（译）Eclipse Zest一

1. Eclipse Zest

1.1 概述

Eclipse Zest是一个可视化的图形工具。它基于SWT/Draw2D。Zest还支持JFace中Viewer的概念，因此允许模型和视图的分离。这篇文章假设你已经熟悉了Eclipse RCP或Eclipse Plugin开发。

 

（我注：其实也可以在一个普通的SWT程序中使用Zest）

 

1.2 组件

Eclipse Zest有以下组件：

 

• GraphNode                --             graph中，带属性的结点
• GraphConnections     --             graph中，用来连接两个结点的边线
• GraphContainer         --             graph中，用来包含其他结点的容器
• Graph                         --             根，用来包含所有其他的结点（nodes，connections，container）

（我注：graph可以理解为画板，用来画这些结点的）

1.3 布局

Zest提供了一些布局管理器，用来决定怎么布局graph上的结点。下面列出的就是所提供的一些布局：

表1 布局管理器

 

 

TreeLayoutAlgorithm	Graph is displayed in the form of a vertical tree
HorizontalTreeLayoutAlgorithm	Similar to TreeLayoutAlgorithm, but layout is horizontal
RadialLayoutAlgorithm	Root is the center, the others nodes are placed around this node
GridLayoutAlgorithm SpringLayoutAlgorithm	layout the graph, so that all connections should have approx the same length and that the edges overlap minimal
HorizontalShift	move overlapping nodes to the right
CompositeLayoutAlgorithm	combines other layout algorithms, for example, HorizontalShift can be the second layout algorithm to move nodes which were still overlapping if another algorithm is used.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1.4 Filter

可以通过调用setFilter(filter)方法，在布局上增加过滤器（org.eclipse.zest.layouts.filter），用于决定哪些结点和边线是可见的。filter收到一个LayoutItem对象，实际的graph结点可以通过方法getGraphData()得到。

2. 安装

（我注：好像现在安装完GEF后，自动就有了，所以这里略了）

3 你的第一个Zest工程

3.1 开始

创建一个Eclipse RCP应用“de.vogella.zest.first”。选择模板"Eclipse RCP with a view“。 增加"org.eclipse.zest.core" 和 "org.eclipse.zest.layouts" 依赖项。

 

修改"View.java"的代码如下，用于创建一个简单的graph和连接它的元素：

package de.vogella.zest.first;

import org.eclipse.swt.SWT;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.Listener;
import org.eclipse.ui.part.ViewPart;
import org.eclipse.zest.core.widgets.Graph;
import org.eclipse.zest.core.widgets.GraphConnection;
import org.eclipse.zest.core.widgets.GraphNode;
import org.eclipse.zest.core.widgets.ZestStyles;
import org.eclipse.zest.layouts.LayoutStyles;
import org.eclipse.zest.layouts.algorithms.SpringLayoutAlgorithm;
import org.eclipse.zest.layouts.algorithms.TreeLayoutAlgorithm;

public class View extends ViewPart {
	public static final String ID = "de.vogella.zest.first.view";
	private Graph graph;
	private int layout = 1;

	public void createPartControl(Composite parent) {
		// Graph will hold all other objects
		graph = new Graph(parent, SWT.NONE);
		// Now a few nodes
		GraphNode node1 = new GraphNode(graph, SWT.NONE, "Jim");
		GraphNode node2 = new GraphNode(graph, SWT.NONE, "Jack");
		GraphNode node3 = new GraphNode(graph, SWT.NONE, "Joe");
		GraphNode node4 = new GraphNode(graph, SWT.NONE, "Bill");
		// Lets have a directed connection
		new GraphConnection(graph, ZestStyles.CONNECTIONS_DIRECTED, node1,
				node2);
		// Lets have a dotted graph connection
		new GraphConnection(graph, ZestStyles.CONNECTIONS_DOT, node2, node3);
		// Standard connection
		new GraphConnection(graph, SWT.NONE, node3, node1);
		// Change line color and line width
		GraphConnection graphConnection = new GraphConnection(graph, SWT.NONE,
				node1, node4);
		graphConnection.changeLineColor(parent.getDisplay().getSystemColor(
				SWT.COLOR_GREEN));
		// Also set a text
		graphConnection.setText("This is a text");
		graphConnection.setHighlightColor(parent.getDisplay().getSystemColor(
				SWT.COLOR_RED));
		graphConnection.setLineWidth(3);
		graphConnection.addListener(SWT.SELECTED, new Listener() {

			@Override
			public void handleEvent(Event event) {
				System.out.println("Selected");
			}

		});
		graph.setLayoutAlgorithm(new SpringLayoutAlgorithm(
				LayoutStyles.NO_LAYOUT_NODE_RESIZING), true);

	}

	public void setLayoutManager() {
		switch (layout) {
		case 1:
			graph.setLayoutAlgorithm(new TreeLayoutAlgorithm(
					LayoutStyles.NO_LAYOUT_NODE_RESIZING), true);
			layout++;
			break;
		case 2:
			graph.setLayoutAlgorithm(new SpringLayoutAlgorithm(
					LayoutStyles.NO_LAYOUT_NODE_RESIZING), true);
			layout = 1;
			break;

		}

	}

	/**
	 * Passing the focus request to the viewer's control.
	 */
	public void setFocus() {
	}
}

 

运行以后，得到下图：

3.2 通过command来改变布局

创建一个command，并把以下"de.vogella.zest.first.handler.ChangeLayout"作为它的handler，此handler用于更改布局。最后把这个command加到一个menu上：

package de.vogella.zest.first.handler;

import org.eclipse.core.commands.AbstractHandler;
import org.eclipse.core.commands.ExecutionEvent;
import org.eclipse.core.commands.ExecutionException;
import org.eclipse.ui.IViewPart;
import org.eclipse.ui.handlers.HandlerUtil;

import de.vogella.zest.first.View;

public class ChangeLayout extends AbstractHandler {

	@Override
	public Object execute(ExecutionEvent event) throws ExecutionException {
		IViewPart findView = HandlerUtil.getActiveWorkbenchWindow(event)
				.getActivePage().findView("de.vogella.zest.first.view");
		View view = (View) findView;
		view.setLayoutManager();
		return null;
	}

}

 运行应用，如果你选择了上面的菜单，视图的布局将会改变

4.Zest和JFace

JFace提供了viewers用于分离数据和展现。请看Eclipse JFace TableViewer 或 Eclipse JFace TreeViewer 。JFace要求一个content provider和一个label provider。Zest提供了一个"GraphViewer“作为一个viewer。content provider则是基于connections或者是nodes的。

 

标准的Zest content providers有：

Content Provider Description

IGraphContentProvider	Based on the connections. The connections contain the information which nodes they refer to. Cannot display nodes without connections.
IGraphEntityContentProvider	Based on the Node which contain the information about which relationship they have. These relationship are available in the label provider as EntityConnectionData objects.
IGraphEntityRelationshipContentProvider	Node based, the content provider defines getRelationShips(sourceNode, destinationNode) which determines the connections. The advantages compared with IGraphEntityContentProvider is that you decide which objects you return.

 

Zest的label provider可以是一个标准的JFace的 ILabelProvider，也可以是Zest特定的IEntityStyleProvider。