1. WIKI教程
2. 了解GWT Google Charts
3. Crosshairs

Crosshairs

以下是在选择数据点时出现十字准线的基本折线图示例。

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，让我们看一个带十字准线的基本折线图的示例。

配置 (Configurations)

我们使用crosshair配置来设置十字准线。

Crosshair crosshair = Crosshair.create();
crosshair.setColor("#000000");
crosshair.setTrigger(CrosshairTrigger.SELECTION);
options.setCrosshair(crosshair);

例子 (Example)

HelloWorld.java

package com.iowiki.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.LineChart;
import com.googlecode.gwt.charts.client.corechart.LineChartOptions;
import com.googlecode.gwt.charts.client.options.Crosshair;
import com.googlecode.gwt.charts.client.options.CrosshairTrigger;
import com.googlecode.gwt.charts.client.options.HAxis;
import com.googlecode.gwt.charts.client.options.VAxis;
public class HelloWorld implements EntryPoint {
   private LineChart chart;
   private void initialize() {
      ChartLoader chartLoader = new ChartLoader(ChartPackage.CORECHART);
      chartLoader.loadApi(new Runnable() {
         public void run() {
            // Create and attach the chart
            chart = new LineChart();
            RootPanel.get().add(chart);
            draw();
         }
      });
   }
   private void draw() {
      // Prepare the data
      DataTable data = DataTable.create();
      data.addColumn(ColumnType.STRING, "Month");
      data.addColumn(ColumnType.NUMBER, "Tokyo");
      data.addColumn(ColumnType.NUMBER, "New York");
      data.addColumn(ColumnType.NUMBER, "Berlin");
      data.addColumn(ColumnType.NUMBER, "Berlin");
      data.addRow("Jan",  7.0, -0.2, -0.9, 3.9);
      data.addRow("Feb",  6.9, 0.8, 0.6, 4.2);
      data.addRow("Mar",  9.5,  5.7, 3.5, 5.7);
      data.addRow("Apr",  14.5, 11.3, 8.4, 8.5);
      data.addRow("May",  18.2, 17.0, 13.5, 11.9);
      data.addRow("Jun",  21.5, 22.0, 17.0, 15.2);
      data.addRow("Jul",  25.2, 24.8, 18.6, 17.0);
      data.addRow("Aug",  26.5, 24.1, 17.9, 16.6);
      data.addRow("Sep",  23.3, 20.1, 14.3, 14.2);
      data.addRow("Oct",  18.3, 14.1, 9.0, 10.3);
      data.addRow("Nov",  13.9,  8.6, 3.9, 6.6);
      data.addRow("Dec",  9.6,  2.5,  1.0, 4.8);
      // Set options
      LineChartOptions options = LineChartOptions.create();
      options.setTitle("Average Temperatures of Cities");
      options.setHAxis(HAxis.create("Month"));
      options.setVAxis(VAxis.create("Temperature"));
      Crosshair crosshair = Crosshair.create();
      crosshair.setColor("#000000");
      crosshair.setTrigger(CrosshairTrigger.SELECTION);
      options.setCrosshair(crosshair);
      // Draw the chart
      chart.draw(data,options);
      chart.setWidth("400px");
      chart.setHeight("400px");
   }
   public void onModuleLoad() {
      initialize();
   }
}

结果 (Result)

验证结果。