Issue in PopUpScreen

问题

OnClick of an image I am popping up a screen which has dropdown code, where I have to select the data and pass it to the screen from where it was popped up, after selecting the data from the dropdown the popupscreen should disappear passing the selected ocf value to the firstscreen. I am not able to hide the popupscreen after selection and am not able to pass the data back to the first screen

This code will call a popup screen

if (field==bitmapField1) {
     UiApplication.getUiApplication().pushScreen(new MyPopup());
}

This is the popped up screen

public class MyPopup extends PopupScreen {
      ObjectChoiceField ocf;

        public MyPopup() {
             super(new VerticalFieldManager(), Field.FOCUSABLE);
            // this listener 'listens' for any event (see at the bottom)
           FieldListener listener = new FieldListener();

         TimeZone[] zone = TimeZoneUtilities.getAvailableTimeZones();
           ocf = new ObjectChoiceField("Set Timezone", zone);
             ocf.setChangeListener(listener);
             add(ocf);
       }

     class FieldListener implements FieldChangeListener {
           public void fieldChanged(Field f, int context) {
                  if (f == ocf) {
                       Object ob = ocf.getChoice(ocf.getSelectedIndex());
                       String str = ob.toString();
                       Dialog.alert(str);
                  }
           }
     }
}

回答1:

You should add an attribute to your PopUpScreen that references the Screen that launched the PopUp. That way, you can send parameters to the parent Screen without problems:

public class MyPopup extends PopupScreen {
    ObjectChoiceField ocf;
    MainScreen parentScreen;

    public MyPopup(MainScreen parentScreen) {
            this.parentScreen = parentScreen;
            ...

And when you launch the PopUp:

if(field==bitmapField1){
    UiApplication.getUiApplication().pushScreen(new MyPopup(this));
}

回答2:

Here is my CustomChoiceField. Hope it helps:

public class ChoiceField extends HorizontalFieldManager{
    protected boolean isEnabled = true;
    protected String label;
    protected Object[] choices;
    protected int selectedIndex = -1;
    protected ButtonField chooseField;
    protected Font textFont = ClientConstants.Fonts.NORMAL;
    protected PopUpList popup;
    private FieldChangeListener fieldChangeListener;

    public ChoiceField(final String label,Object[] choices){
        this.label = label;
        if (choices == null || choices.length == 0){
            this.choices = new String []{};
            setEnabled(false);
        }else {
            this.choices = choices;
        }
        chooseField = new ButtonField("Please Choose");
        chooseField.setChangeListener(new FieldChangeListener() {
            public void fieldChanged(Field field, int context) {
                UiApplication.getUiApplication().invokeAndWait(new Runnable() {
                    public void run() {
                        if (isEnabled){
                            UiApplication.getUiApplication().pushScreen(popup);
                        }
                    }
                });
            }
        });
        chooseField.setPadding(0, 0, 0, Display.getWidth() - 20 - chooseField.getPreferredWidth());
        popup = new PopUpList(this.choices);
        add (chooseField);
    }
    public void setChoices(Object[] choices) {
        if (choices == null || choices.length == 0){
            this.choices = new String []{};
            chooseField.setLabel("");
        }else {
            this.choices = choices;
            chooseField.setLabel(this.choices[0].toString());
        }
        popup = new PopUpList(this.choices);
    }
    public void setChangeListener(FieldChangeListener fieldChangeListener){
        this.fieldChangeListener = fieldChangeListener;
    }
    public void setEnabled (boolean isEnabled){
        this.isEnabled = isEnabled;
    }
    public Object getSelectedItem () throws ChoiceFieldNotSelectedException{
        if (selectedIndex == -1){
            throw new ChoiceFieldNotSelectedException(label);
        }
        return choices[selectedIndex];
    }
    public void setSelectedObject(Object selectedObject){
        for(int i=0;i<choices.length;i++)
            if(choices[i].equals(selectedObject)){
                selectedIndex = i;
                break;
            }
        chooseField.setLabel(choices[selectedIndex].toString());
        ChoiceField.this.invalidate();
    }
    protected void paint(Graphics graphics) {
        if (label.length()>0){
            graphics.setColor(Color.WHITE);
            Font f = textFont;
            while (f.getAdvance(label + ": ") > Display.getWidth() - 30 - chooseField.getPreferredWidth()){
                if (f.getHeight() == 8){
                    break;
                }
                f = f.derive(f.getStyle(),f.getHeight()-1);
            }
            graphics.setFont(f);
            graphics.drawText(label + ": ", 10, (chooseField.getHeight() - textFont.getHeight()) / 2);
        }
        super.paint(graphics);
    }
    class PopUpList extends PopupScreen{
        private ObjectListField listField = null;
        public PopUpList(final Object [] choices) {
            super(new VerticalFieldManager(Manager.VERTICAL_SCROLL | Manager.VERTICAL_SCROLLBAR));
            listField = new ObjectListField(choices.length){
                protected void layout(int width, int height) {
                    super.layout(Math.min(width, getPreferredWidth()), height);
                }
                public int getPreferredWidth(ListField list) {
                    int width = 0;
                    for (int i=0;i<choices.length;i++){
                        if (width < textFont.getAdvance(choices[i].toString())){
                            width = textFont.getAdvance(choices[i].toString());
                        }
                    }
                    return width;
                }
            };
            listField.setFont(textFont);
            for (int i=0;i<choices.length;i++){
                listField.insert(i, choices[i]);
            }
            add(listField);
        }
        protected boolean navigationClick(int status, int time) {
            clicked();
            closed();
            return super.navigationClick(status, time);
        }
        protected boolean keyChar(char c, int status, int time) {
            if (c == Characters.ENTER){
                clicked();
                closed();
            }else if (c == Characters.ESCAPE){
                closed();
            }
            return super.keyChar(c, status, time);
        }
        protected void clicked(){
            try{
                selectedIndex = listField.getSelectedIndex();
                chooseField.setLabel(choices[selectedIndex].toString());
                ChoiceField.this.invalidate();
                if (fieldChangeListener != null){
                    fieldChangeListener.fieldChanged(ChoiceField.this, selectedIndex);
                }
            }catch (ArrayIndexOutOfBoundsException e) {
            }
        }
        protected void closed(){
            UiApplication.getUiApplication().invokeAndWait(new Runnable() {
                public void run() {
                    try {
                        UiApplication.getUiApplication().popScreen(PopUpList.this);
                    }catch(Exception e){
                    }
                }
            });
        }
    }
}

回答3:

On your PopUp screen ObjectChoiceField.... fieldChange() method..... call onClose() method.

protected boolean onClose(){
uiapplication.getUiapplication.popScreen(this);
return true;
}

回答4:

You can use a callback pattern to solve the problem you are facing . Check Blackberry: select item in a list, return to previous screen

回答5:

Open Dialog in synchronized EventLock . You will get your solution...

synchronized (UiApplication.getUiApplication().getEventLock()) {
    //Open your dialog here......       
    UiApplication.getUiApplication().pushScreen(new MyPopup());
}

来源：https://stackoverflow.com/questions/9772934/issue-in-popupscreen