CameraListeners now must be non null

cameraview/src/main/java/com/otaliastudios/cameraview/CameraView.java

@@ -1189,11 +1189,9 @@ public class CameraView extends FrameLayout implements LifecycleObserver {
      *
      * @param cameraListener a listener for events.
      */
-    public void addCameraListener(@Nullable CameraListener cameraListener) {
-        if (cameraListener != null) {
+    public void addCameraListener(@NonNull CameraListener cameraListener) {
         mListeners.add(cameraListener);
     }
-    }
 
 
     /**
@@ -1201,11 +1199,9 @@ public class CameraView extends FrameLayout implements LifecycleObserver {
      *
      * @param cameraListener a listener for events.
      */
-    public void removeCameraListener(@Nullable CameraListener cameraListener) {
-        if (cameraListener != null) {
+    public void removeCameraListener(@NonNull CameraListener cameraListener) {
         mListeners.remove(cameraListener);
     }
-    }
 
 
     /**

docs/_posts/2018-12-20-preview-size.md

@@ -86,3 +86,4 @@ After the preview size is determined, if it has changed since list time, the `Ca
 another call to `onMeasure` so the `WRAP_CONTENT` magic can take place.
 
 To understand how SizeSelectors work and the available utilities, please read the [Capture Size](capture-size.html) document.
+