sarunw sarunw - 1 month ago 17
Android Question

How to navigate up to the same parent state

From my observation from Gmail and TED app the behavior of up navigation it will navigate to parent with the same state (scroll position) not like what Google say in their doc Implement Up Navigation which like create a parent intent and start it.

I implement the code from Android sample code and all state are gone (All Extra parameters I have previously set and scroll position). What is the proper way on this ? I can't find any on Android document.

Below is the code:

public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
Intent upIntent = new Intent(this, MyParentActivity.class);
if (NavUtils.shouldUpRecreateTask(this, upIntent)) {
// This activity is not part of the application's task, so create a new task
// with a synthesized back stack.
TaskStackBuilder.from(this)
.addNextIntent(new Intent(this, MyGreatGrandParentActivity.class))
.addNextIntent(new Intent(this, MyGrandParentActivity.class))
.addNextIntent(upIntent)
.startActivities();
finish();
} else {
// This activity is part of the application's task, so simply
// navigate up to the hierarchical parent activity.
NavUtils.navigateUpTo(this, upIntent);
}
return true;
}
return super.onOptionsItemSelected(item);


}

In my case I got 3 activities say A B and C, when user navigate from A to B I put some extras and
onCreate
of B I use that extras to query data from database to populate my rows and when I navigate back from C all extras are gone and Activity B show nothing.

Answer

The "standard" behaviour for an android activity is, that a new instance of the activity is created, every time there is a new intent for this activity (see launchMode-docu here). Because of this your extras seem to be gone, if you call navigateUpTo.

In your case, I would advise to use

android:launchMode="singleTop"

for your parent activity in your AndroidManifest.xml. This way you will return to your existing activity (as long as it is on the top of the back stack of your task). This way your extras will be preserved.

I too, do not understand why this is not mentioned in the Google doc you cite, as this seems the behaviour one expects if using up-navigation.

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