GEF的RootEditPart对应的Figure是一个由多个Layer组成的LayeredPane，每个Layer负责包含不同类型的图形元素，如节点、连接、网格线等等。所以要让图形编辑器显示一个图片作为背景，可以在它们其中一个层里绘制这个图片，也可以添加一个层专门放置背景图片。在gef中所有的图形元件继承自Figure类。实现背景色和背景图的更改的必须实现Figure中部分类。
由源代码：
/**用于绘制元件和元件内的子元件系列
* Paints this Figure and its children.
* @param graphics The Graphics object used for painting
* @see #paintFigure(Graphics)
* @see #paintClientArea(Graphics)
* @see #paintBorder(Graphics)
*/
publicvoid paint(Graphics graphics) {
if (getLocalBackgroundColor() != null)
graphics.setBackgroundColor(getLocalBackgroundColor());
if (getLocalForegroundColor() != null)
graphics.setForegroundColor(getLocalForegroundColor());
if (font != null)
graphics.setFont(font);
graphics.pushState();
try {
paintFigure(graphics);
graphics.restoreState();
paintClientArea(graphics);
paintBorder(graphics);
} finally {
graphics.popState();
}
}
/**用于绘制边框border对象
* Paints the border associated with this Figure, if one exists.
* @param graphics The Graphics used to paint
* @see Border#paint(IFigure, Graphics, Insets)
* @since 2.0
*/
protectedvoid paintBorder(Graphics graphics) {
if (getBorder() != null)
getBorder().paint(this, graphics, NO_INSETS);
}
/**用于绘制所有子元件对象
* Paints this Figure's children. The caller must save the state of the graphics prior to
* calling this method, such that <code>graphics.restoreState()</code> may be called
* safely, and doing so will return the graphics to its original state when the method was
* entered.
* <P>
* This method must leave the Graphics in its original state upon return.
* @param graphics the graphics used to paint
* @since 2.0
*/
protectedvoid paintChildren(Graphics graphics) {
IFigure child;
Rectangle clip = Rectangle.SINGLETON;
for (int i = 0; i < children.size(); i++) {
child = (IFigure)children.get(i);
if (child.isVisible() && child.intersects(graphics.getClip(clip))) {
graphics.clipRect(child.getBounds());
child.paint(graphics);
graphics.restoreState();
}
}
}
/**绘制子元件区域对象
* Paints this Figure's client area. The client area is typically defined as the anything
* inside the Figure's {@link Border} or {@link Insets}, and by default includes the
* children of this Figure. On return, this method must leave the given Graphics in its
* initial state.
* @param graphics The Graphics used to paint
* @since 2.0
*/
protectedvoid paintClientArea(Graphics graphics) {
if (children.isEmpty())
return;
boolean optimizeClip = getBorder() == null || getBorder().isOpaque();
if (useLocalCoordinates()) {
graphics.translate(
getBounds().x + getInsets().left,
getBounds().y + getInsets().top);
if (!optimizeClip)
graphics.clipRect(getClientArea(PRIVATE_RECT));
graphics.pushState();
paintChildren(graphics);
graphics.popState();
graphics.restoreState();
} else {
if (optimizeClip)
paintChildren(graphics);
else {
graphics.clipRect(getClientArea(PRIVATE_RECT));
graphics.pushState();
paintChildren(graphics);
graphics.popState();
graphics.restoreState();
}
}
}
/** 绘制元件的背景等信息
* Paints this Figure's primary representation, or background. Changes made to the
* graphics to the graphics current state will not affect the subsequent calls to {@link
* #paintClientArea(Graphics)} and {@link #paintBorder(Graphics)}. Furthermore, it is safe
* to call <code>graphics.restoreState()</code> within this method, and doing so will
* restore the graphics to its original state upon entry.
* @param graphics The Graphics used to paint
* @since 2.0
*/
protectedvoid paintFigure(Graphics graphics) {
if (isOpaque())
graphics.fillRectangle(getBounds());
if (getBorder() instanceof AbstractBackground)
((AbstractBackground) getBorder()).paintBackground(this, graphics, NO_INSETS);
}
由上面的源代码可以看出：
/**
* 用来定制GraphicalViewer的各种信息
* 在这两个方法里我们配置了RootEditPart、用于创建 EditPart的EditPartFactory、
* Contents即Diagram对象和增加了拖放支持，拖动目标是当前 EditPartViewer，后面会看到拖动源就是调色板。
*/
/**
* 用来定制GraphicalViewer的各种信息
* 在这两个方法里我们配置了RootEditPart、用于创建 EditPart的EditPartFactory、
* Contents即Diagram对象和增加了拖放支持，拖动目标是当前 EditPartViewer，后面会看到拖动源就是调色板。
*/
@Override
protectedvoid configureGraphicalViewer() {
super.configureGraphicalViewer();
//添加背景图片
this.getGraphicalViewer().setRootEditPart(new ScalableFreeformRootEditPart(){
//可以注入自己设定的层
@Override
protected LayeredPane createPrintableLayers(){
LayeredPane layeredPane= super.createPrintableLayers();
layeredPane.add(new FreeformLayer(),PRIMARY_LAYER);
//可以添加自定一的层layer接口定义
layeredPane.add(new FreeformLayer(),CONNECTION_LAYER);
return layeredPane;
}
//添加背景色和背景图
@Override
protectedvoid createLayers(LayeredPane layeredPane) {
Layer layer=new FreeformLayer(){
protected