How to Return to a Parent Activity Correctly

How can I return to a parent activity correctly?

You declared activity A with the standard launchMode in the Android manifest. According to the documentation, that means the following:

The system always creates a new instance of the activity in the target
task and routes the intent to it.

Therefore, the system is forced to recreate activity A (i.e. calling onCreate) even if the task stack is handled correctly.

To fix this problem you need to change the manifest, adding the following attribute to the A activity declaration:

android:launchMode="singleTop"

Note: calling finish() (as suggested as solution before) works only when you are completely sure that the activity B instance you are terminating lives on top of an instance of activity A. In more complex workflows (for instance, launching activity B from a notification) this might not be the case and you have to correctly launch activity A from B.

Navigating back to Parent activity with toolbar

@Override
public boolean onOptionsItemSelected(MenuItem item)
{
    int id = item.getItemId();
    if(id == android.R.id.home)
    {
        //NavUtils.navigateUpFromSameTask(this);
          finish();
    }

    return super.onOptionsItemSelected(item);
}

Android activity go back to activity that started it instead of parent activity when pressing navigation bar back button

You should not define ActivityB as parent for ActivityA in manifest. Instead, handle onOptionsItemSelected in ActivityA like this:

public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
        case android.R.id.home:
            finish();
        }
    return super.onOptionsItemSelected(item);
    }

Is there any way to know if an activity has a parent activity or not?

Yes, getParentActivityIntent()

Obtain an Intent that will launch an explicit target activity specified by this activity's logical parent. The logical parent is named in the application's manifest by the parentActivityName attribute. Activity subclasses may override this method to modify the Intent returned by super.getParentActivityIntent() or to implement a different mechanism for retrieving the parent intent entirely.

Returns a new Intent targeting the defined parent of this activity or null if there is no valid parent.

android - refresh parent Activity when child Activity finishes

Start child activity as

startActivityForResult(intent, requestCode)

And in case on up button set result as success in child activity and in case of backpress set result as failure.

And in onActivityResult(..) of parent activity get the status and kill the parent activity in the desired case.

How to detect if a parent activity is in the back stack and can go up without creating a new instance?

I'm still not clear on what exactly you want, so I'll break this up into snippets:

If you want to launch a parent of Activity B and ensure that it isn't "launching itself", you can use the singleTop flag as noted by others to ensure that only one instance of B is ever on the top. You mentioned you don't have an issue with that, but you've listed that as an example, so just keep that in mind.

You've also mentioned that you check if the parent is A before launching Activity A. If all you want to do is actually launch the previous activity in the stack, there is no need for an Intent. Just finish your activity and it will exit the stack, showing the previous activity.

If you have a set activity that you should launch when going back, you can simply launch it with an intent. At this point, it doesn't matter what the previous activity is, because you are explicitly starting an activity for a given class. Again, you may look at the FLAG_ACTIVITY_REORDER_TO_FRONT flag to ensure that an existing activity is not recreated.

Lastly, if you have some complex logic that requires you to know the full stack history, you can always pass data through your bundle. A simple example is an arraylist of the simple class name so you know everything in the current task.

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Edit: Since you've also added that you depend on information from previous classes, I take it that you need more than just the class name.

Note that you can always pass data through the bundles so that they are retained through all subsequent activities. You can also pass all the current data by calling putExtras.

And if your entire flow is geared towards going to a child and then passing data back to a parent, consider using [startActivityForResult](https://developer.android.com/reference/android/app/Activity.html#startActivityForResult(android.content.Intent, int)). That way, you can set result codes and data and finish your activity to directly pass information to the previous activity, without launching a new intent in a forward flow manner.

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