[iOS] Use lock to add mutex for _backgroundColor property usage.

Author: qianyuan.wqy

ios/sdk/WeexSDK/Sources/Display/WXComponent+Display.m

@@ -349,13 +349,15 @@ - (void)_drawBorderWithContext:(CGContextRef)context size:(CGSize)size
 
     CGContextSetAlpha(context, _opacity);
     // fill background color
-    if (_backgroundColor && CGColorGetAlpha(_backgroundColor.CGColor) > 0) {
-        CGContextSetFillColorWithColor(context, _backgroundColor.CGColor);
-        UIBezierPath *bezierPath = [UIBezierPath wx_bezierPathWithRoundedRect:rect topLeft:topLeft topRight:topRight bottomLeft:bottomLeft bottomRight:bottomRight];
-        [bezierPath fill];
-        WXPerformBlockOnMainThread(^{
-            _view.backgroundColor = UIColor.clearColor;
-        });
+    @synchronized (self) {
+        if (_backgroundColor && CGColorGetAlpha(_backgroundColor.CGColor) > 0) {
+            CGContextSetFillColorWithColor(context, _backgroundColor.CGColor);
+            UIBezierPath *bezierPath = [UIBezierPath wx_bezierPathWithRoundedRect:rect topLeft:topLeft topRight:topRight bottomLeft:bottomLeft bottomRight:bottomRight];
+            [bezierPath fill];
+            WXPerformBlockOnMainThread(^{
+                _view.backgroundColor = UIColor.clearColor;
+            });
+        }
     }
     // Top
     if (_borderTopWidth > 0) {

ios/sdk/WeexSDK/Sources/Model/WXComponent.mm

@@ -857,7 +857,9 @@ - (void)setGradientLayer
             UIColor * endColor = (UIColor*)linearGradient[@"endColor"];
             CAGradientLayer * gradientLayer = [WXUtility gradientLayerFromColors:@[startColor, endColor] locations:nil frame:strongSelf.view.bounds gradientType:(WXGradientType)[linearGradient[@"gradientType"] integerValue]];
             if (gradientLayer) {
-                _backgroundColor = [UIColor colorWithPatternImage:[strongSelf imageFromLayer:gradientLayer]];
+                @synchronized (strongSelf) {
+                    _backgroundColor = [UIColor colorWithPatternImage:[strongSelf imageFromLayer:gradientLayer]];
+                }
                 strongSelf.view.backgroundColor = _backgroundColor;
                 [strongSelf setNeedsDisplay];
             }

ios/sdk/WeexSDK/Sources/View/WXComponent+ViewManagement.mm

@@ -193,7 +193,9 @@ - (void)_transitionUpdateViewProperty:(NSDictionary *)styles
 {
     WX_CHECK_COMPONENT_TYPE(self.componentType)
     if (styles[@"backgroundColor"]) {
-        _backgroundColor = [WXConvert UIColor:styles[@"backgroundColor"]];
+        @synchronized (self) {
+            _backgroundColor = [WXConvert UIColor:styles[@"backgroundColor"]];
+        }
     }
     if (styles[@"opacity"]) {
         _opacity = [WXConvert CGFloat:styles[@"opacity"]];
@@ -211,7 +213,9 @@ - (void)_updateViewStyles:(NSDictionary *)styles
     }
 
     if (styles[@"backgroundColor"]) {
-        _backgroundColor = [WXConvert UIColor:styles[@"backgroundColor"]];
+        @synchronized (self) {
+            _backgroundColor = [WXConvert UIColor:styles[@"backgroundColor"]];
+        }
         [self setNeedsDisplay];
     }
 
@@ -307,7 +311,9 @@ - (void)resetBorder:(NSArray *)styles
 - (void)_resetStyles:(NSArray *)styles
 {
     if (styles && [styles containsObject:@"backgroundColor"]) {
-        _backgroundColor = [UIColor clearColor];
+        @synchronized (self) {
+            _backgroundColor = [UIColor clearColor];
+        }
         [self setNeedsDisplay];
     }
     if (styles && [styles containsObject:@"boxShadow"]) {