Blackberry 黑莓手机背景为黑色时，ObjectChoiceField标签为何隐藏

我使用的是ObjectChoiceField，当我使用黑色背景时，实际上我的标签是隐藏的？我使用的是这个示例

我的文本是“星期几”是否因黑色背景而隐藏？ 如何为给定标签*“周中的某一天”留出一定的余量

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回答这里？我的第二个问题是如何设置边距。如果我想在左边显示标签side@user2648752左边的意思是。。？？？我可以再解释一下。

package mypackage;

import net.rim.device.api.system.Display;
import net.rim.device.api.ui.Color;
import net.rim.device.api.ui.Graphics;
import net.rim.device.api.ui.component.ButtonField;
import net.rim.device.api.ui.component.ObjectChoiceField;
import net.rim.device.api.ui.container.MainScreen;
import net.rim.device.api.ui.container.VerticalFieldManager;

/**
 * A class extending the MainScreen class, which provides default standard
 * behavior for BlackBerry GUI applications.
 */
public final class MyScreen extends MainScreen
{
    /**
     * Creates a new MyScreen object
     */
    public MyScreen()
    {        
        // Set the displayed title of the screen       
        setTitle("Drop-down List Demo"); 
        String choices[] = {"Monday","Tuesday","Wednesday","Thursday","Friday","Saturday","Sunday"};
        int iSetTo = 0;
        VerticalFieldManager vfm=new VerticalFieldManager(){
            protected void paint(Graphics graphics) {
                // TODO Auto-generated method stub
                graphics.setBackgroundColor(Color.BLACK);
                graphics.fillRect(0, 0, Display.getWidth(), 800);
                super.paint(graphics);
            }
        };
        vfm.add(new ObjectChoiceField("Day of the week",choices,iSetTo){
            protected void paint(Graphics graphics) {
                // TODO Auto-generated method stub
                graphics.setBackgroundColor(Color.WHITE);

                super.paint(graphics);
            }
        });



        add(vfm);

    }
}