具有固定大小的黑莓 VerticalFieldManager : Scroll issue

Question

我试图拥有一个带有修复标题(带有一些字段的管理器)和可滚动内容(自定义字段列表)的全屏用户界面。这个想法是模拟一种可滚动列表。

为此，我制作了一个自定义 VerticalFieldManager，它接受 maxHeight(屏幕高度 - 标题高度)。

我遇到了以下问题:

• 滚动箭头(永远)不显示
• 在 OS 4.7 (Storm) 上，我可以向下滚动到最后一项，直到屏幕上除了标题之外没有任何内容。

我的代码需要使用 JDE 4.2.1 和 4.7 进行编译并在 Pearl 和 Storm 上运行。 (最坏的情况下我可以有这个类的两个版本)

我怀疑这两个问题是相关的。我可能做错了什么。我查看了一些示例/论坛，总是找到类似的解决方案/代码。你们能告诉我我做错了什么吗？

/**
 *  custom class, so we can set a max height (to keep the header visible)
 */
class myVerticalFieldManager extends VerticalFieldManager{
private int maxHeight = 0;

myVerticalFieldManager(int _maxHeight){
  super(
   //this provoc an "empty scrollable zone" on Storm
   // but if you don't put it, on other OS, the vertical manager does not scroll at all.
   Manager.VERTICAL_SCROLL 

   | Manager.VERTICAL_SCROLLBAR
   ); 
  maxHeight = _maxHeight;
}


protected void sublayout(int width, int height){
        super.sublayout(width, getPreferredHeight());
        setExtent(width, getPreferredHeight());
}

public int getPreferredWidth() {
    return Graphics.getScreenWidth();
}

/**
 * allow the manager to use all the given height. (vs auto Height)
 */
public boolean forceMaxHeight = false;
public int getPreferredHeight() {
  if (forceMaxHeight) return maxHeight;
  int m = super.getPreferredHeight();
  if (m > maxHeight) m = maxHeight;
  return m;   
}    

////////////////////////////////////////////////////////////////////////////

protected boolean isUpArrowShown(){
  //TODO: does not seem to work (4.2.1 emulator & 4.5 device). (called with good return value but the arrows are not painted)
  int i = getFieldWithFocusIndex();
  //Trace("isUpArrowShown " + i);
  return i > 0;
  // note: algo not correct, cause the up arrow will be visible event when no field are hidden.
  //       but not so bad, so the user "know" that he can go up.
}

protected boolean isDownArrowShown(){
  int i = getFieldWithFocusIndex();
  return i < getFieldCount();
}

////////////////////////////////////////////////////////////////////////////
// note : since 4.6 you can use
// http://www.blackberry.com/developers/docs/4.6.0api/net/rim/device/api/ui/decor/Background.html

public int myBackgroundColor = 0xffffff;
protected void paint(Graphics g){
    g.setBackgroundColor(myBackgroundColor);
    // Clears the entire graphic area to the current background
    g.clear();
    super.paint(g);
}


} 

欢迎任何帮助。

Answer 1

所以，

我为 STORM 上的“空白可滚动区域”问题提供了此解决方法它很丑陋，并且不允许自定义 ScrollChangeListener，但它可以在 Pearl & Storm 上使用

implements ScrollChangeListener

 //in constructor:

  setScrollListener(null);
  setScrollListener(this);


private boolean MY_CHANGING_SCROLL = false;
public void scrollChanged(Manager manager, int newHorizontalScroll, int newVerticalScroll){
  if (!MY_CHANGING_SCROLL){
    MY_CHANGING_SCROLL = true;
    myCheckVerticalScroll();
    MY_CHANGING_SCROLL = false;
  }      
}  


protected int myMaxVerticalScrollPosition(){
  int vh = getVirtualHeight();
  int h = getHeight();
  if (vh < h ) return 0; // no scroll
  return vh - h; // don't scroll lower than limit.
}

protected void invCheckVerticalScroll() {
    int i = getVerticalScroll();
    int m = myMaxVerticalScrollPosition();
    if ( i > m){
        i = m;
        setVerticalScroll(i);
    }
}

我仍在寻找滚动箭头问题的解决方案......如果有人有想法...