Develop Reference

startActivity() doesn't work when app is in background (In this special case)

I'm trying to bring my app from background to foreground. In onHandleIntent() of my custom IntentService class, I have:
Intent intent = new Intent();
intent.setClass(getApplicationContext(), MainActivity.class); // Also tried with "this" instead of getApplicationContext()
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
intent.setAction(Intent.ACTION_MAIN);
intent.addCategory(Intent.CATEGORY_LAUNCHER);
startActivity(intent);
Now this code works at first sight but I found a scenario where it doesn't work. If you have the app opened and you put it to background via home button and execute startActivity() within ~5 second, there will be a delay before your app will come to foreground. This is a known implementation and you can find the topic discussed on stackoverflow. In this scenario, the app succeeded in coming from background to foreground.
If you repeat the same experiment above, but instead of waiting for the app to come to foreground, go browse (scroll, swipe, etc) around your phone (I was browsing around the google playstore). The result is that startActivity() will get called but the app will not come to the foreground.
I'm not asking for a solution but more of an explanation on why this is happening. Is this intended behavior?

Use the context of your class.
For instance :
Intent intent= new Intent(context, other.class)
Instead of getapplicationContext()

Use the code :
private void startMenuActivity() {
Intent i = new Intent(this, MainActivity.class);
i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP
| Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(i);
finish();
}

the below code works for me,
val login = Intent(applicationContext, SignInActivity::class.java)
login.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK)
login.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK)
applicationContext.startActivity(login)

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

Send application to back & bring to front

I want to develop an application where it will start on particular time & close on particular time. Similar like Alarm but not alarm application.
As per my thinking I will start an service when application first started service will check current time & particular timing to match the condition & when condition is to close application it will simply send application to background so that service will be running & when condition for wake up occurs service will bring application front.
Is this possible? If yes please give an example links or anything helpful.
Also I am trying to understand the service but it's little bit complex for me so if you have link which will help me to understand the service it will be very helpful. Thank You.
Problem Solved:
/*To close the activity/
Intent intent = new Intent(Intent.ACTION_MAIN);
intent.addCategory(Intent.CATEGORY_HOME);
intent.addCategory(Intent.CATEGORY_DEFAULT);
startActivity(intent);
MainActivity.this.finish();
OR Just finish activity;
MainActivity.this.finish();
/** To start the activity*/
Intent i = new Intent();
i.setAction(Intent.ACTION_MAIN);
i.addCategory(Intent.CATEGORY_LAUNCHER);
i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
ComponentName cn = new ComponentName(this, MainActivity.class);
i.setComponent(cn);
startActivity(i);
It worked for me still I if any one have better solution please post below.
Thank You

You can create a BroadcastReceiver to listen for time changes, and at your specified times, create an Intent to launch or to close your main Activity.

Android Launcher Shortcuts

I have made a simple punch in / punch out time clock application. I want to add the user the option of making a shortcut on the homescreen that will toggle the state of the app(time out / time in) but I don't want this shortcut to open up the app on the screen at all.
here is my setupShortcut()
private void setupShortcut() {
Intent shortcutIntent = new Intent(this, Toggle.class);
// shortcutIntent.setClassName(this, Toggle.class.getName());
shortcutIntent.putExtra(EXTRA_KEY, "ToggleShortcut");
shortcutIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
Intent intent = new Intent();
intent.putExtra(Intent.EXTRA_SHORTCUT_INTENT, shortcutIntent);
intent.putExtra(Intent.EXTRA_SHORTCUT_NAME, "ToggleShortcut");
Parcelable iconResource = Intent.ShortcutIconResource.fromContext(this, R.drawable.app_sample_code);
intent.putExtra(Intent.EXTRA_SHORTCUT_ICON_RESOURCE, iconResource);
setResult(RESULT_OK, intent);
}
Toggle.class is an activity that toggles the state for me. In the manifest I have these settings on it
<activity android:name=".Toggle" android:exported="true" android:theme="#android:style/Theme.Translucent.NoTitleBar">
As it is now I can create a shortcut on the home screen then press it. The first time I press it it starts the Toggle activity and completes it fine, but it also opens up the TimeClock activity on the screen. If I then hit the back button I go back to the home. I can now press this shortcut and it will start the Toggle activity and not change the screen. Before I added: shortcutIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP); It would open up the TimeClock activity every time. Now it is just the first time. But I want it to never show anything on the screen when the Toggle shortcut is pressed. Does anyone have any idea of how to get rid of that?

The problem with launchers is that they start Activities, whereas what you want is to start a Service so you can modify the app state in the background. It sounds like what you really want to do is make a Widget, not a launcher shortcut. You can configure the widget to have a button that sets off a Service that will toggle things in the background.

You can "more simply" make a hidden activity that will do what you want!
This activity must use transparent themes so it never shows and call finish() at the end of the onCreate() without any particular conditions.

Android: How to kill the current activity if the new activity is the same with the current one?

I know it's kinda hard to understand the question, I'm new to Android, what I mean is that:
say I have an activity A that is currently active, then I put device sleep and wake up the device, activity A still active right now.
At this time a dialog will pop up and I press "Yes", a new activity A will be created. What I concerned is that, how do I kill the old A and then create the new A?
Right now when I click "Yes" the new A is created but it's not showing correctly.

I'm not sure what are trying to achieve, but this code snippet should do what you want.
finish();
Intent intent = new Intent(this, YourActivity.class);
startActivity(intent);
A different alternative is calling
recreate();
As the documentation says: This results in essentially the same flow as when the Activity is created due to a configuration change -- the current instance will go through its lifecycle to onDestroy() and a new instance then created after it."

Try this, hope this will help.
Intent intent = new Intent(this, yourclass.class);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
finish();