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下面是我自定义视图的drawRect，它画了一个棋盘，棋盘有19*19的线，上下左右各有一个字符，左右各1-19，也是9个点：

- (void)drawRect:(CGRect)rect
{
    // Get the drawing context
    CGContextRef context = UIGraphicsGetCurrentContext ();

    CGContextSaveGState(context);

    // Draw the board background
    UIImage *bk = [UIImage imageNamed:@"board_bg_011.png"];

    CGColorRef shadowColor = CreateDeviceRGBColor(0.5, 0.5, 0.5, 1);
    CGContextSetShadowWithColor(context, CGSizeMake(2, 2), 10, shadowColor);
    [bk drawInRect:CGRectMake(TEXT_AREA_OFFSET, TEXT_AREA_OFFSET, self.bounds.size.width - TEXT_AREA_OFFSET * 2, self.bounds.size.height - TEXT_AREA_OFFSET * 2)];

    CGColorRelease(shadowColor);
    CGContextRestoreGState(context);

    // Draw board edage square
    UIBezierPath *path = [UIBezierPath bezierPathWithRect:tableRect];
    path.lineWidth = 2.0;
    [path stroke];

    // Draw board lines
    UIBezierPath *line = [UIBezierPath bezierPath];
    line.lineWidth = 1.0;
    for (int i = 1; i <= 17; i ++) {
        float x = tableRect.origin.x + i * qiziSize;
        [line moveToPoint:CGPointMake(x, tableRect.origin.y)];
        [line addLineToPoint:CGPointMake(x, tableRect.origin.y + tableRect.size.height)];
        [line stroke];

        float y = tableRect.origin.y + i * qiziSize;
        [line moveToPoint:CGPointMake(tableRect.origin.x, y)];
        [line addLineToPoint:CGPointMake(tableRect.origin.x + tableRect.size.width, y)];
        [line stroke];
    }

    // Draw 9 dots
    CGContextSaveGState(context);

    CGRect dotRect = CGRectMake(0, 0, 6, 6);
    CGContextTranslateCTM(context, tableRect.origin.x + qiziSize * 3 - 3, tableRect.origin.y + qiziSize * 3 - 3);
    UIBezierPath *dot = [UIBezierPath bezierPathWithOvalInRect:dotRect];
    [dot fill];

    CGContextTranslateCTM(context, qiziSize * 6, 0);
    [dot fill];

    CGContextTranslateCTM(context, qiziSize * 6, 0);
    [dot fill];

    CGContextTranslateCTM(context, - qiziSize * 12, qiziSize * 6);
    [dot fill];

    CGContextTranslateCTM(context, qiziSize * 6, 0);
    [dot fill];

    CGContextTranslateCTM(context, qiziSize * 6, 0);
    [dot fill];

    CGContextTranslateCTM(context, - qiziSize * 12, qiziSize * 6);
    [dot fill];

    CGContextTranslateCTM(context, qiziSize * 6, 0);
    [dot fill];

    CGContextTranslateCTM(context, qiziSize * 6, 0);
    [dot fill];

    CGContextRestoreGState(context);

    CGContextSaveGState(context);

    UIFont *font = [UIFont fontWithName:@"Helvetica" size:12];
    int fontHeight = [@"1" sizeWithFont:font].height;
    UIColor *textColor = [UIColor grayColor];
    [textColor setFill];
    [textColor setStroke];

    for (int i = 1; i <= 19; i ++) {
        // Top text
        NSString *str = [NSString stringWithFormat:@"%c", ((i < 9)?i:(i+1)) + 'A' - 1];
        CGRect textRect = CGRectMake(tableRect.origin.x + qiziSize * (i - 1) - qiziSize / 2, 0, qiziSize, TEXT_AREA_OFFSET);
        [str drawInRect:textRect withFont:font lineBreakMode:UILineBreakModeClip alignment:UITextAlignmentCenter];

        // Bottom text
        textRect.origin.y = self.bounds.size.height - TEXT_AREA_OFFSET + 2;
        [str drawInRect:textRect withFont:font lineBreakMode:UILineBreakModeClip alignment:UITextAlignmentCenter];

        // Left text
        str = [NSString stringWithFormat:@"%i", i];
        textRect = CGRectMake(0, tableRect.origin.y + qiziSize * (i - 1) - fontHeight / 2, TEXT_AREA_OFFSET - 2, fontHeight);
        [str drawInRect:textRect withFont:font lineBreakMode:UILineBreakModeClip alignment:UITextAlignmentRight];

        // Right text
        textRect.origin.x = self.bounds.size.width - TEXT_AREA_OFFSET + 2;
        [str drawInRect:textRect withFont:font lineBreakMode:UILineBreakModeClip alignment:UITextAlignmentLeft];
    }

    CGContextRestoreGState(context);
}

在 iPad3 上运行，此方法耗时 1 秒以上。关于如何优化它有什么建议吗？

提前致谢。

4

1 回答 1

2

我认为这是您之前关于旋转性能不佳的问题的后续。

创建和绘制（和缩放）图像和字体非常昂贵。在工具中使用时间分析器将突出显示代码中最昂贵的区域，但这些是最有可能的候选者。

您应该考虑将您的视图分解为 UIImageView 和 UILabel 实例，它们将缓存它们的后备存储并且不需要重新绘制，只需重新定位。但是，在您分析代码并发现性能瓶颈之前，您不应该做任何事情。

于 2012-10-07T15:51:48.300 回答