Bug 46:Fix issue with chart line if all y values are the same

app/src/main/java/com/yabu/livechartdemoapp/MainActivity.kt

@@ -43,7 +43,7 @@ class MainActivity : AppCompatActivity() {
             .setLiveChartStyle(chartStyle)
             .drawTouchOverlayAlways()
             .drawSmoothPath()
-            .setInitialTouchOverlayPosition(dataset.points[3].x)
+            .setInitialTouchOverlayPosition(dataset.points[3])
             .setOnTouchCallbackListener(object : LiveChart.OnTouchCallback {
                 @SuppressLint("SetTextI18n")
                 override fun onTouchCallback(point: DataPoint) {

livechart/src/main/java/com/yabu/livechart/model/Dataset.kt

@@ -2,21 +2,42 @@ package com.yabu.livechart.model
 
 data class Dataset(val points: MutableList<DataPoint>) {
 
+    private var upperBound= 0.0f
+    private var lowerBound= 0.0f
+
+    init {
+        val sortedPoint = points.sortedBy { point -> point.y }
+        upperBound = sortedPoint.lastOrNull()?.y ?: 0f
+        lowerBound = sortedPoint.firstOrNull { point -> point.x >= 0 }?.y ?: 0f
+        // If the upper and lower bound are the same the chart won't draw anything because
+        // `upperBound` and `lowerBound` are used or division and that can cause problems
+        if(hasData() && lowerBound==upperBound){
+            upperBound = increaseBound(upperBound)
+        }
+    }
+
     fun hasData(): Boolean {
         val sortedPoint = points.filter { point -> point.x > 0 }
         return sortedPoint.firstOrNull() != null
 
     }
 
     fun upperBound(): Float {
-        val sortedPoint = points.sortedBy { point -> point.y }
-        return sortedPoint.lastOrNull()?.y ?: 0f
+        return upperBound
     }
 
     fun lowerBound(): Float {
-        val sortedPoint = points.sortedBy { point -> point.y }
-            .filter { point -> point.x >= 0 }
-        return sortedPoint.firstOrNull()?.y ?: 0f
+        return lowerBound
+    }
+
+    private fun increaseBound(bound:Float): Float{
+        var step = bound
+        var increase = 0.1f
+        while (step < 1.0f) {
+            step *= 10.0f
+            increase *= 0.1f
+        }
+        return bound + increase
     }
 
     companion object {

livechart/src/main/java/com/yabu/livechart/view/LiveChartView.kt

@@ -542,7 +542,7 @@ open class LiveChartView(context: Context, attrs: AttributeSet?) : View(context,
 
             // Assign the lower bound of this chart,
             lowerBound = if (secondDataset.hasData()) {
-               min(dataset.lowerBound(), secondDataset.lowerBound())
+                min(dataset.lowerBound(), secondDataset.lowerBound())
             } else {
                 dataset.lowerBound()
             }