Создать идентификатор для вашего макета в Activity_main
CoordinatorLayout coordinatorLayout;
@Override
public void onBackPressed() {
coordinatorLayout= (CoordinatorLayout) findViewById(R.id.coordinatorLayout);
if (!doubleBackToExitPressedOnce) {
this.doubleBackToExitPressedOnce = true;
Snackbar.make(coordinatorLayout, "Do you really want to exit?", Snackbar.LENGTH_LONG)
.setAction("YES", new View.OnClickListener() {
@Override
public void onClick(View view) {
//button action here
System.exit(0);
}
}).setActionTextColor(Color.YELLOW)
.show();
new Handler().postDelayed(new Runnable() {
@Override
public void run() {
doubleBackToExitPressedOnce = false;
}
}, 2000);
}
Надеюсь, это поможет