Develop Reference

Android - Bring an activity to the front from application class

I am trying to bring an activity to the front. I found many questions similar to this but none of them actually works.
I always hold a reference to the current activity in a variable in application class. While the application is running in the background (after onPause fires), if any message arrives, I need to bring the same activity to the front and display the message. The only way I got it worked is..
Intent i = new Intent(mCurrentActivity, JoboffersActivity.class);
i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(i);
The issue I have got with this, is that it recreates the activity which I wanted to avoid. I tried singleInstance and singleTask both in the manifest. If I do not add FLAG_ACTIVITY_CLEAR_TOP, on back key press it takes me to the previous instance of the same activity. Even if I add sigleInstance it creates two instances of the same activity. If I do not add FLAG_ACTIVITY_NEW_TASK then it shows an error Calling startActivity() from outside of an Activity context requires the FLAG_ACTIVITY_NEW_TASK flag

Try to add another flag FLAG_ACTIVITY_SINGLE_TOP to your intent.
According to Android documentation, combination of this 2 flags:
i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_SINGLE_TOP);
brings the current instance of Activity to the front.
http://developer.android.com/reference/android/content/Intent.html#FLAG_ACTIVITY_CLEAR_TOP

Kill all instances of an Activity

I'm setting up Notifications in my app and I've noticed whilst testing, after clicking a new notifications (in this case the notification loads a blog details page), I have many instances of the blog details activity running (pressing back it shows each activity with the previously loaded blogs).
Is it possible in my Receiver class, so look if there is any instance of ActivityBlog already running, and if there all .finish() them all so there is only ever once instance running?
I found this but I couldn't work out a way to do it from that.

You should study activity launch modes
http://developer.android.com/guide/topics/manifest/activity-element.html#lmode
Use android:launchMode="singleTop" in element in manifest file.
You will get callback in onNewIntent() if an instance of activity is already up. Stack of your activities will be automatically updated and there wont be any need of killing activities which is consumes time and resources.
This i believe is the recommended approach.

Intent z = new Intent(Projects_Accel.this,MainActivity.class);
z.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP |
Intent.FLAG_ACTIVITY_CLEAR_TASK |
Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(z);
use this for kill all activity

Do this way
Intent intent = new Intent(this, ActivityBlog.class);
ComponentName cn = intent.getComponent();
Intent mainIntent = IntentCompat.makeRestartActivityTask(cn);
activity.startActivity(mainIntent);
NOTE:
You need to put android-support.jar in libs folder

Multiple Instances of an Activity

I am trying to show the user information on incoming-call screen, whenever there is an incoming-call. So I have a broadcast receiver listening to incoming calls, which starts the intent service, which subsequently starts an activity (with Theme Dialog).
Now, whenever there is an incoming-call, my activity dialog pops up and shows as intended.
Problem: When the activity dialog is already on the screen and incoming-call happens, there is no new activity dialog with new information. I guess that whenever there is an instance, Android does not creates the new one. So it seems like my problem is "creating multiple instances of an activity".
Please note that I am starting an activity from an intent service using FLAG_NEW_TASK.

Google Doc says :
FLAG_ACTIVITY_NEW_TASK
"When using this flag, if a task is already running for the activity
you are now starting, then a new activity will not be started;
instead, the current task will simply be brought to the front of the
screen with the state it was last in."
So, if you want to start a new fresh activity then simply not use this flag only, you should use it with FLAG_ACTIVITY_CLEAR_TASK for the desired result.
For Example:
// Sets the Activity to start in a new, empty task
notifyIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK |
Intent.FLAG_ACTIVITY_CLEAR_TASK);
If the above solution is not what you needed, then have a look at
android:launchMode attribute, declare this attribute with the desired options (i.e. as per your need) in activity tag of manifest file.
Hope this will solve the problem.

Use flag FLAG_ACTIVITY_MULTIPLE_TASK which according to the documentation :
Used in conjunction with FLAG_ACTIVITY_NEW_TASK to disable the behavior of bringing an existing task to the foreground. When set, a new task is always started to host the Activity for the Intent, regardless of whether there is already an existing task running the same thing.
Using this flag along with FLAG_ACTIVITY_NEW_TASK will cause each activity instance to be created as a separate task and thus you can have different dialog pop ups.

Simply add following flags to your Intent .
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK
| Intent.FLAG_ACTIVITY_EXCLUDE_FROM_RECENTS
| Intent.FLAG_ACTIVITY_MULTIPLE_TASK);

Android activity flag issue

I have my launcher activity flag set to singleTop.
when I launch activity from notification bar (with FLAG_ACTIVITY_NEW_TASK in receiver), new activity is created and the previous one is not used.
What can be done to have only one activity in stack?
Edit:
intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_NEW_TASK);`
in receiver, seem to be working

use Intent.FLAG_ACTIVITY_CLEAR_TOP

Try to learn use of these different flags. use the link below, it will ne helpful.
http://developer.android.com/reference/android/content/Intent.html#FLAG_ACTIVITY_NEW_TASK

I had to use
Intent.FLAG_ACTIVITY_SINGLE_TOP | Intent.FLAG_ACTIVITY_NEW_TASK
"Intent.FLAG_ACTIVITY_CLEAR_TOP |Intent.FLAG_ACTIVITY_NEW_TASK" makes launched activity behaves differently. Whenever I launch activity form history It always calls onNewIntent

Cannot set both FLAG_ACTIVITY_SINGLE_TOP and FLAG_ACTIVITY_CLEAR_TOP in one intent?

I'm using flag FLAG_ACTIVITY_SINGLE_TOP and FLAG_ACTIVITY_CLEAR_TOP to go back to my previous "standard" activity. I use FLAG_ACTIVITY_SINGLE_TOP to prevent re-creating a new instance. But what I found is that the flag FLAG_ACTIVITY_SINGLE_TOP is neglected and the activity is finished and re-created.
Here is what I found in docs. FLAG_ACTIVITY_CLEAR_TOP: It says that you can add FLAG_ACTIVITY_SINGLE_TOP when using FLAG_ACTIVITY_CLEAR_TOP to prevent "finish - recreate".
Here is another doc. FLAG_ACTIVITY_CLEAR_TOP:
Note: If the launch mode of the designated activity is "standard", it too is removed from the stack and a new instance is launched in its place to handle the incoming intent. That's because a new instance is always created for a new intent when the launch mode is "standard".
Did I misunderstand the first doc?

The documentation suggests that FLAG_ACTIVITY_CLEAR_TOP is all you need to set. But you actually HAVE to set both to prevent the activity from being created again.
This did the trick in my case: (Main being the activity that I wanted to return to)
Intent tabIntent = new Intent(this, Main.class);
tabIntent.setFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP | Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(tabIntent);

This one could be helpful: Android Intent.FLAG_ACTIVITY_SINGLE_TOP AND Intent.FLAG_ACTIVITY_CLEAR_TOP

Check this one.
Intent.FLAG_ACTIVITY_RESET_TASK_IF_NEEDED|Intent.FLAG_ACTIVITY_SINGLE_TOP)