added setRetainInstance()

mvp/src/main/java/com/hannesdorfmann/mosby/mvp/MvpActivity.java

@@ -35,6 +35,7 @@ public abstract class MvpActivity<V extends MvpView, P extends MvpPresenter<V>>
 
   protected ActivityMvpDelegate mvpDelegate;
   protected P presenter;
+  protected boolean retainInstance;
 
   @Override protected void onCreate(Bundle savedInstanceState) {
     super.onCreate(savedInstanceState);
@@ -128,7 +129,11 @@ public abstract class MvpActivity<V extends MvpView, P extends MvpPresenter<V>>
   }
 
   @Override public boolean isRetainingInstance() {
-    return false;
+    return retainInstance && isChangingConfigurations();
+  }
+
+  @Override public void setRetainInstance(boolean retainInstance) {
+    this.retainInstance = retainInstance;
   }
 
   @Override public Object onRetainNonMosbyCustomNonConfigurationInstance() {

mvp/src/main/java/com/hannesdorfmann/mosby/mvp/delegate/BaseMvpDelegateCallback.java

@@ -23,13 +23,14 @@
 /**
  * The MvpDelegate callback that will be called from  {@link
  * FragmentMvpDelegate} or {@link ViewGroupMvpDelegate}. This interface must be implemented by all
- * Fragment or android.view.View that you want to support mosbys mvp. Please note that Activties need a special callback {@link ActivityMvpDelegateCallback}
+ * Fragment or android.view.View that you want to support mosbys mvp. Please note that Activties
+ * need a special callback {@link ActivityMvpDelegateCallback}
  *
  * @param <V> The type of {@link MvpView}
  * @param <P> The type of {@link MvpPresenter}
  * @author Hannes Dorfmann
- * @since 1.1.0
  * @see ActivityMvpDelegateCallback
+ * @since 1.1.0
  */
 public interface BaseMvpDelegateCallback<V extends MvpView, P extends MvpPresenter<V>> {
 
@@ -71,4 +72,13 @@ public interface BaseMvpDelegateCallback<V extends MvpView, P extends MvpPresent
    * @return true if the view is retaining, hence the presenter should be retaining as well.
    */
   public boolean isRetainingInstance();
+
+  /**
+   * Mark this instance as retaining. This means that the feature of a retaining instance is
+   * enabled.
+   *
+   * @param retainingInstance true if retaining instance feature is enabled, otherwise false
+   * @see #isRetainingInstance()
+   */
+  public void setRetainInstance(boolean retainingInstance);
 }

mvp/src/main/java/com/hannesdorfmann/mosby/mvp/layout/MvpFrameLayout.java

@@ -109,4 +109,8 @@ public MvpFrameLayout(Context context, AttributeSet attrs, int defStyleAttr, int
   @Override public boolean isRetainingInstance() {
     return false;
   }
+
+  @Override public void setRetainInstance(boolean retainingInstance) {
+    throw new UnsupportedOperationException("Retainining Instance is not supported / implemented yet");
+  }
 }

mvp/src/main/java/com/hannesdorfmann/mosby/mvp/layout/MvpLinearLayout.java

@@ -109,4 +109,9 @@ public MvpLinearLayout(Context context, AttributeSet attrs, int defStyleAttr, in
   @Override public boolean isRetainingInstance() {
     return false;
   }
+
+
+  @Override public void setRetainInstance(boolean retainingInstance) {
+    throw new UnsupportedOperationException("Retainining Instance is not supported / implemented yet");
+  }
 }

mvp/src/main/java/com/hannesdorfmann/mosby/mvp/layout/MvpRelativeLayout.java

@@ -109,4 +109,9 @@ public MvpRelativeLayout(Context context, AttributeSet attrs, int defStyleAttr,
   @Override public boolean isRetainingInstance() {
     return false;
   }
+
+  @Override public void setRetainInstance(boolean retainingInstance) {
+    throw new UnsupportedOperationException(
+        "Retainining Instance is not supported / implemented yet");
+  }
 }