Question

我是Android开发的新手，正在关注＆＃34; Adding Action Bar Tutorial＆＃34;

我试图获取操作栏上的主页（后面的胡萝卜）按钮，以使我的应用程序返回主要活动。

在教程中提到，如果在xml中定义了父项，则可以在不处理向上按钮事件的情况下完成此操作。

下面是我的xml文件

<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>

但按下胡萝卜按钮不起作用。我能做错什么？

编辑：添加以下活动代码

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低于

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;
        }
    }

}

由于

Answer 1

@Newton如果您正在使用parentActivityName属性，那么调用ActionBar.setDisplayHomeAsUpEnabled（true）实际上是多余的。也就是说，当您从DisplayMessageActivity中删除该行时，是＆＃ 34;向上＆＃34;可供性仍然存在？ - 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);

操作栏上的主页按钮

3 个答案: