TransactionTooLargeException crashes on Nougat

I was testing my app on Android Nougat, and it crashed when I try to move from one Activity to another. I saw this in the log: java.lang.RuntimeException: android.os.TransactionTooLargeException: data parcel size 700848 bytes.

Actually, the platform has been printing warning log about this for a while, but let's be honest, who has time to read all the logs? Nougat (API 24) throws TransactionTooLargeExceptions as RuntimeExceptions, so we cannot ignore that any more.

onSaveInstanceState

Turns out I was saving a big list of search results during onSaveInstanceState to persist them over rotation. Time to move that to a Loader!

But what is the limit?

But now I'm curious: What is the limit? I wrote a sample app to find out.

public class MainActivity extends Activity {
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    Intent intent = new Intent(this, AnotherActivity.class);
    startActivity(intent);
  }

  @Override
  protected void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);

    int length = 1000;
    Uri uri = getIntent().getData();
    if (uri != null) {
      try {
        length = Integer.parseInt(uri.getLastPathSegment());
      } catch (NumberFormatException e) {
      }
    }

    byte[] data = new byte[length];
    outState.putByteArray("data", data);
  }
}

To try different sizes, I start the app like this:

adb shell am start \
  -a android.intent.action.View \
  -n com.sqisland.tutorial.transcation_too_large/.MainActivity \
  -d 700000

This launches MainActivity, which immediately goes to AnotherActivity. When that happens, the system calls onSaveInstanceState, which tries to stash away a byte array of the length specified in the adb command, retrieved by getIntent().getData(). This way, I can try different numbers without recompiling and redeploying the app.

I did a binary search on a Nougat emulator and my Nexus 9. The limit is slightly different, but it hovers around 500000. That is not a small number, but not too hard to exceed if you try to store data rather than state.