Utils restructure

Author: hannesa2

MPChartLib/src/main/java/com/github/mikephil/charting/charts/BarLineChartBase.java

@@ -36,6 +36,8 @@
 import com.github.mikephil.charting.utils.Transformer;
 import com.github.mikephil.charting.utils.Utils;
 
+import androidx.annotation.NonNull;
+
 /**
  * Base-class of LineChart, BarChart, ScatterChart and CandleStickChart.
  *
@@ -191,7 +193,7 @@ protected void init() {
     private long drawCycles = 0;
 
     @Override
-    protected void onDraw(Canvas canvas) {
+    protected void onDraw(@NonNull Canvas canvas) {
         super.onDraw(canvas);
 
         if (mData == null)
@@ -465,7 +467,7 @@ protected void calculateLegendOffsets(RectF offsets) {
         }
     }
 
-    private RectF mOffsetsBuffer = new RectF();
+    private final RectF mOffsetsBuffer = new RectF();
 
     @Override
     public void calculateOffsets() {

MPChartLib/src/main/java/com/github/mikephil/charting/charts/Chart.java

@@ -48,6 +48,8 @@
 import java.util.Collections;
 import java.util.List;
 
+import androidx.annotation.NonNull;
+
 /**
  * Baseclass of all Chart-Views.
  *
@@ -375,7 +377,7 @@ protected void setupDefaultFormatter(float min, float max) {
 	private boolean mOffsetsCalculated = false;
 
 	@Override
-	protected void onDraw(Canvas canvas) {
+	protected void onDraw(@NonNull Canvas canvas) {
 		// super.onDraw(canvas);
 
 		if (mData == null) {