Why does my Java object reference an old activity after orientation change?

Question

Background:

I have a FragmentActivity that uses a DrawerLayout. I created a class called NavDrawerManager to abstract out the code for dealing with the drawer layout. To construct this object, I need to pass in and keep a reference to an Activity. I use this activity reference to call findViewById(), and I also use the activity as a context when creating a list adapter, etc. I keep a reference to a NavDrawerManager object in my activity so I can perform callbacks and operations on the drawer layout.

UPDATE: Per Xaver's suggestion, I switched to extend FragmentActivity into a NavDrawerActivity. Instead of having a NavDrawerManager object in my activity, the superclass handles the nav drawer code. See updated code.

Issue:

Everything works fine until I change orientations. After changing orientations, it appears that my NavDrawerActivity still references the old layout. I say this because I have a progress bar and a couple of buttons in the DrawerLayout that I am attempting to update, but they don't reflect the updates.

When I call Activity.findViewById() to get the progress bar and make it visible, it doesn't show any changes, nor do any of the changes to the buttons show. Note: Activity.findViewById() does not return null. However, if I do the same things before changing orientation, the progress bar and buttons show the appropriate changes.

Code:

NavDrawerActivity:

public class NavDrawerActivity extends LowProfileFragmentActivity {
    private DrawerLayout mDrawerLayout;
    private ActionBarDrawerToggle mDrawerToggle;

    private ExpandableListView mDrawerList;
    private NavDrawerAdapter mListAdapter;

    @Override
    protected void onPostCreate(Bundle savedInstanceState) {
        super.onPostCreate(savedInstanceState);
        mDrawerToggle.syncState();
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        mDrawerToggle.onOptionsItemSelected(item);
        return super.onOptionsItemSelected(item);
    }

    //Called via subclass after setContentView    
    protected void setupNavDrawer() {
        initDrawerLayout();
        initDrawerList();
        setButton1();
        setButton2();
    }

    private void initDrawerLayout() {
        mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
        mDrawerToggle = getActionBarDrawerToggle();
        mDrawerLayout.setDrawerListener(mDrawerToggle);
    }

    private void initDrawerList() {
        mDrawerList = (ExpandableListView) mDrawerLayout
                .findViewById(android.R.id.list);

        mListAdapter = getNavDrawerAdapter();
    }

    private ActionBarDrawerToggle getActionBarDrawerToggle() {
        return new ActionBarDrawerToggle(this, mDrawerLayout,
                R.drawable.ic_navigation_drawer, 0, 0) {

            public void onDrawerClosed(View view) {

            }

            public void onDrawerOpened(View view) {

            }
        };
    }


    public void setDrawerLoading(boolean loading) {
        ProgressBar progressBar = (ProgressBar) mDrawerLayout
                .findViewById(R.id.progress_bar);
        Button button1 = (Button) this.findViewById(R.id.button1);
        Button button2 = (Button) this
                .findViewById(R.id.button2);

        /* None of the below changes appear after changing orientation */
        if (loading) {
            button1.setEnabled(false);
            button2.setEnabled(false);
            progressBar.setVisibility(View.VISIBLE);
        } else {
            progressBar.setVisibility(View.GONE);
            button1.setEnabled(true);
            button2.setEnabled(true);
        }
    }

    private void setButton1() {
        Button button1 = (Button) this.findViewById(R.id.button1);
        button1.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                //do something
            }

        });
    }

    private void setButton2() {
        Button button2 = (Button) this
                .findViewById(R.id.button2);
        button2.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                //do something
            }

        });
    }
}

ExampleActivity:

public class ExampleActivity extends NavDrawerActivity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        initUI();
    }

    private void initUI() {
        setContentView(R.layout.activity_sift);

        // Call the superclass method to set up the nav drawer
        setupNavDrawer();
    }
}

AndroidManifest.xml:

<activity
    android:name="com.example.app.ExampleActivity"
    android:label="@string/app_name"
    android:launchMode="singleTop"
    android:theme="@style/AppTheme" >
    <intent-filter>
        <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
    </intent-filter>
</activity>

Answer 1

Wouldn't it be easier if you implemented a NavDrawerActivity instead of a NavDrawerManager? Generally things like this should be avoided. The UI should be handled solely by the Fragments or Activities themselves.

I understand why you would want to create such a NavDrawerManager, simply to make the whole thing reusable and a lot of abstraction is great, but when it is overdone it can become a problem. Don't focus so much on everything being perfectly abstracted and according to OOP standards. There is nothing wrong with an Activity having both a NavigationDrawer and hiding the notification bar. And if you already have an Activity that implements one of those two things you should extend it. Your only other option would be to reimplement the same behaviour in a second Activity and that would pretty much defeat the purpose of abstraction.

---

EDIT: I have refactored and improved your code, you really should not have so many different methods for everything, all the setup belongs in onCreate(), that you write extra methods for each step just introduces the possibility for additional errors. Try this:

public abstract class NavDrawerActivity extends LowProfileFragmentActivity {

    private ActionBarDrawerToggle drawerToggle;
    private DrawerLayout drawerLayout;
    private ProgressBar progressBar;
    private Button button1;
    private Button button2;

    private ExpandableListView drawerList;
    private NavDrawerAdapter drawerListAdapter;

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

        this.drawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
        this.drawerToggle = new ActionBarDrawerToggle(this, this.drawerLayout, R.drawable.icon_drawer, R.string.drawer_open, R.string.drawer_close);
        this.drawerLayout.setDrawerListener(this.drawerToggle);

        this.drawerList = (ExpandableListView) this.drawerLayout.findViewById(android.R.id.list);
        this.progressBar = (ProgressBar) this.drawerLayout.findViewById(R.id.progress_bar);

        this.button1 = (Button) findViewById(R.id.button1);
        this.button1.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                //do something
            }
        });

        this.button2 = (Button) findViewById(R.id.button2);
        this.button2.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                //do something
            }
        });

        this.drawerListAdapter = new NavDrawerAdapter(...);
        this.drawerList.setAdapter(this.drawerListAdapter);
    }

    protected abstract int getLayout();

    @Override
    protected void onPostCreate(Bundle savedInstanceState) {
        super.onPostCreate(savedInstanceState);
        this.drawerToggle.syncState();
    }

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

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        return this.drawerToggle.onOptionsItemSelected(item) || super.onOptionsItemSelected(item);
    }

    public void setDrawerLoading(boolean loading) {
        this.button1.setEnabled(!loading);
        this.button2.setEnabled(!loading);
        this.progressBar.setVisibility(loading ? View.VISIBLE : View.GONE);
    }
}

As you can see I use an abstract method called getLayout() to pass the correct layout to setContentView(). getLayout() has to be implemented by all Activities which extend the NavDrawerActivity therfore giving the sub Activities control over the used layout.

As such your ExampleActivity should look like this:

public class ExampleActivity extends NavDrawerActivity {

    @Override
    protected int getLayout() {
        return R.layout.activity_sift;
    }
}

I tested everything and it's working for me.