Force application to restart on first activity

Question

For an unknown reason, I can't get my application leaving properly so that when I push the home button and the app icon again, I resume where I was in the app. I would like to force the application to restart on the first Activity.

I suppose this has something to do with onDestroy() or maybe onPause() but I don't know what to do.

Matronage

Answer 1

Here is an example to restart your app in a generic way by using the PackageManager:

Intent i = getBaseContext().getPackageManager()
             .getLaunchIntentForPackage( getBaseContext().getPackageName() );
i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_CLEAR_TASK);
startActivity(i);

Forgery

It help me.Thanks. I used like that,"try { Intent i; i = getBaseContext().getPackageManager() .getLaunchIntentForPackage( getBaseContext().getPackageName() ); i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP); startActivity(i); } catch (NameNotFoundException e) { e.printStackTrace(); } – Petrick

One problem with this approach. new activity's onCreate is called before old activity stack gets onDestroy – Utu

@AAverin: how can I get onDestroy to be called before onCreate? – Lauro

Probably related with above issue: this does not seem to be working from child activities. I have used it in a PreferenceActivity called with FLAG_ACTIVITY_NO_HISTORY, and I am not getting the expected behavior from a full restart (I believe some of my instanced booleans are not being cleared exactly because onCreate comes up before onDestroy on the Launcher activity). – Mournful

this works great for me, except when I then navigate to another activity, press the home button, then launch my app again through the icon, I'm now brought to a new instance of my main activity on top of my back stack, since mine is set to a launchMode of "singleTop" See my answer below for how I added in a fix for this – Boorman

not working, just resume in launch activity , the application class not reset – Codding

Are static variables/properties reinitialized here as well? – Endways

But if i call this method from my tests(espresso) for example, how i can correct to restart my app? – Avesta

Thanks for the solution i was looking so long..works fine – Marja

Use flags as Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_CLEAR_TASK, this works great and clears the activity stack as well. – Viridity

Answer 2

The solution marked as 'answer' works but has one disadvantage that was critical for me. With FLAG_ACTIVITY_CLEAR_TOP your target activity will get onCreate called before your old activity stack receives onDestroy. While I have been clearing some necessary stuff in onDestroy I had to workaroud.

This is the solution that worked for me:

public static void restart(Context context, int delay) {
    if (delay == 0) {
        delay = 1;
    }
    Log.e("", "restarting app");
    Intent restartIntent = context.getPackageManager()
            .getLaunchIntentForPackage(context.getPackageName() );
    PendingIntent intent = PendingIntent.getActivity(
            context, 0,
            restartIntent, Intent.FLAG_ACTIVITY_CLEAR_TOP);
    AlarmManager manager = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE);
    manager.set(AlarmManager.RTC, System.currentTimeMillis() + delay, intent);
    System.exit(2);
}

The idea is to fire a PendingIntent via AlarmManager that will be invoked a bit later, giving old activity stack some time to clear up.

Utu

Why don't you just call the Activity's finish() method instead of System.exit? The doc says "Call this when your activity is done and should be closed." – Lauro

I just realized that it's due to the method being static, thus not being able to call any non-static methods such as finish. I just made restart non-static, and replaced the System.exit call instead. – Lauro

And after testing, I found out that using finish() causes my app to hang on startup, while System.exit works fine ... – Lauro

agree with previous comment. I've used PendingIntent.FLAG_CANCEL_CURRENT instead of Intent.FLAG_ACTIVITY_CLEAR_TOP to remove warning – Britneybritni

Answer 3

if you want to always start at the root you want to set android:clearTaskOnLaunch to true on your root activity

Enmesh

yeah I tried that but then when i click the icon again it seems to call on Resume instead of onCreate... which means I get a screen without any of my methods starting – Matronage

Or add the flag Intent.FLAG_ACTIVITY_CLEAR_TASK programmatically to the Intent. – Metallophone

Answer 4

android:clearTaskOnLaunch="true"
android:launchMode="singleTask"

Use this property in manifest file in starting class (first activity).

