Killing one activity from another

Question

I have two activities A and B. B is a transparent pass through activity, and A is seen. I want to kill B by pressing a button A.

Here's what I've tried so far:

B obj=new B();
obj.finish();

I created an object of B and tried to kill it. That didn't work.

intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                intent.putExtra("keep", true);
                startActivity(intent);

What this code is supposed to do is clear the top most activity, which is B and call B again, except this time I'm passing a value such that B kills itself after a few seconds.

This only piled up more instances of the activity for some reason. Or at least I think that's what happened because the screen became pixelated due to many transparent activities.

Here's my manifest:

<activity
        android:name="com.xxx.xxx.B"
        android:excludeFromRecents="true"
        android:theme="@android:style/Theme.Translucent.NoTitleBar"
        android:clearTaskOnLaunch="true" >
    </activity>

What do I have to do so that, when I hit a button once the activity is displayed and the second time kills it? The creation part is obviously taken care of. My activity B pops up, I want to kill it now that B is on top.

EDIT

I tried this with a checkBox, here's the code:

enable.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View arg0) {
            // TODO Auto-generated method stub
            finishActivity(0);
            Intent intent = new Intent(A.this, B.class);
            if (enable.isChecked()) {
                intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                intent.putExtra("keep", true);
                intent.putExtra("value", 10);
                startActivityForResult(intent, 0);
            }
            else
            {
                intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                intent.putExtra("keep", false);
                startActivityForResult(intent, 0);
            }
        }
    });

When enable is checked the activity is called, which works fine. But they keep piling on. It's not like this A->B->A->B when I check and uncheck the checkBox. It's A->B->BB->BBB

Your question is not clear. A launches B which is transparent. And do you want to stop B by clicking a button from A when B is on top? — gezdy, Jan 16 '13 at 10:22
@gezdy No it isn't. I can use A as it is. I just need to find a way to close B. Please try it out before posting. — Karthik Balakrishnan, Jan 16 '13 at 10:27
possible duplicate of [Finish an activity from another activity](http://stackoverflow.com/questions/10379134/finish-an-activity-from-another-activity) — MKJParekh, Sep 25 '15 at 13:01

score 50 · Accepted Answer · edited Jan 07 '18 at 17:55

50

You could try to directly kill an activity by calling a static method in that activity:

Activity A should have a variable

 static ActivityA activityA;

In onCreate state:

 activityA = this;

and add this method:

public static ActivityA getInstance(){
   return   activityA;
 }

In activity B, call the function getInstance()

ActivityA.getInstance().finish();

edited Jan 07 '18 at 17:55

YakovL

7,557
12
62
102

answered Jan 16 '13 at 10:58

Lumis

21,517
8
63
67

I want it to kill the app only if the checkBox is disabled. Isn't there a way to just pass a variable without using intents? – Karthik Balakrishnan Jan 16 '13 at 11:02
Yes, use the above getInstance, then you can access any public variable and method in the activityA. In activity B, state ActivityA activityA = ActivityA.getInstance(); Then simply check your box by if(activityA.checkBox){....} – Lumis Jan 16 '13 at 11:08
2

When you close ActivtyA, kill the reference to it in Activity B: activityA = null; – Lumis Jan 16 '13 at 11:11
I understand why the null pointer exception arises. The activity hadn't been called yet. – Karthik Balakrishnan Jan 16 '13 at 11:21
1

I don't think so, but it is a way to access public items of another class, which includes Activity, which still only a class. Another way to share varibales is to create a static varibales in a separate class, then all activities can use it. – Lumis Jan 16 '13 at 11:26
Yes, you can check if the instance is null first – Lumis Jan 16 '13 at 11:28
This is just a singleton approach...Not helpful – DJphy May 19 '15 at 06:18
Nice, Really simple . TX – ClaudioC Oct 06 '17 at 15:33
You should strictly avoid declaring android context objects (such as activity) as static because memory leaks could occur. – user221256 Jan 07 '18 at 18:34
make static ActivityA activityA -> public static ActivityA activityA – aac Apr 17 '19 at 06:05

score 0 · Answer 2 · answered May 08 '13 at 10:43

0

I found a nice way to finish one activity from another, it is similar to what Lumis did. So if you want to close ActivityA from ActivityB you can do this:

In ActivityA do:

className = this.getClass().getName();

and pass it on to AvtivityB. Then in ActivityB do:

((Activity) Class.forName(className).newInstance()).finish();

You can put a string with the name of your class into className yourself, but it needs to be a full name with package too.

answered May 08 '13 at 10:43

a b

1
1

4

It doesn't seem to work and I fail to understand how this could work. The code basically creates a new activity object and then calls finish on it. However, this object is not the activity object stored in the stack. Thus, the activity in the stack stays there. – omega Sep 06 '13 at 15:27

score 0 · Answer 3 · answered Feb 08 '21 at 18:08

in my opinion, the clearer approach is create a local broadcast, in this way no memory leak or null problem. Actually this is the exact and proficient way for passing data to previous activity. First, create a reciever in Activity_A and register it on resume and uregister it on destroy. In Activi_A (in my case Bg_show Class) :

 BroadcastReceiver bgshowBroacast = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String extra = intent.getStringExtra("BROADCAST");
            if (extra != null) {
                if (extra.equalsIgnoreCase("finishBgShowActivity")) {

                    finish();
                    Log.i(TAG, "onReceive: Bg_show_BroadCast receive from bg_send class ");
                }
            }
        }
    };

    @Override
    protected void onResume() {
        super.onResume();
        LocalBroadcastManager.getInstance(mContext).registerReceiver(bgshowBroacast, new IntentFilter("BG_SHOW_BROADCAST"));
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        LocalBroadcastManager.getInstance(mContext).unregisterReceiver(bgshowBroacast);
    }

Then in Activity_B (in my case Bg_send Class) :

Intent intent = new Intent("BG_SHOW_BROADCAST");
                        intent.putExtra("BROADCAST", "finishBgShowActivity");
                        LocalBroadcastManager.getInstance(mContext)
                                .sendBroadcast(intent);

Thus the previous activity will finish where the receiver registered.

Happy coding.... .

score -1 · Answer 4 · answered Jul 19 '17 at 21:06

-1

Create static Class variable to save the instance: static SampleActivity sampleActivity;

On Create of first Activity save the Instance, like this: incidenteActivity = this;

Create a static method to get the instance:

public static SampleActivity getInstance(){
    return   sampleActivity;
}

wherever you want call:

SampleActivity.getInstance().finish();

it really works, regards,

answered Jul 19 '17 at 21:06

Joilson Cardoso

93
1
3

Thank you @Joilson. But, what's the difference between already accepted answer (by @Lumis) and your answer. – Rohit Sharma Mar 01 '18 at 12:34

Killing one activity from another

4 Answers4

Linked