How to prevent going back to the previous activity?

My suggestion would be to finish the activity that you don't want the users to go back to. For instance, in your sign in activity, right after you call startActivity, call finish(). When the users hit the back button, they will not be able to go to the sign in activity because it has been killed off the stack.

Following solution can be pretty useful in the usual login / main activity scenario or implementing a blocking screen.

To minimize the app rather than going back to previous activity, you can override onBackPressed() like this:

@Overridepublic void onBackPressed() {    moveTaskToBack(true);}

moveTaskToBack(boolean nonRoot) leaves your back stack as it is, just puts your task (all activities) in background. Same as if user pressed Home button.

Parameter boolean nonRoot - If false then this only works if the activity is the root of a task; if true it will work for any activity in a task.

I'm not sure exactly what you want, but it sounds like it should be possible, and it also sounds like you're already on the right track.

Here are a few links that might help:

Disable back button in android

  MyActivity.java =>    @Override    public void onBackPressed() {       return;    }

How can I disable 'go back' to some activity?

  AndroidManifest.xml =><activity android:name=".SplashActivity" android:noHistory="true"/>