Fix #110

This addresses the issue when multiple BlurViews could trigger recursive redraw of each other

library/src/main/java/eightbitlab/com/blurview/BlockingBlurController.java

@@ -5,13 +5,14 @@
 import android.graphics.Color;
 import android.graphics.Paint;
 import android.graphics.drawable.Drawable;
-import androidx.annotation.ColorInt;
-import androidx.annotation.NonNull;
-import androidx.annotation.Nullable;
 import android.view.View;
 import android.view.ViewGroup;
 import android.view.ViewTreeObserver;
 
+import androidx.annotation.ColorInt;
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
 /**
  * Blur Controller that handles all blur logic for the attached View.
  * It honors View size changes, View animation and Visibility changes.
@@ -32,7 +33,7 @@ final class BlockingBlurController implements BlurController {
     private float blurRadius = DEFAULT_BLUR_RADIUS;
 
     private BlurAlgorithm blurAlgorithm;
-    private Canvas internalCanvas;
+    private BlurViewCanvas internalCanvas;
     private Bitmap internalBitmap;
 
     @SuppressWarnings("WeakerAccess")
@@ -93,7 +94,7 @@ void init(int measuredWidth, int measuredHeight) {
 
         blurView.setWillNotDraw(false);
         allocateBitmap(measuredWidth, measuredHeight);
-        internalCanvas = new Canvas(internalBitmap);
+        internalCanvas = new BlurViewCanvas(internalBitmap);
         initialized = true;
 
         if (hasFixedTransformationMatrix) {
@@ -153,8 +154,10 @@ public boolean draw(Canvas canvas) {
         if (!blurEnabled || !initialized) {
             return true;
         }
-        // Not blurring own children
-        if (canvas == internalCanvas) {
+        // Not blurring itself or other BlurViews to not cause recursive draw calls
+        // Related: https://github.com/Dimezis/BlurView/issues/110
+        //          https://github.com/Dimezis/BlurView/issues/110
+        if (canvas instanceof BlurViewCanvas) {
             return false;
         }
 

library/src/main/java/eightbitlab/com/blurview/BlurViewCanvas.java

@@ -0,0 +1,14 @@
+package eightbitlab.com.blurview;
+
+import android.graphics.Bitmap;
+import android.graphics.Canvas;
+
+import androidx.annotation.NonNull;
+
+// Servers purely as a marker of a Canvas used in BlurView
+// to skip drawing itself and other BlurViews on the View hierarchy snapshot
+public class BlurViewCanvas extends Canvas {
+    public BlurViewCanvas(@NonNull Bitmap bitmap) {
+        super(bitmap);
+    }
+}