Dialogs / AlertDialogs: How to "block execution" while dialog is up (.NET-style)

Question

Hey!

Coming from the .NET-environment Im am now looking to understand how Dialogs work in Android.

In .NET, when calling MessageBox.Show(...) that creates and shows a popup dialog. In the call to Show I can specify what buttons should be available in the popup, for example:

DialogResult myDialogResult = MessageBox.Show("My text here", "My caption here", MessageBoxButtons.YesNoCancel);

As you can see, the call to Show returns a DialogResult when a button is pressed in the popup, informing me what button was clicked. Note that in .NET, execution is halted at the line where the call to Show(...) is made, so it can return the value when a button is pressed.

If I in the above example press "No" the myDialogResult will be equal to

myDialogResult == DialogResult.No

Since I find the .NET-way of using/creating popups very easy and intuitive, I would like that way of creating popups in Android too.

So, the question is if anyone know how to "halt execution" like with the MessageBox.Show, and then return a value whenever the Button is pressed (and the dialog goes away)?

Regards

---

EDIT 1: To be a little bit more clear:

I need for the execution to halt and wait until the user has chosen a button to click in the popup. The code that follow the call to show the Dialog is dependent on what button is clicked in the Dialog.

Thats why I cannot use what Erich and Alex suggest, since writing code in the onClick-methods as suggested below is not gonna work. The reason is that I cannot continue the "normal execution". Let me take an example:

Let me take an example:

int nextStep = 0; // this variable will not be reached from within the onClick-methods

AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setMessage("Hello!")
       .setPositiveButton("Ok", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int id) {
                nextStep = 1; // *** COMPILER ERROR!! ***
            }
        })
        .setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int id) {
                nextStep = 2; // *** COMPILER ERROR!! ***
            }
        })
        .create().show();

if (nextStep == 1)
{
    // then do some damage
}
else if (nextStep == 2
    // dont do damage

If I wanted the execution to be dependent on the choice in the popup, I would somehow have to make all the variables in the "normal execution" (in this case nextStep) available in the onClick-methods, and that sounds like hell to me.

EDIT 2:

Another obvious example would be a popup asking "Do you want to continue" with the options "Yes" and "No".

If the user presses "Yes", the whole method should be aborted otherwise it should continue execution. How do you solve that nicely?

Regards

Answer 1

you set onclick listeners to you buttons. dissmis dialog and do your action. Don't need to halt anything

protected Dialog onCreateDialog(int id) {
  return new AlertDialog.Builder(this).setTitle(R.string.no_connection).setIcon(android.R.drawable.ic_dialog_alert).setView(textEntryView).setPositiveButton(R.string.exit, new DialogInterface.OnClickListener() 
{

   public void onClick(DialogInterface dialog, int whichButton) {

  // Here goes what you want to do
  }

})
}

to call - ex - showDialog(DIALOG_ERROR_PREF);

More http://developer.android.com/guide/topics/ui/dialogs.html

Answer 2

In Android, the syntax is different from .NET:

AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setMessage("Hello!")
       .setPositiveButton("Ok", new DialogInterface.OnClickListener() {
           public void onClick(DialogInterface dialog, int id) {
               // Handle Ok
           }
       })
       .setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
           public void onClick(DialogInterface dialog, int id) {
               // Handle Cancel
           }
       })
       .create();

Will get you a dialog with two buttons and you handle the button clicks with callbacks. You might be able to write some code to make the syntax more closely resemble .NET, but the dialog lifecycle is pretty intertwined with Activity, so in the end, it might be more trouble than it's worth. Additional dialog references are here.

Answer 3

This is the simplest way:

new AlertDialog.Builder(this).setTitle("title").setMessage("message").create().show();

Answer 4

In an attempt to optimize memory and performance dialogs in Android are asynchronous (they are also managed for this reason). Comming from the Windows world, you are used to modal dialogs. Android dialogs are modal but more like non-modal when it comes to execution. Execution does not stop after displaying a dialog.

The best description of Dialogs in Android I have seen is in "Pro Android" http://www.apress.com/book/view/1430215968

This is not a perfect explanation but it should help you to wrap your brain around the differences between Dialogs in Windows and Android. In Windows you want to do A, ask a question with a dialog, and then do B or C. In android design A with all the code you need for B and C in the onClick() of the OnClickListener(s) for the dialog. Then do A and launch the dialog. You’re done with A! When the user clicks a button B or C will get executed.

Windows
-------
A code
launch dialog
user picks B or C
B or C code
done!

Android
-------
OnClick for B code (does not get executed yet)
OnClick for C code (does not get executed yet)
A code
launch dialog
done!
user picks B or C

Answer 5

Ted, you don't want to do this, really :) The biggest reason is that if you block the UI thread while you are displaying a Dialog, you will block the thread that's in charge of drawing and handling the events of your Dialog. Which means your dialog will be unresponsive. You will also cause ANRs if the user takes more than a few seconds to click the dialog.

Erich's answer is exactly what you need. I know it's not what you want, but that doesn't matter. We've designed Android to prevent developers from writing synchronous dialogs so you don't really have much of a choice.

Answer 6

In Android Dialogs are asynchronous so you're going to have to structure your code a little differently.

So in C# your logic ran something like this in pseudocode:

void doSomeStuff() {
    int result = showDialog("Pick Yes or No");

    if (result == YES) {
        //do stuff for yes
    }
    else if (result == NO) {
        //do stuff for no
    }

    //finish off here
}

For Android it's going to have to be less neat. Think of it like so. You'll have an OnClickListener like this:

public void onClick(DialogInterface dialog, int whichButton) {
   if (whichButton == BUTTON_POSITIVE) {
      doOptionYes();
   }
   else if (whichButton == BUTTON_NEGATIVE) {
      doOptionNo();
   }
}

Which is then supported by the following methods:

void doOptionYes() {
    //do stuff for yes
    endThings();
}

void doOptionNo() {
    //do stuff for no
    endThings();
}

void endThings() {
    //clean up here
}

So what was one method is now four. It may not seem as neat but that's how it works I'm afraid.