Develop Reference

Best way to handle activity state

I'm making an app that shows another activity when I correctly login however in the home screen when I pressed back and then returned to the app the login activity showed.
I was able to avoid this overriding the onBackPressed this way:
public void onBackPressed()
moveTaskToBack(true);
}
Is this the best way to do it? Is there a more proper way to keep the state of the application when I exit it?

In your login activity after starting intent call finish()
finish destroy your activity and avoid to run it again automatically.

Your issue is that you kept LoginActivity in stack. so when you press back it will kill MainActivity(after login) and since LoginAcitivity still there. it will be shown again. best is to kill LoginAcitivty after starting new activity.
call this in LoginActivity:
Intent intent = new Intent(context, MainActivity.class);
startActivity(intent);
finish();

As you question I understand, you want to clear the entire history stack and start a new activity. For this, in API level 11 a new Intent Flag was added which is: Intent.FLAG_ACTIVITY_CLEAR_TASK
Just to clarify, use this:
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
For API <=10 now one can use IntentCompat class for the same. One can use IntentCompat.FLAG_ACTIVITY_CLEAR_TASK flag to clear task. So you can support pre API level 11 as well.

Launch activity from background app

I have my app running in the background and I want the app to be shown on the top(launched) of the android phone when the code below is ran. (I know the code is ran for sure)
This seems like a simple thing but I spent a couple hours on this site and everyone seems to be suggesting something like this:
Intent intent = new Intent(myActivity.this, myActivity.class);
startActivity(intent);
However, it is not bringing the app to the front and launching it.
I got it to work from a PendingIntent launched from a notification. Which I done by the code below. But I want the app to launch by itself without the user clicking on the notification.
Intent intent = new Intent(myActivity.this, myActivity.class);
PendingIntent contentIntent = PendingIntent.getActivity(this, REQUEST_CODE, intent, 0);
notification.setLatestEventInfo(this, "title", "msg", contentIntent);
I also tried:
Intent intent = new Intent("android.intent.action.MAIN");
startActivity(intent);
and flagging the intent:
intent.setFlags(Intent.FLAG_FROM_BACKGROUND);
intent.setFlags(Intent.FLAG_ACTIVITY_BROUGHT_TO_FRONT);
intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
But doesn't seem to do anything, any help appreciated.

You should be able to call your own application like this:
Intent intent = new Intent("android.intent.category.LAUNCHER");
intent.setClassName("com.your.package", "com.your.package.MainActivity");
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(intent);
Edit: Forgot to add intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

From what I understand, you want a service that is running in the background and on a certain event, you want your application's activity to come in front i.e. on the users current screen whatever he is doing. It is not advisable to let a background service launch an application without a user's action. The android developer website says
A status bar notification should be used for any case in which a
background service needs to alert the user about an event that
requires a response. A background service should never launch an
activity on its own in order to receive user interaction. The service
should instead create a status bar notification that will launch the
activity when selected by the user.
Hence, do not try to make it launch on its own.

I An not behind my laptop atm so I am nog sure, but I think you have toe pass a context object hand then do context.startactivity(intent);
Sorry for not wel formated I am at my phone atm
Hope It helps

I am clutching at straws here, but you wrote:
MyActivity is launched first, then I either navigate to another app or just hit the home screen to have my app running in the background.
So the situation is that your original Activity is NOT running in the background, when you pressed HOME it might well could have been stopped and destroyed. Your background task remained orphan and MyActivity.this is null at this point.
Try and test what does Log.i(TAG,MyActivity.this); print into LogCat.

I ended up using a pending intent and instead of stright up trying to use a intent.
Something like this: seems a lot more simple.
Intent.send(this, 0, intent);
Thanks.

Also, I’ve seen since compileSdkVersion 29 it's not possible, unless a few restrictions:
The activity started very recently.
The app called finish() very recently.
Through a PendingIntent, but only after a few seconds after the notification was sent.
The app has been granted the SYSTEM_ALERT_WINDOW permission by the user.
...
https://developer.android.com/guide/components/activities/background-starts

Intent is very slow to launch a new Activity :(

I have this piece of code for an Intent:
Intent i = new Intent();
i.setAction(Intent.ACTION_MAIN);
i.addCategory(Intent.CATEGORY_LAUNCHER);
i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK
| Intent.FLAG_ACTIVITY_RESET_TASK_IF_NEEDED);
i.setComponent(new ComponentName(packToLaunch, nameToLaunch));
startActivity(i);
This basically launches a new activity based on the package name that I pass to it. Sometimes, it takes up to 5 seconds to launch this new Activity. Is there any way to speed this process up? It even takes this long when I have an app that is still running. Please help...

