Android: Starting app from ‘recent applications’ starts it with the last set of extras used in an intent

androidandroid-activityandroid-intentextras

Bit of a confusing problem for me here:

I've got a home screen widget which, when clicked, starts my main app Activity with a few extras put in the intent:

Intent start = new Intent(context, Main.class);
start.putExtra("action", "showXYZ");
start.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
context.startActivity(start);

This all works fine, it starts my activity and my activity receives the extras as expected. It processes these extras and starts another activity.

Once a user has clicked the home screen widget and started the Main activity in this way, going into the app through the 'Recent applications' method (holding down the 'home' key) starts the Main activity with the extras – causing processing to happen which I don't want (and leading to the second activity to open, rather than for the Main activity to just be shown).

Is there any work-around for this? When starting the app from the 'recent applications' method, I want to simply start the Main activity without the last set of extras.

Many thanks for the help!
r3mo

Note: I'm on android 1.5

EDIT:

Found a workaround here:
Android keeps caching my intents Extras, how to declare a pending intent that keeps fresh extras?

I'm going to timestamp the intent being set off by the widget, and check that the timestamp is recent in Main.java. If it is, i'll proceed with the processing. If not, i'll just show the Main.java activity.

Keen to hear if there are any official solutions to this.

Best Answer

As Martijn says, you can check if your application is opened using an Intent with the flag FLAG_ACTIVITY_LAUNCHED_FROM_HISTORY set, like this:

int flags = getActivity().getIntent().getFlags();       
if ((flags & Intent.FLAG_ACTIVITY_LAUNCHED_FROM_HISTORY) != 0) {
    // The activity was launched from history
}

Related Solutions

Android – How to send parameters from a notification-click to an activity

Take a look at this guide (creating a notification) and to samples ApiDemos "StatusBarNotifications" and "NotificationDisplay".

For managing if the activity is already running you have two ways:

Add FLAG_ACTIVITY_SINGLE_TOP flag to the Intent when launching the activity, and then in the activity class implement onNewIntent(Intent intent) event handler, that way you can access the new intent that was called for the activity (which is not the same as just calling getIntent(), this will always return the first Intent that launched your activity.
Same as number one, but instead of adding a flag to the Intent you must add "singleTop" in your activity AndroidManifest.xml.

If you use intent extras, remeber to call PendingIntent.getActivity() with the flag PendingIntent.FLAG_UPDATE_CURRENT, otherwise the same extras will be reused for every notification.

Android – How to make an android app return to the last open activity when relaunched

When launched via icon on the home screen, Android will always start the activity with the android.intent.action.MAIN filter in your AndroidManifest.xml, unless the application is already running (in which case it will obviously restore the activity on top of the stack).

To achieve what you described you can simply store the last visible activity in SharedPreferences and have a Dispatcher activity that starts the last activity according to the preferences.

So in every activity you want to re-start automatically:

@Override
protected void onPause() {
    super.onPause();

    SharedPreferences prefs = getSharedPreferences("X", MODE_PRIVATE);
    Editor editor = prefs.edit();
    editor.putString("lastActivity", getClass().getName());
    editor.commit();
}

And a Dispatcher activity similar to the following:

public class Dispatcher extends Activity {

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

        Class<?> activityClass;

        try {
            SharedPreferences prefs = getSharedPreferences("X", MODE_PRIVATE);
            activityClass = Class.forName(
                prefs.getString("lastActivity", Activity1.class.getName()));
        } catch(ClassNotFoundException ex) {
            activityClass = Activity1.class;
        }

        startActivity(new Intent(this, activityClass));
    }
}

Remarks

You could create a base class for the onPause override
The Dispatcher activity obviously needs to be the android.intent.action.MAIN action

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