Google Charts provides a way to dynamically render data through different visualizations. Combined with Visualforce, the Google Charts can offer more flexibility and distribution potential than using a dashboard. Since the charts are generated through a URL, the visualizations can be shared and embedded wherever images are permitted.
There are two prerequisites before using the Google Charts API. The first is to determine how to encode the data. The Google Charts API has three data encoding types—text, simple, and extended. For this example, we'll only use the simple encoding. The second is to decide what type of chart to use. For this example, a user will choose between a bar graph or a line chart.
/* This class contains the encoding algorithm for use with the Google chartAPI. */ public class GoogleDataEncoding { // Exceptions to handle any erroneous data public class EncodingException extends Exception {} public class UnsupportedEncodingTypeException extends Exception {} /* The encoding map which takes an integer key and returns the respective encoding value as defined by Google. This map is initialized in init() */ private Map<Integer, String> encodingMap { get; set; } /* The maximum encoding value supported for the given encoding type. This value is set during init() */ private Integer encodingMax { get; set; } /* The minimum encoding value supported for the given encoding type. This value is set during init() */ private Integer encodingMin { get; set; } /* The encoding type according to Google's API. Only SIMPLE is implemented. */ public enum EncodingType { TEXT, SIMPLE, EXTENDED } /* The minimum value to use in the generation of an encoding value. */ public Integer min { get; private set; } /* The maximum value to use in the generation of an encoding value. */ public Integer max { get; private set; } // The encoding type according to the API defined by Google public EncodingType eType { get; private set; } // Corresponds to the data set provided by the page public String dataSet { get; set; } // Corresponds to the type of graph selected on the page public String graph { get; set; } // The URL that renders the Google Chart public String chartURL { get; set; } // Indicates whether the chart should be displayed public Boolean displayChart { get; set; } public GoogleDataEncoding() { min = 0; max = 61; eType = EncodingType.SIMPLE; displayChart = false; init(); } public PageReference create() { String[] dataSetList = dataSet.split(',', 0); String mappedValue = 'chd=s:'; chartURL = 'http://chart.apis.google.com/chart?chs=600x300' + '&chtt=Time+vs|Distance&chxt=x,y,x,y' + '&chxr=0,0,10,1|1,0,65,5' + '&chxl=2:|Seconds|3:|Meters'; if (graph.compareTo('barChart') == 0) { chartURL += '&cht=bvs'; } else if (graph.compareTo('lineChart') == 0) { chartURL += '&cht=ls'; } else { throw new EncodingException('An unsupported chart type' + 'was selected: ' + graph + ' does not exist.'); } for(String dataPoint : dataSetList) { mappedValue += getEncode(Integer.valueOf(dataPoint.trim())); } chartURL += '&' + mappedValue; displayChart = true; return null; } /* This method returns the encoding type parameter value that matches the specified encoding type. */ public static String getEncodingDescriptor(EncodingType t) { if(t == EncodingType.TEXT) return 't'; else if(t == EncodingType.SIMPLE) return 's'; else if(t == EncodingType.EXTENDED) return 'e'; else return ''; } /* This method takes a given number within the declared range of the encoding class and encodes it according to the encoding type. If the value provided fall outside of the declared range, an EncodingException is thrown. */ public String getEncode(Integer d) { if(d > max || d < min) { throw new EncodingException('Value provided ' + d + ' was outside the declared min/max range (' + min + '/' + max + ')'); } else { return encodingMap.get(d); } } /* This method initializes the encoding map which is then stored for expected repetitious use to minimize statement invocation. */ private void init() { if(eType == EncodingType.SIMPLE) { encodingMax = 61; encodingMin = 0; encodingMap = new Map<Integer, String>(); encodingMap.put(0,'A'); encodingMap.put(1,'B'); encodingMap.put(2,'C'); encodingMap.put(3,'D'); encodingMap.put(4,'E'); encodingMap.put(5,'F'); encodingMap.put(6,'G'); encodingMap.put(7,'H'); encodingMap.put(8,'I'); encodingMap.put(9,'J'); encodingMap.put(10,'K'); encodingMap.put(11,'L'); encodingMap.put(12,'M'); encodingMap.put(13,'N'); encodingMap.put(14,'O'); encodingMap.put(15,'P'); encodingMap.put(16,'Q'); encodingMap.put(17,'R'); encodingMap.put(18,'S'); encodingMap.put(19,'T'); encodingMap.put(20,'U'); encodingMap.put(21,'V'); encodingMap.put(22,'W'); encodingMap.put(23,'X'); encodingMap.put(24,'Y'); encodingMap.put(25,'Z'); encodingMap.put(26,'a'); encodingMap.put(27,'b'); encodingMap.put(28,'c'); encodingMap.put(29,'d'); encodingMap.put(30,'e'); encodingMap.put(31,'f'); encodingMap.put(32,'g'); encodingMap.put(33,'h'); encodingMap.put(34,'i'); encodingMap.put(35,'j'); encodingMap.put(36,'k'); encodingMap.put(37,'l'); encodingMap.put(38,'m'); encodingMap.put(39,'n'); encodingMap.put(40,'o'); encodingMap.put(41,'p'); encodingMap.put(42,'q'); encodingMap.put(43,'r'); encodingMap.put(44,'s'); encodingMap.put(45,'t'); encodingMap.put(46,'u'); encodingMap.put(47,'v'); encodingMap.put(48,'w'); encodingMap.put(49,'x'); encodingMap.put(50,'y'); encodingMap.put(51,'z'); encodingMap.put(52,'0'); encodingMap.put(53,'1'); encodingMap.put(54,'2'); encodingMap.put(55,'3'); encodingMap.put(56,'4'); encodingMap.put(57,'5'); encodingMap.put(58,'6'); encodingMap.put(59,'7'); encodingMap.put(60,'8'); encodingMap.put(61,'9'); } } }
<apex:page controller="GoogleDataEncoding"> <apex:form > <apex:pageBlock title="Create a Google Chart for Time and Distance"> <apex:outputLabel value="Enter data set, separated by commas: " for="dataInput"/><br/> <apex:inputTextArea id="dataInput" title="First Data Point" value="{!dataSet}" rows="3" cols="50"/><br/> <apex:selectRadio value="{!graph}" layout="pageDirection"> <apex:selectOption itemValue="barChart" itemLabel="Horizontal Bar Chart"/> <apex:selectOption itemValue="lineChart" itemLabel="Line Chart"/> </apex:selectRadio> <apex:commandButton action="{!create}" value="Create"/> </apex:pageBlock> </apex:form> <apex:image url="{!chartURL}" alt="Sample chart" rendered="{!displayChart}"/> </apex:page>