Is there any event to catch when pop() a screen after back button pressed?

Question

When a button is pressed on Screen A, I push Screen B. And when Back button is pressed on Screen B, I want Screen A to understand that to update Screen. Is there any way to handle this?

score 2 · Accepted Answer · edited Jan 09 '14 at 11:10

2

When Screen B is popped, it will have its onUiEngineAttached(boolean) function called, with the parameter set to false. If Screen B held a reference to Screen A, it could then trigger whatever updating is needed.

Another way is to setup your own Listener where Screen B would provide the event and Screen A would listen for the event. Again, you would probably fire the event from the onUiEngineAttached(boolean) function.

edited Jan 09 '14 at 11:10

BenMorel

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answered May 10 '11 at 12:42

Fostah

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Thank you, i will try onUiEngineAttached(boolean) method. – redline May 10 '11 at 13:37

score 2 · Answer 2 · edited May 23 '17 at 11:47

2

You could use a callback pattern. Check my another post for details. Upon any UI event on your Screen B (e.g. a button is pressed) the Screen B runs the callback passing any parameter if needed. Going this way your Screen A keeps its original/clean interface.

You can detect the device 'Back' btn press with this code:

protected boolean keyChar(char c, int status, int time) {
    if (c == Characters.ESCAPE) {
        // .. run callback here ..
        close(); // actually close the Screen B
        return true;
    }
    return super.keyChar(c, status, time);
}

edited May 23 '17 at 11:47

Community

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answered May 10 '11 at 13:02

Vit Khudenko

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I already use `keyChar()`. And I just passed the reference of Screen A to Screen B and called an update method of A. It works but I don't know if it is a good way to pass the reference. I don't really know what callbacks do. But I use a ListField and ListCallBack in Screen A. I realize that `drawListRow()` method of ListCallback is called when I press back button from Screen B. So I think a callback will be usefull here. I will look into it, thank you. – redline May 10 '11 at 13:34
Just to be clear: I am not talking about ListCallBack. This is totally another concept. Passing a reference works Ok, it just creates a too monolithic code, that will be harder to change later. – Vit Khudenko May 10 '11 at 13:44
Yes, i know it won't be a ListCallBack ofcourse. And I am aware of problems of passing parameter, I will change it. – redline May 10 '11 at 13:57

score 1 · Answer 3 · answered May 10 '11 at 17:43

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Screen B is popped off of the stack, so it will get the onUiEngineAttached() callback. But you are interested in screen A, which will get a different callback - Screen.onExposed().

answered May 10 '11 at 17:43

Michael Donohue

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Thank you, i will also try this function. – redline May 10 '11 at 22:49

score -1 · Answer 4 · answered May 10 '11 at 12:31

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I think this can be done using YUI History manager.

answered May 10 '11 at 12:31

Amareswar

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Is there any event to catch when pop() a screen after back button pressed?

4 Answers4