Factitive

Answer 5

Does FLAG_ACTIVITY_CLEAR_TOP do what you need to do?

Intent i = new Intent(getBaseContext(), YourActivity.class);
            i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
            startActivity(i);

Permissible

Answer 6

FLAG_ACTIVITY_CLEAR_TOP didn't work for me because I had to support 2.3.3. My first solution was:

Intent intent = context.getPackageManager().getLaunchIntentForPackage(context.getPackageName());
    intent.addFlags(Build.VERSION.SDK_INT >= 11 ? Intent.FLAG_ACTIVITY_CLEAR_TASK : Intent.FLAG_ACTIVITY_CLEAR_TOP);
context.startActivity(intent);

This almost works, but not quite.

Since I have a base Activity, I added a kill broadcast that closes all my running activities.

public abstract class BaseActivity extends AppCompatActivity {

    private static final String ACTION_KILL = "BaseActivity.action.kill";
    private static final IntentFilter FILTER_KILL;
    static {
        FILTER_KILL = new IntentFilter();
        FILTER_KILL.addAction(ACTION_KILL);
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        registerReceiver(killReceiver, FILTER_KILL);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        unregisterReceiver(killReceiver);
    }

    private final BroadcastReceiver killReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            finish();
        }
    };

    public void killApp(){
        sendBroadcast(new Intent(ACTION_KILL));
    }
}

All of my activities extend from this class, so

((BaseActivity)getActivity()).killApp();
startActivity(new Intent(getActivity(), StartActivity.class));

restarts the app. Tested on genymotion v10, v16, v21 and Nexus 5 with v22.

Edit: this does not remove an activity if it is destroyed at the time of sending the intent. I'm still looking for a solution.

Volar

Answer 7

The following code is work for me, it can restart full app perfectly!

Intent mStartActivity = new Intent(context, StartActivity.class);
int mPendingIntentId = 123456;
PendingIntent mPendingIntent = PendingIntent.getActivity(context,mPendingIntentId,    mStartActivity, PendingIntent.FLAG_CANCEL_CURRENT);
AlarmManager mgr = (AlarmManager)context.getSystemService(Context.ALARM_SERVICE);
mgr.set(AlarmManager.RTC, System.currentTimeMillis() + 100, mPendingIntent);
System.exit(0);

Carrack

What is the meaning of the value of mPendingIntentId? Looks like a particularly magical number - is it just an arbitrary int? – Cornall

It's just an arbitrary number, you can use any random integer. It's a message number in PendingIntent class. – Carrack

Answer 8

Marc's answer works great, except in my case where my main activity has a launchMode of singleTop. Once I run this intent and then navigate to new Activities and press the home button on the device, then launch my app again from the app icon, I end up creating a new instance of the main Activity, with my previous activity on the back stack.

According to this question it's because the intents don't match. Looking at adb dumpsys activity, I see that from my standard android launcher, the package is null, whereas when I do as Marc suggests, the intent package is the name of my package. This difference causes them to not match and to start a new instance when the app icon is tapped again and the main activity isn't on top.

However, on other launchers, like on Kindle, the package is set on the launcher intent, so I needed a generic way to handle launchers. I added static methods like such:

static boolean mIsLaunchIntentPackageNull = true;    

public static boolean isLaunchIntent(Intent i) {
    if (Intent.ACTION_MAIN.equals(i.getAction()) && i.getCategories() != null
            && i.getCategories().contains(Intent.CATEGORY_LAUNCHER)) {
        return true;
    }

    return false;
}

public static void handleLaunchIntent(Intent i) {
    if (isLaunchIntent(i)) {
        if (i.getPackage() != null) {
            mIsLaunchIntentPackageNull = false;
        }
        else {
            mIsLaunchIntentPackageNull = true;
        }
    }
}

with a go home mechanism like this:

    Intent intentHome = appContext.getPackageManager()
            .getLaunchIntentForPackage( appContext.getPackageName());
    intentHome.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);

    // need to match launcher intent exactly to avoid duplicate activities in stack
    if (mIsLaunchIntentPackageNull) {
        intentHome.setPackage(null);
    }
    appContext.startActivity(intentHome);

then in the main activity defined in my manifest, I added this line:

public void onCreate(Bundle savedInstanceState) {
    [class from above].handleLaunchIntent(getIntent());

this works for me on kindle and my phone, and lets me properly reset the app w/o adding another instance of the main activity.

