NavigationDrawer icon not showing up

问题

I am implementing a very simple example of NavigationDrawer. The example works fine, but I have a strange problem. The icon for NavigationDrawer (generally ic_drawer) does not show up in the ActionBar. I have tried using different icon images, but didn't achieved the desired result. Here's the code. The project has only one activity named MainActivity.java.

public class MainActivity extends Activity {

private DrawerLayout mDrawerLayout;
private ListView mListView;
private ActionBarDrawerToggle mDrawerToggle;
private String[] array = new String[] { "Hello", "hola", "namaste",
        "salaam" };

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

    mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer);
    mListView = (ListView) findViewById(R.id.list);

    getActionBar().setDisplayHomeAsUpEnabled(true);
    ArrayAdapter<String> adapter = new ArrayAdapter<String>(
            getApplicationContext(),
            android.R.layout.simple_dropdown_item_1line, array);
    mListView.setAdapter(adapter);
    mListView.setOnItemClickListener(new OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> arg0, View arg1, int arg2,
                long arg3) {
            Toast.makeText(getApplicationContext(), array[arg2],
                    Toast.LENGTH_SHORT).show();

        }
    });

    mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout,
            R.drawable.ic_drawer, R.string.open, R.string.close) {
        @Override
        public void onDrawerClosed(View drawerView) {
            // TODO Auto-generated method stub

            invalidateOptionsMenu();
        }

        @Override
        public void onDrawerOpened(View drawerView) {
            // TODO Auto-generated method stub

            invalidateOptionsMenu();
        }
    };
    mDrawerLayout.setDrawerListener(mDrawerToggle);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // TODO Auto-generated method stub

    if (mDrawerToggle.onOptionsItemSelected(item))
        return true;
    return super.onOptionsItemSelected(item);
}

}

And if I comment out the line with code getActionBar().setDisplayHomeAsUpEnabled(true);, the code stops working, meaning NavigationDrawer does not open.

For reference, the xml layout for this activity is:

activity_main.xml

<android.support.v4.widget.DrawerLayout 
xmlns:android="http://schemas.android.com/apk/res/android"
        android:id="@+id/drawer"
        android:layout_width="match_parent"
        android:layout_height="match_parent" >

    <TextView
        android:id="@+id/frame"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="change aaaega, hum laaenge" />

    <ListView
        android:id="@+id/list"
        android:layout_width="240dp"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:choiceMode="singleChoice" />

</android.support.v4.widget.DrawerLayout>

Any suggestions ?

Thanks.

回答1:

Include this part of code in your program,

@Override
    protected void onPostCreate(Bundle savedInstanceState) {
        super.onPostCreate(savedInstanceState);
        // Sync the toggle state after onRestoreInstanceState has occurred.
        mDrawerToggle.syncState();
    }

    @Override
    public void onConfigurationChanged(Configuration newConfig) {
        super.onConfigurationChanged(newConfig);
        mDrawerToggle.onConfigurationChanged(newConfig);
    }


    @Override
    public boolean onOptionsItemSelected(MenuItem item) {

        // call mDrawerToggle.onOptionsItemSelected(), if it returns true
        // then it has handled the app icon touch event

        if (mDrawerToggle.onOptionsItemSelected(item)) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

来源：https://stackoverflow.com/questions/23331512/navigationdrawer-icon-not-showing-up