fix bug

@@ -91,9 +91,12 @@
 - (void)setProgress:(float)progress animated:(BOOL)animated
 {
     BOOL isGrowing = progress > 0.f;
-    UIImageView * maskImageView =[[UIImageView alloc]initWithImage:[UIImage imageNamed:@"Mask"]];
-    self.progressBarView.maskView = maskImageView;
-    
+    UIImageView * maskImageView =[[UIImageView alloc]initWithFrame:CGRectMake(0, 0, CGRectGetWidth(self.progressBarView.frame), CGRectGetHeight(self.progressBarView.frame))];
+    CALayer *layer = [CALayer layer];
+    [layer setFrame:CGRectMake(0, 0, CGRectGetWidth(self.progressBarView.frame), CGRectGetHeight(self.progressBarView.frame))];
+     [layer setContents:(id)[UIImage imageNamed:@"Mask"].CGImage];
+//    self.progressBarView.maskView = maskImageView;
+    [self.progressBarView addSubview:maskImageView];
     
     CGFloat originX = -CGRectGetWidth(self.bounds)/2;
     CGPoint positionBegin = CGPointMake(originX+_progress * self.bounds.size.width, CGRectGetHeight(self.progressBarView.frame)/2);