MPAndroidChart

allprojects {
    repositories {
        maven { url 'https://jitpack.io' }
    }
}

dependencies {
    implementation 'com.github.PhilJay:MPAndroidChart:v3.0.3'
}

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
   xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent"
   android:layout_height="match_parent">

    <!-- Add a Horizontal Bar Chart using MPAndroidChart library -->
    <com.github.mikephil.charting.charts.HorizontalBarChart
       android:id="@+id/skill_rating_chart"
       android:layout_width="match_parent"
       android:layout_height="match_parent" />

</android.support.constraint.ConstraintLayout>

class MainActivity : Activity {

   lateinit var skillRatingChart : HorizontalBarChart

   override fun onCreate(savedInstanceState: Bundle?) {
       super.onCreate(savedInstanceState)
       setContentView(R.layout.chart)

       setSkillGraph( )

   }
}

/**
* Set up the axes along with other necessary details for the horizontal bar chart.
*/
fun setSkillGraph(){
   skillRatingChart = skill_rating_chart              //skill_rating_chart is the id of the XML layout

   skillRatingChart.setDrawBarShadow(false)
   val description = Description()
   description.text = ""
   skillRatingChart.description = description
   skillRatingChart.legend.setEnabled(false)
   skillRatingChart.setPinchZoom(false)
   skillRatingChart.setDrawValueAboveBar(false)

   //Display the axis on the left (contains the labels 1*, 2* and so on)
   val xAxis = skillRatingChart.getXAxis()
   xAxis.setDrawGridLines(false)
   xAxis.setPosition(XAxis.XAxisPosition.BOTTOM)
   xAxis.setEnabled(true)
   xAxis.setDrawAxisLine(false)


   val yLeft = skillRatingChart.axisLeft

//Set the minimum and maximum bar lengths as per the values that they represent
   yLeft.axisMaximum = 100f
   yLeft.axisMinimum = 0f
   yLeft.isEnabled = false

   //Set label count to 5 as we are displaying 5 star rating
   xAxis.setLabelCount(5)

//Now add the labels to be added on the vertical axis
   val values = arrayOf("1 *", "2 *", "3 *", "4 *", "5 *")
   xAxis.valueFormatter = XAxisValueFormatter(values)        

   val yRight = skillRatingChart.axisRight
   yRight.setDrawAxisLine(true)
   yRight.setDrawGridLines(false)
   yRight.isEnabled = false

   //Set bar entries and add necessary formatting
   setGraphData()

   //Add animation to the graph
   skillRatingChart.animateY(2000)
}

public class XAxisValueFormatter implements IAxisValueFormatter {

   private String[] values;

   public XAxisValueFormatter(String[] values) {
       this.values = values;
   }

   @Override
   public String getFormattedValue(float value, AxisBase axis) {
       // "value" represents the position of the label on the axis (x or y)
       return this.values[(int) value];
   }

}

/**
* Set the bar entries i.e. the percentage of users who rated the skill with
* a certain number of stars.
*
* Set the colors for different bars and the bar width of the bars.
*/
private fun setGraphData() {

   //Add a list of bar entries
   val entries = ArrayList<BarEntry>()
   entries.add(BarEntry(0f, 27f))
   entries.add(BarEntry(1f, 45f))
   entries.add(BarEntry(2f, 65f))
   entries.add(BarEntry(3f, 77f))
   entries.add(BarEntry(4f, 93f))

  //Note : These entries can be replaced by real-time data, say, from an API

  ......

}

val barDataSet = BarDataSet(entries, "Bar Data Set")

private fun setGraphData() {
    .....

   //Set the colors for bars with first color for 1*, second for 2* and so on
      barDataSet.setColors(
              ContextCompat.getColor(skillRatingChart.context, R.color.md_red_500),
              ContextCompat.getColor(skillRatingChart.context, R.color.md_deep_orange_400),
              ContextCompat.getColor(skillRatingChart.context, R.color.md_yellow_A700),
              ContextCompat.getColor(skillRatingChart.context, R.color.md_green_700),
              ContextCompat.getColor(skillRatingChart.context, R.color.md_indigo_700)

   .....
)

//Set bar shadows
   skillRatingChart.setDrawBarShadow(true)
   barDataSet.barShadowColor = Color.argb(40, 150, 150, 150)
   val data = BarData(barDataSet)

   //Set the bar width
   //Note : To increase the spacing between the bars set the value of barWidth to < 1f
   data.barWidth = 0.9f

   //Finally set the data and refresh the graph
   skillRatingChart.data = data
   skillRatingChart.invalidate()
}