When to call openDrawer() (or any other animation) to make it visible on startup?

Issue

I want my app to show the side navigation drawer as soon as the main activity is created. My code works fine - user launches app and gets the open drawer - but I'd like to actually see the side drawer sliding from the left; instead, I find the drawer fully opened.

At what point should I call openDrawer()? Have tried calling from:

• main activity OnCreate;
• similar points in the fragment hosted by the drawer.

I could try OnPrepareOptionsMenu, but I think it gets called more than once during the activity lifecycle. I also tried OnStart() and I fear my options are over. Any idea? I'm sure this is pretty simple but I can't figure out.

Edit: I realize I wasn't so clear with my first exposition of the question (@Biu). I'm talking about a purely graphical issue here. The point is:

• I have something to happen at startup; in my case we're speaking about the nav drawer sliding into the main screen, but it could be any animation I think;

• In my case, one could just call:

  protected void OnCreate(Bundle b) {
  ...
  DrawerLayout.openDrawer()
  }
  

• The above solution works well. The issue I'm talking about is graphical; with the above code you launch the app and find the main activity covered with an already-opened drawer. Instead, I'd like the user to have clue of what is happing, to see where the panel came from; in other words, to see the opening animation.

So my question is: when should I call openDrawer()? The main Activity onCreate isn't quite right, because the animation ends before the user gets to see something on screen.

I thought that the wish of having something start when all is loaded would be more common.

Solution

@benjosantony suggests that you should open your drawer at onResume, however it's not guaranteed that the activity will be visible at that time:

onResume is not the best indicator that your activity is visible to the user; Use onWindowFocusChanged(boolean) to know for certain that your activity is visible to the user

You'd think that you can just use onWindowFocusChanged and be done, but you can't. There's still the transition animation which breaks (at least for me) the drawer's animation..

For API 21+:
There's onEnterAnimationComplete where you can open your drawer and see the animation properly. However 21+ is a requirement that's just too big..

For lower APIs:
The only possible way I can think of is removing the activity's animation with a theme adjustment:

<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
    <item name="android:windowAnimationStyle">@null</item>
</style>

And opening the drawer like so:

private static final String DRAWER_STATE = "mDrawerOpened";
private DrawerLayout mDrawer;
private ListView mDrawerList;
private boolean mDrawerOpened;

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

    mDrawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    mDrawerList = (ListView) findViewById(R.id.left_drawer);
}

@Override
public void onWindowFocusChanged(boolean hasFocus) {
    super.onWindowFocusChanged(hasFocus);
    if (!mDrawerOpened && hasFocus) {
        mDrawer.openDrawer(mDrawerList);
        mDrawerOpened = true;
    }
}

@Override
protected void onSaveInstanceState(@NonNull Bundle outState) {
    super.onSaveInstanceState(outState);
    outState.putBoolean(DRAWER_STATE, mDrawerOpened);
}

@Override
protected void onRestoreInstanceState(@NonNull Bundle savedInstanceState) {
    super.onRestoreInstanceState(savedInstanceState);
    mDrawerOpened = savedInstanceState.getBoolean(DRAWER_STATE);
}

This will animate the drawer only when the activity is started.

The boolean value is saved when your activity is destroyed abnormally, e.g. rotation or need for system resources.

If you don't like setting the instanceState you can use SharedPreferences as @Biu suggested, however IMO that wouldn't be the proper solution as android already provides tools for that, there's no need to re-invent the bike.

Answered By - Simas