CGContextStrokePath和CGContextFillRect的问题

Question

我在绘制下图时遇到了问题。

首先，我使用CGContextMoveToPoint，CGContextAddLineToPoint和CGContextStrokePath绘制网格线。然后，我用CGContextFillRect绘制图条。

为什么在图表上方绘制线条？

这是请求的代码。有点复杂，因为我想支持几个图表配置。

- (void)drawRect:(CGRect)rect
 {
        [super drawRect:rect];

        CGContextRef context = UIGraphicsGetCurrentContext();
        CGRect rectHistView = self.bounds;
        CGFloat red, green, blue, alpha;
        NSUInteger valueIndex = 0;
        CGFloat histX, histY, histHeight;
        CGFloat gridX, gridY, gridHeight;
        NSString *txt;
        CGSize txtSize;

        // Initialize font color and set font drawing mode
        CGContextSetTextDrawingMode(context, kCGTextFill);
        NSDictionary *attrDictAxisValues = @{NSFontAttributeName:[UIFont systemFontOfSize:cfgAxisValuesFontSize],
                                             NSForegroundColorAttributeName:cfgColorAxisValues};
        NSDictionary *attrDictBarValues = @{NSFontAttributeName:[UIFont systemFontOfSize:cfgAxisValuesFontSize],
                                            NSForegroundColorAttributeName:cfgColorBarValues};

        // Calculate bar width and gap offset
        CGFloat histWidth         = rectHistView.size.width / [histValues count];
        CGFloat histMaxViewHeight = bCfgShowXAxisValues ? rectHistView.size.height - cfgAxisValuesFontSize : rectHistView.size.height;
        CGFloat gapOffset         = histWidth * cfgBarGapPercentage / 2;

        //--------------------------------------------------------
        // Draw y-grid
        //--------------------------------------------------------
        if (bCfgShowYGrid) {
            CGContextSetStrokeColorWithColor(context, HIST_CFG_UICOLOR_GRID.CGColor);
            CGContextSetLineWidth(context, HIST_CFG_LINE_WIDTH_GRID);

            gridHeight = bCfgShowBarValues ? histMaxViewHeight - cfgAxisValuesFontSize - HIST_CFG_FONT_GAP: histMaxViewHeight;

            for (int y = 1; y <= histValueMax; y++) {
                gridY = bCfgShowXAxisValues ? rectHistView.origin.y + rectHistView.size.height - (gridHeight * y / histValueMax) - cfgAxisValuesFontSize
                                            : rectHistView.origin.y + rectHistView.size.height - (gridHeight * y / histValueMax);

                CGContextMoveToPoint(context, rectHistView.origin.x, gridY);
                CGContextAddLineToPoint(context, rectHistView.origin.x + rectHistView.size.width, gridY);
            }
            CGContextStrokePath(context);
        }

        //--------------------------------------------------------
        // Draw histogram
        //--------------------------------------------------------
        for (NSString *val in histValues) {

            histX      = rectHistView.origin.x + (valueIndex * histWidth);
            histHeight = bCfgShowBarValues   ? (histMaxViewHeight - cfgAxisValuesFontSize - HIST_CFG_FONT_GAP) * [val floatValue] / histValueMax
                                             : histMaxViewHeight * [val floatValue] / histValueMax;
            histY      = bCfgShowXAxisValues ? rectHistView.origin.y + rectHistView.size.height - histHeight - cfgAxisValuesFontSize
                                             : rectHistView.origin.y + rectHistView.size.height - histHeight;

            // draw x-grid
            if (bCfgShowXGrid) {

                gridX      = rectHistView.origin.x + ((valueIndex+1) * histWidth);
                gridY      = bCfgShowXAxisValues ? rectHistView.origin.y + rectHistView.size.height - cfgAxisValuesFontSize
                                                 : rectHistView.origin.y + rectHistView.size.height;

                CGContextSetStrokeColorWithColor(context, HIST_CFG_UICOLOR_GRID.CGColor);
                CGContextSetLineWidth(context, HIST_CFG_LINE_WIDTH_GRID);

                CGContextMoveToPoint(context, gridX, bCfgShowBarValues ? rectHistView.origin.y + cfgAxisValuesFontSize + HIST_CFG_FONT_GAP
                                                                       : rectHistView.origin.y);
                CGContextAddLineToPoint(context, gridX, gridY);
                CGContextStrokePath(context);
            }

            // draw x-axis values
            if (bCfgShowXAxisValues) {
                txt = [NSString stringWithFormat:@"%lu", (unsigned long)valueIndex];
                txtSize = [txt sizeWithAttributes:attrDictAxisValues];

                [txt drawAtPoint:CGPointMake(rectHistView.origin.x + (valueIndex * histWidth) + (histWidth / 2.0f - txtSize.width / 2.0f),
                                             rectHistView.origin.y + rectHistView.size.height - cfgAxisValuesFontSize)
                     withAttributes:attrDictAxisValues];
            }

            // get color from array
            UIColor *color = [histColor objectAtIndex:valueIndex];
            [color getRed:&red green:&green blue:&blue alpha:&alpha];

            // draw histogram bar
            CGContextSetRGBFillColor(context, red, green, blue, alpha);
            CGContextFillRect(context, CGRectMake(histX+gapOffset, histY, histWidth-(2*gapOffset), histHeight));

            // draw histogram bar values
            if (bCfgShowBarValues) {
                if (bCfgShowZeroBarValues || [val intValue] > 0) {          // skip zero values if configured
                    txt = [NSString stringWithFormat:@"%d", [val intValue]];
                    CGSize txtSize = [txt sizeWithAttributes:attrDictBarValues];

                    [txt drawAtPoint:CGPointMake(rectHistView.origin.x + (valueIndex * histWidth) + (histWidth / 2.0f - txtSize.width / 2.0f),
                                             histY - cfgAxisValuesFontSize - HIST_CFG_FONT_GAP)
                        withAttributes:attrDictBarValues];
                }
            }

            valueIndex++;
        }

        //--------------------------------------------------------
        // Draw diagram axis
        //--------------------------------------------------------
        CGContextSetStrokeColorWithColor(context, HIST_CFG_UICOLOR_AXIS.CGColor);
        CGContextSetLineWidth(context, HIST_CFG_LINE_WIDTH_AXIS);

        // draw y-axis
        if (bCfgShowYAxis) {
            CGContextMoveToPoint(context, rectHistView.origin.x,
                                 bCfgShowBarValues ? rectHistView.origin.y + cfgAxisValuesFontSize + HIST_CFG_FONT_GAP: rectHistView.origin.y);
            CGContextAddLineToPoint(context, rectHistView.origin.x, rectHistView.origin.y + histMaxViewHeight);
            CGContextStrokePath(context);
        }

        // draw x-axis
        if (bCfgShowXAxis) {
            histY = bCfgShowXAxisValues ? rectHistView.origin.y + rectHistView.size.height - cfgAxisValuesFontSize
                                        : rectHistView.origin.y + rectHistView.size.height;

            CGContextMoveToPoint(context, rectHistView.origin.x, histY);
            CGContextAddLineToPoint(context, rectHistView.origin.x + rectHistView.size.width, histY);
            CGContextStrokePath(context);
        }
    }