Develop Reference

startActivity opens last app in background instead of needed activity

I got an app which can receive an event (which is basically a message from a service in the background), and when it does, I am invoking this code:
Intent dialogIntent = new Intent(this, MainActivity.class);
dialogIntent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
dialogIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(dialogIntent);
This code is supposed to return the app to the front so the user can handle the event.
This code works only if the app I'm working on was also the last app the user has been in. The code doesn't work in these scenarios:
1) The user has paused the app, opened another app and then paused it too so the 2nd app is the last in the background - in which case the last app will always open, even though I'm starting my MainActivity. For example, if I've moved my app to the background, opened Android's settings and then an event is received, the Android's settings screen will open instead of my app.
2) The user is inside another app. In which case, the app won't be brought to the front at all.
How can I made the specific app to be resumed from the background no matter what?

Use launcher category as below:
Intent resumeIntent = new Intent(context, MainActivity.class);
resumeIntent.setAction(Intent.ACTION_MAIN);
resumeIntent.addCategory(Intent.CATEGORY_LAUNCHER);
startActivity(resumeIntent);
Also add android:launchMode="singleTop" in the manifest of your activity.

You can add android:launchMode="singleTop" in the manifest for the Activity.

How to change main activity in Android programmatically

Is it possible to create two entry points to an application in Android, I mean can I switch the main activity programmatically?

Every exported activity is a potential entry point into your app; a foreign app can start any of them with an intent. (An intent-filter comes with an implicit android:export.) You can however only have one entry point that the launcher will respect. To simulate a second launch-point, either
Provide a completely separate app with the purpose of starting one of your exported activities, or
Give your 'launch' activity the sole purpose of immediately starting one or another activity based on some logic (a saved preference, a phase-of-moon calculation, anything).

check this one below
Intent intent = new Intent(Intent.ACTION_MAIN);
intent.addCategory(Intent.CATEGORY_LAUNCHER);
intent.setComponent(new ComponentName(packageName,mainActivity));
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
ctx.startActivity(intent);

I think you are talking about launching activity decision based on some events, then you need to add a broadcast receiver, like by clicking on app icon on launcher if you want to start Activity1. then add intent filters to this activity Action_MAIN and ACTION_LAUNCHER, if you want to start Activity2 on phone boot up, then add filter to this activity, BOOT_COMPLETED.

If you are talking about to launch other apps from your apps then this can be the code:
Intent intent = new Intent(Intent.ACTION_MAIN);
intent.addCategory(Intent.CATEGORY_LAUNCHER);
intent.setComponent(new ComponentName(packageName,mainActivity));
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
ctx.startActivity(intent);

Reopen activity directly after finishing a phone call

After I make a call with phone call intent and finish the call, the phone opens calls log instead of directly reopen the app activity which launches the call intent.
How do I skip going to the call log? After finishing the call I want the phone to come back to my app activity?

launch/reopen the previous activity and set flag Intent.FLAG_ACTIVITY_SINGLE_TOP to the intent.
if this flag set, the activity will not be launched if it is already running at the top of the history stack.

You can watch the Broadcast of android.intent.action.PHONE_STATE and for the extra EXTRA_STATE. If it is EXTRA_STATE_IDLE the call is finished and you can implement the logic to reopen your app

Tried this to reopen app but the app crash
Intent i = new Intent("android.intent.action.MAIN");
i.setComponent(new ComponentName("com.muaz", "HantarSMS") );
i.addCategory("android.intent.category.LAUNCHER");
startActivity(i);

Activity not being reused

I have an odd issue with my application.
I start the application and the activity shows ok.
I then press the home key so that the activity goes into the background. I can see the onPause() method being called.
The application's service then creates a notification which shows on the status bar.
I then click on the notification and the activity is shown and I see that the onResume() method is called.
I then press the home key and the activity goes into the background. I can see the onPause() method being called.
If I now start the application by clicking on the applications icon I see that a new instance of the activity is created rather than using the paused instance.
If I press the home key again the new activity goes into the background.
Starting the application by clicking on the applications icon I see another new instance of the activity is created.
Pressing the back button at the point destroys each activity in return.
What I want to happen is that a single instance of the activity be used.
Any ideas?

Just use the same intent filters as android uses when launches the app:
final Intent notificationIntent = new Intent(context, MessageListActivity.class);
notificationIntent.setAction(Intent.ACTION_MAIN);
notificationIntent.addCategory(Intent.CATEGORY_LAUNCHER);
As the intent you created to open your activity from notification bar is the same as android used for launching your app, the previously opened activity will be shown instead of creating a new one.

You should look at the different launch modes for Android activities. this should help. Launch modes can be set in the androidmanifest.xml file. I think your solution would be to use the 'singleTop' launch mode.

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.