如何使操作栏在导航抽屉的两种状态下显示图标而没有标题？

Question

I am trying to get my Action Bar to display an icon and not display any title while both states of the Navigation Drawer (open and closed) I read the documentation on developers android about how to modify the contents of the Action Bar when the drawer is visible. As the page said, I created an instance of ActionBarDrawerToggle and set the icon and set title to null. But still I am not able to see any icon and the app title appears as soon as I draw out the Navigation drawer. The following is the code I have used in onCreate of my activity

 mToggle = new ActionBarDrawerToggle(
            this,
            drawerLayout,
            R.string.drawer_open_or_close,
            R.string.drawer_open_or_close) {

        /** Called when a drawer has settled in a completely closed state. */
        public void onDrawerClosed(View view) {
            super.onDrawerClosed(view);
            getActionBar().setTitle(R.string.drawer_open_or_close);
            getActionBar().setIcon(R.drawable.icon_144);
            invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
        }

        /** Called when a drawer has settled in a completely open state. */
        public void onDrawerOpened(View drawerView) {
            super.onDrawerOpened(drawerView);
            getActionBar().setTitle(R.string.drawer_open_or_close);
            getActionBar().setIcon(R.drawable.icon_144);
            invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
        }
    };

As you can see, I have set the Action bar title to R.string.drawer_open_or_close , which is an empty string, during both completely open and completely closed state. I have set the app icon in both cases as well. What am I missing here?

Edit: I had forgotten to set the drawer toggle as DrawerListener , which I did

drawerLayout.setDrawerListener(mToggle);

Now when I open Navigation drawer, the app force closes and the log cat says java.lang.NullPointerException at

getActionBar().setTitle(R.string.drawer_open_or_close);

Edit 2: I guess we cannot give a null string as title

LogCat:

01-31 16:01:45.335  13944-13944/com.example.android.effectivenavigation E/AndroidRuntime﹕ FATAL EXCEPTION: main
    java.lang.NullPointerException
            at com.example.android.handsfree.MainPage$1.onDrawerOpened(MainPage.java:79)
            at android.support.v4.widget.DrawerLayout.dispatchOnDrawerOpened(DrawerLayout.java:656)
            at android.support.v4.widget.DrawerLayout.updateDrawerState(DrawerLayout.java:616)
            at android.support.v4.widget.DrawerLayout$ViewDragCallback.onViewDragStateChanged(DrawerLayout.java:1627)
            at android.support.v4.widget.ViewDragHelper.setDragState(ViewDragHelper.java:873)
            at android.support.v4.widget.ViewDragHelper$2.run(ViewDragHelper.java:335)
            at android.os.Handler.handleCallback(Handler.java:730)
            at android.os.Handler.dispatchMessage(Handler.java:92)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:5162)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:525)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:756)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:572)
            at de.robv.android.xposed.XposedBridge.main(XposedBridge.java:132)
            at dalvik.system.NativeStart.main(Native Method)

Answer 1

I don't know if this is the best way but I ended up using a custom toolbar and then just manipulating the icon and title directly with findViewById() . I use a common toolbar that I include in each of my activity layouts.

    <ImageView
        android:id="@+id/toolbarLogo"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="center" 
        android:src="@drawable/logo"
        android:adjustViewBounds="true"
        android:padding="2dp"
        android:visibility="gone"
        />
    <TextView 
        android:id="@+id/toolbarTitle"
        android:textAppearance="@android:style/TextAppearance.Theme"
        android:textColor="@color/titleTextColor"
        android:textSize="18sp"  
        android:textStyle="bold"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"  
        android:singleLine="true"  
        />
</android.support.v7.widget.Toolbar>

Then I set what I need with:

    // Set the custom toolbar
    android.support.v7.widget.Toolbar toolbar = (android.support.v7.widget.Toolbar) findViewById(R.id.toolbar);
    if (toolbar != null) {
        setSupportActionBar(toolbar);
        toolbar.setTitle("");
    }

    TextView title = (TextView) findViewById(R.id.toolbarTitle);
    title.setText(getString(R.string.app_long_name));
    title.setTextColor(getResources().getColor(R.color.colorPrimary));

Hopefully that gives you some ideas.