how to do instant update in BB RIM? - blackberry

Question

I want to manually display a field.
public class Main_NewsDetail extends MainScreen {
private Custom_FontField slider;
private boolean a;
public Main_NewsDetail() {
super(USE_ALL_WIDTH);
slider = new Custom_FontField(
Bitmap.getBitmapResource("slider_thumb_normal.png"),
Bitmap.getBitmapResource("slider_progress_normal.png"),
Bitmap.getBitmapResource("slider_base_normal.png"),
Bitmap.getBitmapResource("slider_thumb_focused.png"),
Bitmap.getBitmapResource("slider_progress_focused.png"),
Bitmap.getBitmapResource("slider_base_focused.png"),
Bitmap.getBitmapResource("slider_thumb_pressed.png"),
Bitmap.getBitmapResource("slider_progress_pressed.png"),
Bitmap.getBitmapResource("slider_base_pressed.png"), 35, 10, 5,
5, FOCUSABLE);
if(a)
add(slider);
}
public class Custom_NewsDetailBottom extends Manager implements
FieldChangeListener {
Custom_NewsDetailBottom() {
super(Manager.USE_ALL_WIDTH | Manager.NO_VERTICAL_SCROLL
| Manager.NO_HORIZONTAL_SCROLL);
Background background = BackgroundFactory
.createBitmapBackground(bg);
setBackground(background);
fontbtn = new Custom_ButtonField(font, fontactive, fontactive) {
protected boolean navigationClick(int status, int time) {
a = !a; <-- here is to control field display
return true;
}
};
fontbtn.setChangeListener(this);
add(fontbtn);
}
protected void sublayout(int width, int height) {
Field field = getField(0);
layoutChild(field, font.getWidth(), font.getHeight());
setPositionChild(field, getGap(), 5);
width = Math.min(width, getPreferredWidth());
height = Math.min(height, getPreferredHeight());
setExtent(width, height);
}
public int getPreferredHeight() {
return 70;
}
public int getPreferredWidth() {
return Display.getWidth();
}
protected void paint(Graphics graphics) {
int rectHeight = getPreferredHeight();
int rectWidth = getPreferredWidth();
graphics.drawRect(0, 0, rectWidth, rectHeight);
super.paint(graphics);
}
private int getGap() {
return ((getPreferredWidth() / 4) - font.getWidth()) / 2;
}
public void fieldChanged(Field field, int context) {
if (field == sharebtn) {
} else if (field == commentbtn) {
Main.getUiApplication().pushScreen(new Main_Comments());
} else if (field == otherbtn) {
Main.getUiApplication().pushScreen(new Menu_Others());
}
}
public boolean keyDown(int keycode, int status) {
if (Keypad.key(keycode) == Keypad.KEY_ESCAPE) {
delete(slider);
return true;
}
return super.keyDown(keycode, status);
}
}
}
Above is the code that display a screen. In fontbtn, When click will change the variable true / false. However, it cannot update instant to display the field slider.
slider is something like seekbar in Android. In android, when click then can setvisibility but not blackberry RIM, so how to control it?

Answer 1

First of all, I would recommend not using variables with names like this if you can avoid it:
private boolean a;
Try to give it a name that's more descriptive, as that will help us understand your code better.
Next, it looks like you are testing the variable a before it ever has a chance to change, in the Main_NewsDetail constructor. So that won't work. Maybe try this in the Main_NewsDetail class:
/** separate boolean used because Field.isVisible() doesn't seem totally robust */
private boolean isSliderVisible = false;
private void setSliderVisible(boolean isVisible) {
if (isVisible != isSliderVisible) {
if (isVisible) {
add(slider);
} else {
delete(slider);
// but, we still retain the "slider" member variable, so it can be
// added again later
}
isSliderVisible = isVisible;
// I'm not actually sure that this is needed. I include it because I can't run this code right now!
invalidate();
}
}
Then, in your button click handler:
fontbtn = new Custom_ButtonField(font, fontactive, fontactive) {
protected boolean navigationClick(int status, int time) {
setSliderVisible(!isSliderVisible);
return true;
}
};
Now, this code can work because your Main_NewsDetail has only one Field in it, the slider. If there are actually multiple Field objects (which you probably will have), then you may need more complicated logic. You may want to show the slider in the same location every time. For that, you can record the index of the slider, in the list of all the Main_NewsDetails fields (for example, is the slider the 1st field, the 2nd, the 5th?). Then, instead of calling add(slider), you would do:
private void setSliderVisible(boolean isVisible) {
if (isVisible != isSliderVisible) {
if (isVisible) {
insert(slider, sliderIndex);
You might need to make Main_NewsDetail a subclass of Manager and implement the sublayout() method. That way, you can make sure that if isSliderVisible, you always lay out the slider in the same position.

Answer 2

Try calling Manager's invalidate-method to force a repaint for the managed area:
Marks this entire manager as requiring repainting.
Invoke this method to signal that this manager's entire region requires repainting.