Is there any way to have one and only one instance of each activity?

Question

I\'m finding that in my application, the user can get quite \'nested\' in the various activities that are opened while the user is using the application.

For example

Answer 1

Yes you can demand only one instance of these activities be created, but it is generally not recommended. If you simply are concerned about history, take a look at Intent.FLAG_ACTIVITY_CLEAR_TOP.

Answer 2

This is your flag! http://developer.android.com/reference/android/content/Intent.html#FLAG_ACTIVITY_REORDER_TO_FRONT

intent.addFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT)

Note the 'addFlags'. Also note that, onCreate will not be called on this Activity when a new Intent is delivered to it. It will be delivered via the onNewIntent().

This does not ensure that there is a single instance of the Activity running. To ensure that, check this out: http://developer.android.com/guide/topics/manifest/activity-element.html#lmode

Answer 3

in Manifest Activity property you can give this parameter android:launchMode="singleInstance"

Read in more detail here http://developer.android.com/guide/topics/manifest/activity-element.html

Answer 4

Add intent Flags as

Intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK|Intent.FLAG_ACTIVITY_CLEAR_TOP); StartActivity(srcActivity.java, DesiredActivity.class);

Then at onPause() DesiredActivity

Add finish(), This did the work for me.

Answer 5

This worked for me.

Intent intent = new Intent(this, MyActivity.class);
intent.addFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
startActivity(intent);

If an instance of this Activity already exists, then it will be moved to the front. If an instance does NOT exist, a new instance will be created.

Answer 6

I wanted to have only one Instance of MainActivity, but when I add:

launchMode="singleInstance"

to my manifest a white screen appears before all of my app activities, so I removed singleInstance code from manifest. I added two public static variable of my MainActivity to MainActivity Class:

public static MainActivity mainActivity_instance = null;
public static MainActivity mainActivity_OldInstance = null;

then I added the following code to onCreate():

 if(mainActivity_instance != null)//if true, it means there was an instance of mainActivity before and it had to be closed.
        mainActivity_OldInstance = mainActivity_instance;
    mainActivity_instance = this;
 if(mainActivity_OldInstance != null)
        mainActivity_OldInstance.finish();

As you see, I finished previous instance of MainActivity just as the new Instance created!