黑莓VerticalFieldManager固定大小：滚动发行 [英] Blackberry VerticalFieldManager with fixed size : Scroll issue

问题描述

我想有一个固定头部（某些字段经理）和一个滚动的内容（自定义字段列表）全屏UI。这样做是为了模拟一种滚动列表的。

I'm trying to have a full screen UI with a fix header ( a manager with some fields) and a scrollable contents (a list of custom field). The idea is to emulate a kind of scrollable list.

有关这个我做了一个自定义的VerticalFieldManager是接受了maxHeight（屏幕高度 - 头部高度）。

For this I made a custom VerticalFieldManager that accept a maxHeight (the screen height - the header height).

我有以下问题：

• 滚动箭头不显示（永远）


• 在OS 4.7（暴风影音），我可以滚动比的最后一个项目，直至有我的屏幕，但头就没事。

我的code需要编译与JDE 4.2.1＆安培; 4.7以及珍珠和风暴运行。 （在最坏的情况，我可以有两个版本，这个类的）

My code need to compile with the JDE 4.2.1 & 4.7 and to run on Pearl and Storm. (at worst I could have two version of this class)

我怀疑这两个问题是相关的。我可能做错事。我看了看几个例子/论坛，总能找到类似的解决方案/ code。
难道你们可以告诉我，我做错了什么？

I suspect the two problems are related. I probably do something wrong. I looked at a few example/forum and always found similar solution/code. Do you guys can tell me what I did wrong?

/**
 *  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);
}


}

任何帮助是值得欢迎的。

any helps is welcome.

推荐答案

因此​​，

我来到这个解决方法上STORM空滚动区的问题
它的丑陋，不允许自定义ScrollChangeListener，但它的工作对珍珠放大器;风暴

I came with this workaround for the "empty scrollable zone" problem on STORM it's ugly and doesn't allow a custom ScrollChangeListener, but it's working on Pearl & Storm

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);
    }
}

我还在寻找一个解决方案，以滚动箭头的问题...
如果有人有一个想法......

I'm still looking for a solution to the scroll arrows problem... If anybody got an idea...

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