Trying to Implement an Exit Confirmation in my Android app

I've already discovered that you can't override the Home button on an Android phone. It exits the application, it 开发者_如何学编程ALWAYS exits the application, and it DOESN'T bother with any sort of namby-pamby confirmation. I suppose I understand Google's reasoning -- but I do think it's a bit short-sighted...

Anyway, (before I learned about the Home button), I set up my app so the user can exit the application through the Options Menu -- using onCreateOptionsMenu() and an XML file, I set up a simple pop-up menu that's displayed when the Menu button is pressed. One of its choices is Exit, and it works fine.

However, it occurred to me that it might be good practice to add a confirmation dialog to the exit process (even if it could also be considered superfluous). So, I created an AlertDialog with the title "Do you want to Exit?" and Yes and No buttons...

The click listeners for the buttons are simple and just set exitConfirm (a boolean) true or false. The code that handles the Exit menu choice then cleans up after my application and executes finish() or not depending on the state of exitConfirm...

Unfortunately, it completely doesn't work... All of the code in onOptionsItemSelected() for the exit case executes and THEN the Dialog is displayed!! I suppose I should've seen that coming. And I suppose if I keep pounding on it, I'll come up with a way accomplish this, but I thought I would ask the community for suggestions - so, does anybody have a suggestion for a way to smoothly exit an Android application in a manner that includes the step of getting confirmation from the user??

Thanks, R.

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First of all - this is a terrible practice. Asking for confirmation may be a nice option on a desktop application, but you're writing a mobile application. It's different. Actually, I need to write that in bold:

You are not writing a desktop application.

I recommend: No splash screen. No exit option. Definitely no exit confirmation. Here is an excellent question about it.

For your question: Use setPositiveButton and setNegativeButton to handle buttons.

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Short answer:

You should read: When to Include an Exit Button in Android Apps.

Long answer: You can try something like this:

protected Dialog onCreateDialog(int id) {
        Dialog dialog = null;

        switch (id) {
        case MENU_QUIT:
            AlertDialog.Builder builder = new AlertDialog.Builder(this);
            builder.setMessage(getString(R.string.main_screen_quit_text))
                    .setCancelable(false)
                    .setPositiveButton(
                            getString(R.string.main_screen_quit_yes),
                            new DialogInterface.OnClickListener() {
                                public void onClick(DialogInterface dialog,
                                        int id) {

                                    moveTaskToBack(true);
                                }
                            })
                    .setNegativeButton(getString(R.string.main_screen_quit_no),
                            new DialogInterface.OnClickListener() {
                                public void onClick(DialogInterface dialog,
                                        int id) {
                                    dialog.cancel();
                                }
                            });
            AlertDialog alert = builder.create();
            return alert;
        default:
            dialog = null;
        }
        return dialog;
    }

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Apparently, it's generally considered not to be cool to have an exit button (or menu item, or whatever) in your Android app. Apparently, this is because your application doesn't really exit. It's only minimized out of the way, and presumably, the OS will take care of it eventually.

However, if what you're doing requires some level of clean-up when you're done doing it, this is what I think I know about that:

1. Pay careful attention to the various Android "Life Cycle Methods", especially what kicks them off. Life cycle methods include onCreate(), onStart(), onResume(), onPause(), and onStop(). There's also onDestroy() -- the complement to onCreate() -- but I don't currently use it.

2. These methods are called in response to various events (like pressing the Home button), but what was important in my case was that minimizing the application calls onPause() and maximizing it calls onResume(). Hence, I needed to call my set up and tear down methods from those locations, and NOT, for instance, from onCreate() and onDestroy().

3. There is a function called finish() that I used to use all over my code. Now it's only in the method that's called to handle loss of communication with my external device. I believe the results of calling finish() are exactly the results of pressing the Home button -- so, it's just a way to "press" the Home button in software.

The long-winded conclusion to all this is the Home button absolutely WILL hide your application from the user's view. You cannot trap this key press -- no matter how badly you want to add some sort of, "Are you sure??" functionality. However, the app's been minimized, not closed, and this can either be good or bad. If you've written your start up and shut down code properly (and added it to the proper life cycle methods), you won't blow things up, and your user will be able to easily return to your app once they've learned to long press the Home button to see a list of minimized apps.

With any luck, I suppose, they'll blame their frustration on Google, and not on you...