Question

I’m trying to create a modal confirmation dialog box. I’d like it to work like Window.confirm(""), where I can just call it, and get a boolean response.

My trouble is I’m not sure how to do it. I’m trying to use MVP in my application. Here is the code I have so far:

public class DialogBoxPresenter implements Presenter {

    public interface Display {

        Label getDialogText();

        Button getAffirmativeButton();

        Button getCancelButton();

        Widget asWidget();

        public void center();

        public void hide();

        public void setHeader(String text);
    }
    private Display display;
    private String header;
    private String dialogText;
    private String cancelButtonText;
    private String affirmativeButtonText;

    protected DialogBoxPresenter() {
    }

    public DialogBoxPresenter(Display display, String header, String dialogText, String cancelButtonText, String affirmativeButtonText) {
        this.display = display;
        this.header = header;
        this.dialogText = dialogText;
        this.cancelButtonText = cancelButtonText;
        this.affirmativeButtonText = affirmativeButtonText;

        bind();
    }

    public DialogBoxPresenter(Display display, String header, String dialogText) {
        this.display = display;
        this.header = header;
        this.dialogText = dialogText;
        this.cancelButtonText = "Cancel";
        this.affirmativeButtonText = "OK";

        bind();
    }

    private void bind() {

        this.display.getDialogText().setText(dialogText);
        this.display.getAffirmativeButton().setText(affirmativeButtonText);
        this.display.getCancelButton().setText(cancelButtonText);
        this.display.setHeader(header);

        addClickHandlers();

    }

    private void addClickHandlers() {
        this.display.getAffirmativeButton().addClickHandler(new ClickHandler() {

            @Override
            public void onClick(ClickEvent event) {
                doAffirmative();
            }
        });

        this.display.getCancelButton().addClickHandler(new ClickHandler() {

            @Override
            public void onClick(ClickEvent event) {
                doCancel();
            }
        });
    }

    private void doAffirmative() {
        //do something
        display.hide();
    }

    private void doCancel() {
        //do something
        display.hide();
    }

    public void init() {
        display.center();
    }

    @Override
    public void go(HasWidgets container) {
        container.clear();
        container.add(display.asWidget());
    }
}

and my view:

public class DialogBoxView extends DialogBox implements DialogBoxPresenter.Display {

    private Label dialogText;
    private Button affirmativeButton;
    private Button cancelButton;
    private VerticalPanel container;

    public DialogBoxView() {
        //init items
        dialogText = new Label();

        affirmativeButton = new Button();
        cancelButton = new Button();

        container = new VerticalPanel();

        setGlassEnabled(true);
        setAnimationEnabled(true);
        setModal(false);

        init();
    }

    private void init() {
        //add items
        container.add(dialogText);

        HorizontalPanel hp = new HorizontalPanel();
        hp.add(affirmativeButton);
        hp.add(cancelButton);

        container.add(hp);
        this.add(container);
    }

    @Override
    public Widget asWidget() {
        return this;
    }

    @Override
    public Label getDialogText() {
       return dialogText;
    }

    @Override
    public Button getAffirmativeButton() {
        return affirmativeButton;
    }

    @Override
    public Button getCancelButton() {
       return cancelButton;
    }

    @Override
    public void setHeader(String text) {
       this.setText(text);
    }

}

Answer 1

You’re not going to be able to have it work in exactly the same way as Window.confirm(). The problem is that all of the javascript in a web page runs in a single thread. You’ll notice that as long as a standard confirm dialog is open, the rest of the page goes dead. That’s because the one javascript thread is blocked, waiting for confirm() to return. If you were to create a similar method for your dialog, as long as it was waiting for that method to return no user generated events would be processed and so your dialog wouldn’t work. I hope that makes sense.

The best you will be able to do is similar to what the GWT library does for RPC calls — the AsyncCallback interface. You could even reuse that interface yourself, or you might prefer to roll your own:

public interface DialogCallback {
    void onOk();
    void onCancel();
}

Instead of Window.confirm(String), your method signature will be more like Dialog.confirm(String,DialogCallback). Then your dialog just keeps a reference to the callback that’s passed in, and where you have // do something in your code you make calls to onOk and onCancel.