Make getViewModel as NonNull

Author: Daniel Novak

library/src/main/java/eu/inloop/viewmodel/ViewModelHelper.java

@@ -152,8 +152,18 @@ public void onStart() {
     }
 
 
-    @Nullable
+    /**
+     * Returns the current ViewModel instance associated with the Fragment or Activity.
+     * Throws an {@link IllegalStateException} in case the ViewModel is null. This can happen
+     * if you call this method too soon - before {@link Activity#onCreate(Bundle)} or {@link Fragment#onCreate(Bundle)}
+     * or this {@link ViewModelHelper} is not properly setup.
+     * @return {@link R}
+     */
+    @NonNull
     public R getViewModel() {
+        if (null == mViewModel) {
+            throw new IllegalStateException("ViewModel is not ready. Are you calling this method before Activity/Fragment onCreate?"); //NON-NLS
+        }
         return mViewModel;
     }
 

library/src/main/java/eu/inloop/viewmodel/base/ViewModelBaseActivity.java

@@ -53,8 +53,11 @@ public void onDestroy() {
         super.onDestroy();
     }
 
+    /**
+     * @see ViewModelHelper#getViewModel()
+     */
     @SuppressWarnings("unused")
-    @Nullable
+    @NonNull
     public R getViewModel() {
         return mViewModeHelper.getViewModel();
     }

library/src/main/java/eu/inloop/viewmodel/base/ViewModelBaseFragment.java

@@ -61,7 +61,10 @@ public void onDestroy() {
         super.onDestroy();
     }
 
-    @Nullable
+    /**
+     * @see ViewModelHelper#getViewModel()
+     */
+    @NonNull
     @SuppressWarnings("unused")
     public R getViewModel() {
        return mViewModeHelper.getViewModel();