我需要在 BlackBerry 中进行如下自定义布局。
我在 Android 中做了同样的布局。现在我需要在 BlackBerry 中使用相同的布局。我是 BlackBerryapp 开发的新手。 BlackBerry 的 Fields 像 Android 中的 Views 对我来说似乎很混乱。
我尝试将VerticalFieldManager 和HorizontalFieldManager 与BitmapField 和LabelField 混合以生成我的布局。
我特别失败了将LabelField 放在屏幕底部。我用USE_ALL_HEIGHT & FIELD_BOTTOM 样式放在底部，但是滚动很长时间后才显示。
我的要求是当我的中间列表滚动时，页眉和页脚应该不滚动。
【问题讨论】：
标签： blackberry java-me
添加不随着屏幕中间的内容滚动的页眉和页脚字段的最简单方法是使用MainScreen#setBanner() 和MainScreen#setStatus()。下面是一个示例：
public class HeaderFooterListScreen extends MainScreen {
private static final int BG_COLOR = Color.BLACK;
private static final int HIGHLIGHT_COLOR = Color.BLUE;
private static final int FONT_COLOR = Color.WHITE;
private static final int ROW_HEIGHT = 60;
private Object[] _rowData;
private Field _header;
private Field _footer;
private Field _spacer;
private int _orientation;
public HeaderFooterListScreen() {
super(MainScreen.VERTICAL_SCROLL | MainScreen.VERTICAL_SCROLLBAR);
Background bg = BackgroundFactory.createSolidBackground(BG_COLOR);
setBackground(bg);
getMainManager().setBackground(bg);
// header
Bitmap headerImg = Bitmap.getBitmapResource("header.png");
_header = new BitmapField(headerImg);
setBanner(_header);
// list
_rowData = new Object[] { "row one", "row two", "row three" }; //, "row four", "row five", "row six", "row seven", "row eight", "row nine", "row ten" };
ListField list = new ListField();
int c = Color.RED;
XYEdges edgeColors = new XYEdges(c, c, c, c);
XYEdges edgeThicknesses = new XYEdges(5, 5, 5, 5);
list.setBorder(BorderFactory.createSimpleBorder(edgeThicknesses, edgeColors, Border.STYLE_SOLID));
list.setCallback(new CustomListFieldCallback());
list.setRowHeight(ROW_HEIGHT);
list.setSize(_rowData.length);
add(list);
// footer
_footer = new LabelField("Footer Showing Status As Text", Field.USE_ALL_WIDTH | DrawStyle.HCENTER) {
public void paint(Graphics g) {
// change font color
int oldColor = g.getColor();
g.setColor(FONT_COLOR);
super.paint(g);
g.setColor(oldColor);
}
};
_footer.setFont(_footer.getFont().derive(Font.PLAIN, 24));
setStatus(_footer);
}
private void centerList() {
if (_spacer != null && _spacer.getManager() != null) {
// delete the old spacer field, if there was one
delete(_spacer);
}
int listHeight = _rowData.length * ROW_HEIGHT;
int availableHeight = getHeight() - _footer.getHeight() - _header.getHeight();
if (availableHeight > listHeight) {
boolean firstRun = (_spacer == null);
// add a spacer above the list to force it down enough to be centered
final int SPACE = (availableHeight - listHeight) / 2;
_spacer = new Field() {
protected void layout(int width, int height) {
setExtent(width, SPACE);
}
protected void paint(Graphics graphics) {
}
};
insert(_spacer, 0);
if (firstRun) {
getMainManager().setVerticalScroll(0);
}
}
}
// called when device orientation changes
protected void sublayout(int width, int height) {
super.sublayout(width, height);
if (_orientation != Display.getOrientation()) {
_orientation = Display.getOrientation();
// run with invokeLater() to avoid recursive sublayout() calls
UiApplication.getUiApplication().invokeLater(new Runnable() {
public void run() {
// TODO: may have to adjust header, too?
centerList();
}
});
}
}
private class CustomListFieldCallback implements ListFieldCallback {
private final int PAD = 10;
public void drawListRow(ListField listField, Graphics graphics,
int index, int y, int width) {
int oldColor = graphics.getColor();
if (listField.getSelectedIndex() == index) {
graphics.setColor(HIGHLIGHT_COLOR);
} else {
graphics.setColor(BG_COLOR);
}
graphics.fillRect(0, y, width, listField.getRowHeight());
graphics.setColor(FONT_COLOR);
String text = (String)get(listField, index);
graphics.drawText(text, PAD, y + PAD, DrawStyle.LEFT);
graphics.setColor(oldColor);
}
public Object get(ListField listField, int index) {
return _rowData[index];
}
public int getPreferredWidth(ListField listField) {
return Display.getWidth();
}
public int indexOfList(ListField listField, String prefix, int start) {
return -1; // TODO?
}
}
}
你没有具体说明你希望中间的列表如何工作，所以我只是做了一些猜测。我也不确定红色边框是你想要的，还是你用来描述布局的东西。如果您对列表有更多要求，请编辑您的问题或发布新问题。
如果您来自 Android，并且不清楚 BlackBerry UI 类（例如 Fields 和 Managers）的作用，这里有一些资源：
【讨论】：
sublayout() 中添加了代码来检测方向变化，并调整间隔字段，因为横向需要更小的间隔。希望这会有所帮助。