Question

我有一个扩展活动的DrawbleActivity类，getActionBar（）给我nullpointerexception（）。

当我更改ActionBarActivity的扩展时，它可以工作！但是没有显示ic_drawer我正在尝试构建一个导航抽屉。

我会遇到主题或活动的问题吗？ minsdkversion是14我使用IDE eclipse luna。

public class DrawbleActivity extends Activity {
    private DrawerLayout mDrawerLayout;
    private ListView mDrawerList;
    private ActionBarDrawerToggle mDrawerToggle;

    private CharSequence mDrawerTitle;
    private CharSequence mTitle;
    private String[] mPlanetTitles;

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

        mTitle = mDrawerTitle = getTitle();
        mPlanetTitles = getResources().getStringArray(R.array.Filtro);
        mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
        mDrawerList = (ListView) findViewById(R.id.left_drawer);

        // set a custom shadow that overlays the main content when the drawer opens
        mDrawerLayout.setDrawerShadow(R.drawable.drawer_shadow, GravityCompat.START);
        // set up the drawer's list view with items and click listener
        mDrawerList.setAdapter(new ArrayAdapter<String>(this,
                R.layout.drawer_list_item, mPlanetTitles));
        mDrawerList.setOnItemClickListener(new DrawerItemClickListener());

        // enable ActionBar app icon to behave as action to toggle nav drawer

        getActionBar().setDisplayHomeAsUpEnabled(true);
        getActionBar().setHomeButtonEnabled(true);

        // ActionBarDrawerToggle ties together the the proper interactions
        // between the sliding drawer and the action bar app icon
        mDrawerToggle = new ActionBarDrawerToggle(
                this,                  /* host Activity */
                mDrawerLayout,         /* DrawerLayout object */
                R.drawable.ic_drawer,  /* nav drawer image to replace 'Up' caret */
                R.string.drawer_open,  /* "open drawer" description for accessibility */
                R.string.drawer_close  /* "close drawer" description for accessibility */
                ) {
            public void onDrawerClosed(View view) {
                getActionBar().setTitle(mTitle);
                invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
            }

            public void onDrawerOpened(View drawerView) {
                getActionBar().setTitle(mDrawerTitle);
                invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
            }
        };
        mDrawerLayout.setDrawerListener(mDrawerToggle);

        if (savedInstanceState == null) {
            selectItem(0);
        }
    }

Answer 1

关于＆＃39; openOptionsMenu（）＆＃39; ..看到这个链接：http://blog.perpetumdesign.com/2011/08/strange-case-of-dr-action-and-mr-bar.html;如果你的清单中有这一行android:theme="@style/Theme.NoTitle" jsut将其删除并重试。

Answer 2

您必须通过以下代码请求操作栏。

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    // request for action bar-----------------------------
    getWindow().requestFeature(Window.FEATURE_ACTION_BAR);

    setContentView(R.layout.main);

    getActionBar().setDisplayHomeAsUpEnabled(true);
    getActionBar().setHomeButtonEnabled(true);

Answer 3

我必须扩展到ActionBarActivity。另外，我必须为getSupportActionBar（）更改getActionBar（）。

  getSupportActionBar().setDisplayHomeAsUpEnabled(true);
  getSupportActionBar().setHomeButtonEnabled(true);

getActionBar（）nullpointer与我的类扩展活动

3 个答案: