差异柱形图（Diff Column Chart）

以下是显示差异的柱形图的示例。

我们已经在Google Charts Configuration Syntax一章中看到了用于绘制图表的配置 。 现在，让我们看一个显示差异的柱形图的示例。

配置 (Configurations)

我们使用ColumnChart类来显示柱形图，显示差异。

// column chart
ColumnChart chart = new ColumnChart();

例子 (Example)

HelloWorld.java

package cn.xnip.client;
import com.google.gwt.core.client.EntryPoint;
import com.google.gwt.user.client.ui.RootPanel;
import com.googlecode.gwt.charts.client.ChartLoader;
import com.googlecode.gwt.charts.client.ChartPackage;
import com.googlecode.gwt.charts.client.ColumnType;
import com.googlecode.gwt.charts.client.DataTable;
import com.googlecode.gwt.charts.client.corechart.ColumnChart;
public class HelloWorld implements EntryPoint {
   private ColumnChart chart;
   private void initialize() {
      ChartLoader chartLoader = new ChartLoader(ChartPackage.CORECHART);
      chartLoader.loadApi(new Runnable() {
         public void run() {
            // Create and attach the chart
            chart = new ColumnChart();
            RootPanel.get().add(chart);
            draw();
         }
      });
   }
   private void draw() {
      DataTable current = DataTable.create();
      current.addColumn(ColumnType.STRING, "Name");
      current.addColumn(ColumnType.NUMBER, "Score");
      current.addRow("Jane", 900);
      current.addRow("Joe", 1000);
      current.addRow("Janet", 1170);
      current.addRow("Robert", 1250);
      current.addRow("Julie", 1530);    
      // Prepare the data
      DataTable older = DataTable.create();
      older.addColumn(ColumnType.STRING, "Name");
      older.addColumn(ColumnType.NUMBER, "Score");
      older.addRow("Jane", 400);
      older.addRow("Joe", 700);
      older.addRow("Janet", 970);
      older.addRow("Robert", 1000);
      older.addRow("Julie", 1100);    		
      // Draw the chart
      chart.draw(chart.computeDiff(older, current));
      chart.setWidth("400px");
      chart.setHeight("400px");
   }
   public void onModuleLoad() {
      initialize();
   }
}

结果 (Result)

验证结果。