Boorman

Answer 9

You can use Jake Wharton's lib ProcessPhoenix in order to restart your application process.

Inversion

Answer 10

this worked for me:

Intent mStartActivity = new Intent(ctx.getApplicationContext(), ActivityMain.class);


    mStartActivity.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
    mStartActivity.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB)
        mStartActivity.addFlags(0x8000); // equal to Intent.FLAG_ACTIVITY_CLEAR_TASK

   int mPendingIntentId = 123456;


    PendingIntent mPendingIntent = PendingIntent.getActivity(ctx, mPendingIntentId, mStartActivity, PendingIntent.FLAG_CANCEL_CURRENT);
    AlarmManager mgr = (AlarmManager) ctx.getSystemService(Context.ALARM_SERVICE);
    mgr.set(AlarmManager.RTC, System.currentTimeMillis() + 1000, mPendingIntent);

    ActivityManager manager =  (ActivityManager) ctx.getApplicationContext().getSystemService(ctx.getApplicationContext().ACTIVITY_SERVICE);
    List<ActivityManager.RunningAppProcessInfo> activityes = ((ActivityManager)manager).getRunningAppProcesses();




    ((Activity)ctx).moveTaskToBack(true);
    manager.killBackgroundProcesses("com.yourpackagename");
    System.exit(0);

Heedful

Answer 11

You should checkout this question:

Restarting Android app programmatically

The way to do it is:

private void restartApp() 
{
   Intent intent = new Intent(getApplicationContext(), YourStarterActivity.class);
   int mPendingIntentId = MAGICAL_NUMBER;
   PendingIntent mPendingIntent = PendingIntent.getActivity(getApplicationContext(), mPendingIntentId, intent, PendingIntent.FLAG_CANCEL_CURRENT);
   AlarmManager mgr = (AlarmManager) getApplicationContext().getSystemService(Context.ALARM_SERVICE);
   mgr.set(AlarmManager.RTC, System.currentTimeMillis() + 100, mPendingIntent);
   System.exit(0);
}

Liberati

Answer 12

After hard thinking and testing I finally got the right way of calling my activity to recreate when the app is left with the home button :

android:clearTaskOnLaunch

in the manifest

@Override
public void onRestart(){
    onCreate();
}

That does the trick...(better than when it is put in onResume which is called each time you launch the app, even the first time, causing a double display)

Matronage

That sounds bad. You should only need the clearTaskOnLaunch attribute. How are you launching your app in the first place? Directly from Eclipse using the ADT tools? If so, there was a bug that meant apps weren't being launched properly from Eclipse. It's since been fixed. – Determined

yeah, directly from eclipse. but i tried with only clearTaskOnLaunch, and i coulnt get it to work... – Matronage

Hi how to add onRestart() method. Can you give a snippet?Thanks – Haematozoon

Folks, please do not call onCreate() from onRestart(). These (creation and restart) are two different events. If you want to have them execute the same code, please do: void myOnCreate() { ... } void onCreate(){myOnCreate();} void onRestart() {myOnCreate();} instead. – Merwin

@18446744073709551615: Can you explain why? – Ragsdale

@Ragsdale Because it makes your code unmaintainable. It is generally correct when function onRestart() calls super.onRestart(). But if you call onCreate() from onRestart(), this perfectly sane assumption becomes wrong for your project. For example, it is also generally correct, when you realize that you need some functionality in all activities, to define your class ActivityWithSomething and change extends Activity to extends ActivityWithSomething for all activities in the project. – Merwin

@Fraggles, continued: But if at some point onCreate() is called from from onRestart(), it may result in a crash that will be very difficult to debug, because when you debug code you assume that it is sane. Sane code should be reused, insane code should be rewritten from scratch. – Merwin