It looks like Android intentionally delays launch of activity from service right after you press HOME button. (When using BACK button everything is OK.) There was even issue posted https://code.google.com/p/android/issues/detail?id=4536 however it got obsolete.
I tried to search actual implementation of the delay in Android source, but failed. You might want to check the following question as it states pretty same issue and gives some more insights: Starting an activity from a service after HOME button pressed without the 5 seconds delay

Android Launching or bringing to front another application via Intent

Im having trouble getting this to work, here´s a quick overview of the idea.
First, I cant change the logic behind this, it was a specific requirement from the customer, I realize that with any tool such as AnyCut it could be bypassed but that doesnt matter really.
My customer offers a suite of apps, the idea is that all applications bellonging to the suite would be launched from a "Dashboard app", so that I only show the Dashboard app in the main launcher and not all app icons.
Lets take two Apps to get the idea solved. The Dashboard App (A) and the Recieving App (B).
I want to establish an intent filter (I think) on app B so that whenever I go into app A, and click the app B icon the app will be either launched or started from where it let of (brought to front).
Is this even possible? If so, how can I do it? I managed to get it to launch by specifically launching one activity in the app using:
Intent i = new Intent();
i.setClassName("PACKAGE_NAME","SPECIFIC_CLASS");
startActivity(i);
But that isnt the behaviour that I want, as it always starts app B in the same spot.
Thanx in advance,
Stefano
Edit: Added some new information. I was taking a look at the DDMS.
If I launch the application from scratch through the main Android launcher the intent is exactly the same as when I leave the home button pressed and then only bring the app to front, what ever activity im in. So I was trying to reproduce, unsucsesfully until now, this intent.
INFO/ActivityManager(1292): Starting activity: Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10200000 cmp=com.example.package/.uiPackage.Activity}
This is how AnyCut does it
Intent { act=android.intent.action.VIEW flg=0x10000000 cmp=com.example.package/.uiPackage.Activity bnds=[125,242][235,360]}
Any idea how I could go about creating that exact same intent? I cant even find that flag in the Intent API.

Figured it out, this is how I did it.
Intent i = new Intent();
i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
i.setAction("android.intent.action.VIEW");
i.setComponent(ComponentName.unflattenFromString("com.example.package/com.example.package.activityName"));
startActivity(i);

I'm not quite sure I'm following the expected results you want to see, but the following would launch the app from the dashboard and remove the dashboard from the activity stack leaving the selected app running:
Intent i = new Intent();
i.setClassName("PACKAGE_NAME","SPECIFIC_CLASS");
i.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(i);
I believe this should start the app as if you were starting any other app.
Please add more information on your logic if this is not what you are looking for.

I think that when you switch activities android's default action is to sort of pause or hold the activity in its state the user left it in last. I know there is a way to make it so that the state is not saved when switching activities but I cant remember it off the top of my head.

Opening browser activity, but prevent it from being in the activity history

I'm working on an app that launches the browser activity to perform a Twitter OAuth authorization. This process uses a callback url which will re-launch the activity that started the browser activity in the first place.
My problem is that the browser pages remain in the history stack and when the user then clicks back from the preferences activity that launched the browser in the first place, they don't go back to the app's main activity, but instead are brought back to the browser. I've tried adding flags to the launching intent to prevent history and reset on clear, but it doesn't seem to work when running on my phone, only on the emulators.
Here is the code I'm using to launch the browser activity:
Intent webIntent = new Intent(Intent.ACTION_VIEW, Uri.parse(authUrl));
webIntent.addFlags(Intent.FLAG_ACTIVITY_NO_HISTORY);
webIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_WHEN_TASK_RESET);
webIntent.addFlags(Intent.FLAG_ACTIVITY_EXCLUDE_FROM_RECENTS);
ctx.startActivity(webIntent);
Anyone have any idea what might be wrong?

Set the activity flag to Intent.FLAG_ACTIVITY_CLEAR_TOP after starting it. This way, the task will be deleted form the app stack so your main activity remains the top one on every new launch:
ctx.startActivity(webIntent);
browserIntent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);

call
finish();
after
ctx.startActivity(webIntent);

Hi i have the same problem at the moment. I think the solution is to start the activity you want to return to with a special flag:
Intent intent = new Intent(this, acticityToReturnTo.getClass());
intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
intent.setFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP);
startActivity(intent);
The problem is that is does not work (on 1.6 at least).. But maybe someone finds a solution for this. I think FLAG_ACTIVITY_CLEAR_TOP is exactly what we.

I found that Intent.FLAG_ACTIVITY_NO_HISTORY works only if the browser was not running before. If I restart Android and run my app which call browser everything work well. But when I start browser before my app, browser will stay in history.
Here is related question also, but with no really working solution
How can I do that in Android. Activity -> WebBrowser -> Acrivity, but Press Back not see the WebBrowser