How to kill an Android activity when leaving it so that it cannot be accessed from the back button?

In an given Android activity, I would like to start a new activity for the user at some point. Once they leave the first activity and arrive at the second, the first activity is stale and I want to remove it completely so it can not be accessed again from the back button.

How is the best way to accomplish this? How do I kill or destroy this activity immediately after the user has launched the new activity?

You just need to call finish()

Intent intent = new Intent(this, NextActivity.class);
startActivity(intent);
finish();

Setting android:noHistory="true" on the activity in your manifest will remove an activity from the stack whenever it is navigated away from. see here

you can use:

intent.setFlags(Intent.FLAG_ACTIVITY_NO_HISTORY);

You can also add android:noHistory="true" to your Activity tag in AndroidManifest.xml.

<activity
            ...
            android:noHistory="true">
</activity>

Yes, all you need to do is call finish() in any Activity you would like to close.

Write this in each "new activity" after you initialized your new intent->

Intent i = new Intent(this, yourClass.class);
startActivity(i);
finish();

Finally, I got a solution!

My Context is:- I want disconnect socket connection when activity destroyed, I tried to finish() activity but it didn't work me, its keep connection live somewhere.

so I use android.os.Process.killProcess(android.os.Process.myPid()); its kill my activity and i used android:excludeFromRecents="true" for remove from recent activity .

Add this attribute to you activity in manifest file. android:noHistory="true"

In Kotlin, you may use this

startActivity(Intent(context, newActivity::class.java))
finish()

Or you can use this also

val intent = Intent(context, newActivity::class.java))
startActivity(intent)
finish()

You've below options to remove an activity from the back stack for a particular task.

1. Call finish() method just after startActivity() like this:

        startActivity(new Intent(FirstActivity.this, SecondActivity.class));
        finish();
   

2. Add an Intent flag like so:

        startActivity(new Intent(FirstActivity.this, SecondActivity.class).addFlags(Intent.FLAG_ACTIVITY_NO_HISTORY));
   

3. Add noHistory=true in your manifest file for that particular activity

You just need to use below code when launching the new activity.

startActivity(new Intent(this, newactivity.class));
finish();