Android: Prompt user to save changes when Back button is pressed

Question

I have an activity that contains several user editable items (an EditText field, RatingBar, etc). I\'d like to prompt the user if the back/home button is pressed and change

Answer 1

Here is some sample code:

@Override
public void onBackPressed() {       
    if (isDirty) {          
        new AlertDialog.Builder(this)
            .setTitle("You have made some changes.")
            .setMessage("Would you like to save before exiting?")
            //.setNegativeButton(android.R.string.no, null)            
            .setNegativeButton("No", new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface arg0, int arg1) {
                    MyActivity.super.onBackPressed();
                }
            })            
            .setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface arg0, int arg1) {                    
                    if (Save())
                        MyActivity.super.onBackPressed();
                }
            }).create().show();
    }
    else {
        MyActivity.super.onBackPressed();
    }
}

Answer 2

What do you think about this approach ..

private  void exit(){
    this.finish();
}

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
    if (keyCode == KeyEvent.KEYCODE_BACK && event.getRepeatCount() == 0) {

        AlertDialog.Builder alertbox = new AlertDialog.Builder(this);
        alertbox.setTitle("Message");
        alertbox.setMessage("Quit ??? ");

        alertbox.setPositiveButton("Yes",
                new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface arg0, int arg1) {
                        exit();
                    }
                });

        alertbox.setNeutralButton("No",
                new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface arg0, int arg1) {
                    }
                });

        alertbox.show();

        return true;
    } else {
        return super.onKeyDown(keyCode, event);
    }

}

Answer 3

I am doing the same thing that you do. I have one activity with a customer information (EditText for name, last name, email, ..., you know, EditText everywhere) and I used AsyncTask for that, and it works wonderfully.

    @Override
public void onBackPressed() 
{
            // start async task for save changes.
    new GuardandoContactoHilo().execute()
}

public void VolverAtras()
{
    super.onBackPressed();
}

public class GuardandoContactoHilo extends AsyncTask< Void, Void, Void> 
{

     private ProgressDialog saving;


    @Override
    protected void onPreExecute()
    {
        super.onPreExecute();
        saving = new ProgressDialog(cont);

        saving.setProgressStyle(ProgressDialog.STYLE_SPINNER);
        saving.setMessage("Saving customer ...");
        saving.show();
    }

    @Override
    protected void onPostExecute(Void result) 
    {
        super.onPostExecute(result);
        saving.dismiss();
        VolverAtras(); // go back !!
    }

    @Override
    synchronized protected Void doInBackground(Void... arg0) 
    {

        // do what you want to do before come back ! for example, save data ;)
        return null;
    }

}

Answer 4

You're not quite on the right track; what you should be doing is overriding onKeyDown() and listening for the back key, then overriding the default behavior:

@Override
public boolean onKeyDown(int keyCode, KeyEvent event)  {
    if (keyCode == KeyEvent.KEYCODE_BACK && event.getRepeatCount() == 0) {
        // do something on back.
        return true;
    }

    return super.onKeyDown(keyCode, event);
}

If you're only supporting Android 2.0 and higher, they've added an onBackPressed() you can use instead:

@Override
public void onBackPressed() {
    // do something on back.
    return;
}

This answer is essentially ripped from this blog post. Read it if you need long presses, compatibility support, support for virtual hard keys, or raw solutions like onPreIme() etc.