[Feature] set gradient color for bar chart

MPChartExample/src/com/xxmassdeveloper/mpchartexample/BarChartActivity.java

@@ -4,6 +4,7 @@
 import android.annotation.SuppressLint;
 import android.graphics.RectF;
 import android.os.Bundle;
+import android.support.v4.content.ContextCompat;
 import android.util.Log;
 import android.view.Menu;
 import android.view.MenuItem;
@@ -16,7 +17,6 @@
 import com.github.mikephil.charting.charts.BarChart;
 import com.github.mikephil.charting.components.Legend;
 import com.github.mikephil.charting.components.Legend.LegendForm;
-import com.github.mikephil.charting.components.Legend.LegendPosition;
 import com.github.mikephil.charting.components.XAxis;
 import com.github.mikephil.charting.components.XAxis.XAxisPosition;
 import com.github.mikephil.charting.components.YAxis;
@@ -265,6 +265,9 @@ private void setData(int count, float range) {
             set1.setDrawIcons(false);
 
             set1.setColors(ColorTemplate.MATERIAL_COLORS);
+            int startColor = ContextCompat.getColor(this, android.R.color.holo_blue_dark);
+            int endColor = ContextCompat.getColor(this, android.R.color.holo_blue_bright);
+            set1.setGradientColor(startColor, endColor);
 
             ArrayList<IBarDataSet> dataSets = new ArrayList<IBarDataSet>();
             dataSets.add(set1);

MPChartLib/src/main/java/com/github/mikephil/charting/data/BaseDataSet.java

@@ -13,6 +13,7 @@
 import com.github.mikephil.charting.utils.ColorTemplate;
 import com.github.mikephil.charting.utils.MPPointF;
 import com.github.mikephil.charting.utils.Utils;
+import com.github.mikephil.charting.model.GradientColor;
 
 import java.lang.annotation.Documented;
 import java.lang.annotation.Inherited;
@@ -31,6 +32,8 @@ public abstract class BaseDataSet<T extends Entry> implements IDataSet<T> {
      */
     protected List<Integer> mColors = null;
 
+    protected GradientColor gradientColor = null;
+
     /**
      * List representing all colors that are used for drawing the actual values for this DataSet
      */
@@ -139,6 +142,11 @@ public int getColor() {
         return mColors.get(0);
     }
 
+    @Override
+    public GradientColor getGradientColor() {
+        return gradientColor;
+    }
+
     @Override
     public int getColor(int index) {
         return mColors.get(index % mColors.size());
@@ -219,6 +227,16 @@ public void setColor(int color) {
         mColors.add(color);
     }
 
+    /**
+     * Sets the start and end color for gradient colot, ONLY color that should be used for this DataSet.
+     *
+     * @param startColor
+     * @param endColor
+     */
+    public void setGradientColor(int startColor, int endColor) {
+        gradientColor = new GradientColor(startColor, endColor);
+    }
+
     /**
      * Sets a color with a specific alpha value.
      *

MPChartLib/src/main/java/com/github/mikephil/charting/interfaces/datasets/IDataSet.java

@@ -10,6 +10,7 @@
 import com.github.mikephil.charting.data.Entry;
 import com.github.mikephil.charting.formatter.IValueFormatter;
 import com.github.mikephil.charting.utils.MPPointF;
+import com.github.mikephil.charting.model.GradientColor;
 
 import java.util.List;
 
@@ -285,6 +286,13 @@ public interface IDataSet<T extends Entry> {
      */
     int getColor();
 
+    /**
+     * Returns the Gradient color model
+     *
+     * @return
+     */
+    GradientColor getGradientColor();
+
     /**
      * Returns the color at the given index of the DataSet's color array.
      * Performs a IndexOutOfBounds check by modulus.

MPChartLib/src/main/java/com/github/mikephil/charting/model/GradientColor.java

@@ -0,0 +1,28 @@
+package com.github.mikephil.charting.model;
+
+public class GradientColor {
+
+    private int startColor;
+    private int endColor;
+
+    public GradientColor(int startColor, int endColor) {
+        this.startColor = startColor;
+        this.endColor = endColor;
+    }
+
+    public int getStartColor() {
+        return startColor;
+    }
+
+    public void setStartColor(int startColor) {
+        this.startColor = startColor;
+    }
+
+    public int getEndColor() {
+        return endColor;
+    }
+
+    public void setEndColor(int endColor) {
+        this.endColor = endColor;
+    }
+}

MPChartLib/src/main/java/com/github/mikephil/charting/renderer/BarChartRenderer.java

@@ -19,6 +19,8 @@
 import com.github.mikephil.charting.utils.Transformer;
 import com.github.mikephil.charting.utils.Utils;
 import com.github.mikephil.charting.utils.ViewPortHandler;
+import android.graphics.LinearGradient;
+import com.github.mikephil.charting.model.GradientColor;
 
 import java.util.List;
 
@@ -163,6 +165,20 @@ protected void drawDataSet(Canvas c, IBarDataSet dataSet, int index) {
                 mRenderPaint.setColor(dataSet.getColor(j / 4));
             }
 
+            if (dataSet.getGradientColor() != null) {
+                GradientColor gradientColor = dataSet.getGradientColor();
+                 mRenderPaint.setShader(
+                    new LinearGradient(
+                        buffer.buffer[j],
+                        buffer.buffer[j + 3],
+                        buffer.buffer[j],
+                        buffer.buffer[j + 1],
+                        gradientColor.getStartColor(),
+                        gradientColor.getEndColor(),
+                        android.graphics.Shader.TileMode.MIRROR));
+            }
+
+
             c.drawRect(buffer.buffer[j], buffer.buffer[j + 1], buffer.buffer[j + 2],
                     buffer.buffer[j + 3], mRenderPaint);