelected(item);
    }
}

Answer 3

在您的活动中使用

    getActionBar().setDisplayHomeAsUpEnabled(true);