问题
I am trying to push a new screen when a bitmap is "clicked" on the screen. For this I have created a Class from this post: Blackberry Clickable BitmapField whose partial code I've posted below:
public class CustomMenuButtonField extends Field{
Bitmap normal,focused;
...
protected boolean navigationClick(int status, int time)
{
// push new screen
fieldChangeNotify(0);
return true;
}
...
I want to push a new screen when the user clicks the bitmap. I have consulted this thread: Communicating between classes, but I still can't figure out the commands to call the new screen command. The UserInterface I have so far is:
public class UserInterface extends UiApplication {
public static void main(String[] args){
UserInterface theApp = new UserInterface();
theApp.enterEventDispatcher();
}
public UserInterface() {
pushScreen(new UserInterfaceScreen());
}
}
final class UserInterfaceScreen extends MainScreen {
public UserInterfaceScreen() {
...
What would be the command to pop up the new screen, and more importantly where would I be able to work on it? I know it should probably use pushScreen() but that is not recognized in that class. Would I create a new final class NewScreenFromClick extends MainScreen? and if so how would I call it and put it in the eventDispatcher. I've been going through the blackberry site but they don't have much sample code on this issue and I am very new to Java so this is fairly confusing to me.
回答1:
imageField imageField = new imageField ("",Field.FOCUSABLE,"image.png","image.png", 0x102839);
add(imageField );
FieldChangeListener listener = new FieldChangeListener() {
public void fieldChanged(Field field, int context) {
if (field == imageField ) {
home home = new home();//your screen
UiApplication.getUiApplication().pushScreen(home);
}
}
};
imageField .setChangeListener(listener);
//imagefield class is given below
package com.pl.button;
import net.rim.device.api.ui.*;
import net.rim.device.api.system.*;
public class imagefield extends Field {
private String _label;
private int _labelHeight;
private int _labelWidth;
private Font _font;
private Bitmap _currentPicture;
private Bitmap _onPicture;
private Bitmap _offPicture;
int color;
public imagefield (String text, long style ,String img, String img_hvr, int color){
super(style);
_offPicture = Bitmap.getBitmapResource(img);
_onPicture = Bitmap.getBitmapResource(img_hvr);
_font = getFont();
_label = text;
_labelHeight = _onPicture.getHeight();
_labelWidth = _onPicture.getWidth();
this.color = color;
_currentPicture = _offPicture;
}
/**
* @return The text on the button
*/
String getText(){
return _label;
}
/**
* Field implementation.
* @see net.rim.device.api.ui.Field#getPreferredHeight()
*/
public int getPreferredHeight(){
return _labelHeight;
}
/**
* Field implementation.
* @see net.rim.device.api.ui.Field#getPreferredWidth()
*/
public int getPreferredWidth(){
return _labelWidth;
}
/**
* Field implementation. Changes the picture when focus is gained.
* @see net.rim.device.api.ui.Field#onFocus(int)
*/
protected void onFocus(int direction) {
_currentPicture = _onPicture;
invalidate();
}
/**
* Field implementation. Changes picture back when focus is lost.
* @see net.rim.device.api.ui.Field#onUnfocus()
*/
protected void onUnfocus() {
_currentPicture = _offPicture;
invalidate();
}
/**
* Field implementation.
* @see net.rim.device.api.ui.Field#drawFocus(Graphics, boolean)
*/
protected void drawFocus(Graphics graphics, boolean on) {
// Do nothing
}
/**
* Field implementation.
* @see net.rim.device.api.ui.Field#layout(int, int)
*/
protected void layout(int width, int height) {
setExtent(Math.min( width, getPreferredWidth()),
Math.min( height, getPreferredHeight()));
}
/**
* Field implementation.
* @see net.rim.device.api.ui.Field#paint(Graphics)
*/
protected void paint(Graphics graphics){
// First draw the background colour and picture
graphics.setColor(this.color);
graphics.fillRect(0, 0, getWidth(), getHeight());
graphics.drawBitmap(0, 0, getWidth(), getHeight(), _currentPicture, 0, 0);
// Then draw the text
graphics.setColor(Color.BLACK);
graphics.setFont(_font);
graphics.drawText(_label, 4, 2,
(int)( getStyle() & DrawStyle.ELLIPSIS | DrawStyle.HALIGN_MASK ),
getWidth() - 6 );
}
/**
* Overridden so that the Event Dispatch thread can catch this event
* instead of having it be caught here..
* @see net.rim.device.api.ui.Field#navigationClick(int, int)
*/
protected boolean navigationClick(int status, int time){
fieldChangeNotify(1);
return true;
}
}
回答2:
You can use:
UiApplication.getUiApplication().pushScreen(new HomeScreen());
If your application is not doing anything strange UiApplication.getUiApplication() will always return the UiApplication object for your program. This is a singleton object created for each UiApplication context.
You could also use:
UserInterface.getUiApplication().pushScreen(new HomeScreen());
If the UserInterface class is visible to the class you are working on, but this would make your code less re-usable.
I've collected some basic samples on my blog. Have a look at this page. Start at the bottom and work your way up.
回答3:
Try the following code I have added UserInterfaceScreen. When UserInterfaceScreen is constructed, it adds a CustomMenuButtonField and sets a field change listener. When the button is clicked it pushes the new screen to the stack
package mypackage;
import net.rim.device.api.ui.UiApplication;
public class UserInterface extends UiApplication {
public static void main(String[] args){
UserInterface theApp = new UserInterface();
theApp.enterEventDispatcher();
}
public UserInterface() {
pushScreen(new UserInterfaceScreen());
}
}
This is the UserInterfaceScreen
package mypackage;
import net.rim.device.api.ui.Field;
import net.rim.device.api.ui.FieldChangeListener;
import net.rim.device.api.ui.UiApplication;
import net.rim.device.api.ui.container.MainScreen;
public class UserInterfaceScreen extends MainScreen {
public UserInterfaceScreen() {
super();
//replace null with the image string
CustomMenuButtonField button = new CustomMenuButtonField(null, null);
button.setChangeListener(new FieldChangeListener() {
public void fieldChanged(Field field, int context) {
UiApplication.getUiApplication().pushScreen(new MyHomeScreen());
}
});
}
}
回答4:
Look the answer in the below link which I posted by me(alishaik786) :
Clickable Bitmap;
来源：https://stackoverflow.com/questions/9035987/calling-between-classes-in-blackberry-java