diff --git a/plugins/org.eclipse.actf.visualization.blind/src/org/eclipse/actf/visualization/blind/ui/actions/VisualizeAction.java b/plugins/org.eclipse.actf.visualization.blind/src/org/eclipse/actf/visualization/blind/ui/actions/VisualizeAction.java
index ef3dd41..8d96095 100644
--- a/plugins/org.eclipse.actf.visualization.blind/src/org/eclipse/actf/visualization/blind/ui/actions/VisualizeAction.java
+++ b/plugins/org.eclipse.actf.visualization.blind/src/org/eclipse/actf/visualization/blind/ui/actions/VisualizeAction.java
@@ -34,12 +34,12 @@
 		try {
 			IViewPart viewPart = this._window.getActivePage().showView(
 					IVisualizationView.ID_BLINDVIEW);
-			if (viewPart != null) {
+			if (viewPart instanceof IVisualizationView) {
 				((IVisualizationView) viewPart).doVisualize();
 			}
 
 		} catch (PartInitException pie) {
-			pie.printStackTrace();
+			//pie.printStackTrace();
 		}
 	}
 
diff --git a/plugins/org.eclipse.actf.visualization.lowvision/src/org/eclipse/actf/visualization/lowvision/ui/actions/SimulationAction.java b/plugins/org.eclipse.actf.visualization.lowvision/src/org/eclipse/actf/visualization/lowvision/ui/actions/SimulationAction.java
index 6b4eaa5..e259b1c 100644
--- a/plugins/org.eclipse.actf.visualization.lowvision/src/org/eclipse/actf/visualization/lowvision/ui/actions/SimulationAction.java
+++ b/plugins/org.eclipse.actf.visualization.lowvision/src/org/eclipse/actf/visualization/lowvision/ui/actions/SimulationAction.java
@@ -34,12 +34,12 @@
 		try {
 			IViewPart viewPart = this._window.getActivePage().showView(
 					IVisualizationView.ID_LOWVISIONVIEW);
-			if (viewPart != null) {
+			if (viewPart instanceof IVisualizationView) {
 				((IVisualizationView) viewPart).doVisualize();
 			}
 
 		} catch (PartInitException pie) {
-			pie.printStackTrace();
+			//pie.printStackTrace();
 		}
 	}