Visualize volume over time

app/src/main/java/protect/babymonitor/VolumeView.java

@@ -3,45 +3,66 @@ package protect.babymonitor;
 import android.content.Context;
 import android.graphics.Canvas;
 import android.graphics.Color;
+import android.graphics.Paint;
 import android.support.annotation.Nullable;
 import android.util.AttributeSet;
+import android.util.Log;
 import android.view.View;
 
+import java.util.LinkedList;
+
 public class VolumeView extends View {
+    private static final int MAX_HISTORY = 10_000;
     private double volume = 0;
     private double maxVolume = 0;
+    private Paint paint = new Paint();
+    private LinkedList<Double> volumeHistory = new LinkedList<>();
 
     public VolumeView(Context context) {
         super(context);
+        init();
     }
 
     public VolumeView(Context context, @Nullable AttributeSet attrs) {
         super(context, attrs);
+        init();
     }
 
     public VolumeView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
         super(context, attrs, defStyleAttr);
+        init();
+    }
+
+    private void init() {
+        paint.setColor(Color.rgb(255, 127, 0));
     }
 
     public void onAudioData(byte[] data) {
         double sum = 0;
         for (int i = 0; i < data.length; i++) {
-            double rel = Math.abs(data[i]) / (double)32767f;
+            double rel = data[i] / (double)32767f;
             sum+=Math.pow(rel, 4);
         }
         volume = sum/data.length;
         if (volume > maxVolume) {
             maxVolume = volume;
         }
+        volumeHistory.addLast(volume);
+        while (volumeHistory.size() > MAX_HISTORY) {
+            volumeHistory.removeFirst();
+        }
         invalidate();
     }
 
     @Override
     protected void onDraw(Canvas canvas) {
+        int height = canvas.getHeight();
+        int width = canvas.getWidth();
+        Log.d("VOLUME_VIEW", "height: " + height +" width: "+ width);
         double relativeBrightness = 0;
         if (maxVolume > 0) {
-            relativeBrightness = volume / (float) maxVolume;
+            double normalizedVolume = volume / (float) maxVolume;
-            relativeBrightness = Math.max(0.3, relativeBrightness);
+            relativeBrightness = Math.max(0.3, normalizedVolume);
         }
         int blue;
         int rest;
@@ -54,5 +75,25 @@ public class VolumeView extends View {
         }
         int rgb = Color.rgb(rest, rest, blue);
         canvas.drawColor(rgb);
+        if (maxVolume > 0) {
+            double margins = height * 0.1;
+            double graphHeight = height - 2*margins;
+            int yPrev = (int) margins;
+            int leftMost = Math.max(0, volumeHistory.size() - width);
+            for (int i = leftMost; i < volumeHistory.size() && i - leftMost < width; i++) {
+                int xNext = i - leftMost;
+                int yNext = (int) (margins + graphHeight - volumeHistory.get(i) / maxVolume * (graphHeight));
+                int xPrev;
+                if (i == leftMost) {
+                    xPrev = xNext;
+                } else {
+                    xPrev = xNext - 1;
+                }
+                canvas.drawLine(xPrev, yPrev, xNext, yNext, paint);
+                yPrev = yNext;
+
+            }
+        }
+
     }
 }