CODEWITHSUNDEEP
android
user2700452
user2700452

Reputation: 21

confused about android example code

I'm looking over some code on the android developer's site and have a quick question about the example show here - http://developer.android.com/guide/components/fragments.html

In particular, I'm looking at this piece of code -

public static class DetailsActivity extends Activity {

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

    if (getResources().getConfiguration().orientation
            == Configuration.ORIENTATION_LANDSCAPE) {
        // If the screen is now in landscape mode, we can show the
        // dialog in-line with the list so we don't need this activity.
        finish();
        return;
    }

    if (savedInstanceState == null) {
        // During initial setup, plug in the details fragment.
        DetailsFragment details = new DetailsFragment();
        details.setArguments(getIntent().getExtras());
        getFragmentManager().beginTransaction().add(android.R.id.content, details).commit();
    }
}

What is the point of the second if statement -

if (savedInstanceState == null) {

I can't find any situation where this if statement wouldn't be true. I've tested this code by adding an else statement and setting a breakpoint in it. I could not get to that breakpoint no matter I tried. So why even bother with an if statement? Why not leave it out all together?

Upvotes: 1

Views: 68

Answers (4)

user2700452
user2700452

Reputation: 21

Apparently this was added to the example for future expansion on this code. While it has absolutely no functionality as it stands right now, if this activity were to launch another activity and get killed while the new activity had focus, this code would rebuild the activity when the user hits the back button, rather than rebuilding from scratch.

Upvotes: 0

Steve Benett
Steve Benett

Reputation: 12933

You have to look at the complete example code. With this part it makes sense.

@Override
public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    outState.putInt("curChoice", mCurCheckPosition);
}

If you start your Activity the first time the Bundle savedInstanceState will be null and the body of the if statement will be executed. If onSaveInstanceState is called, because you navigated away from the Activity, the Bundle isn't null anymore and the if body will be not executed.

Upvotes: 1

Robby Pond
Robby Pond

Reputation: 73484

If your app was paused/killed, etc and you saved state by onSaveInstanceState then savedInstanceState will contain the state of your app that you saved. Otherwise it will be null.

Upvotes: 0

Ameen
Ameen

Reputation: 2586

There are situations in which your Activity is stopped by the Android operating system. In those cases, you get a chance to save the state of your Activity by a call to [onSaveInstanceState](http://developer.android.com/reference/android/app/Activity.html#onSaveInstanceState(android.os.Bundle). If after this, your Activity is started again, it'll be passed the Bundle you created so that you can restore the state properly.

Upvotes: 1

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