iPhone中自绘实现步骤

1. 继承@interface MyView : UIView {
2. 实现- (void)drawRect:(CGRect)rect
3. 调用addSubView把新生成的view加入进来显示
addSubView[window addSubview:viewController.view];
4.示例代码
- (void)drawRect:(CGRect)rect {
    // create the bitmap context
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = CGBitmapContextCreate(nil,100,100,8,400, colorSpace,kCGImageAlphaPremultipliedLast);
    CFRelease(colorSpace);
    
    //    create an arrow image
    // set the fill color
    CGColorRef fillColor = [[UIColor blackColor] CGColor];
    CGContextSetFillColor(context, CGColorGetComponents(fillColor));
    
    CGContextBeginPath(context);
    CGContextMoveToPoint(context, 8.0f, 13.0f);
    CGContextAddLineToPoint(context, 24.0f, 4.0f);
    CGContextAddLineToPoint(context, 24.0f, 22.0f);
    CGContextClosePath(context);
    CGContextFillPath(context);
    CGContextSelectFont ( context, "Arial", 10.f, kCGEncodingMacRoman );
    CGContextSetRGBFillColor ( context, 0.0f, 0.0f, 0.f, 1.f );
    CGContextSetShouldAntialias ( context, 0 );    
    CGContextShowText(context, "hh", 2);
    
    
    // convert the context into a CGImageRef
    CGImageRef image = CGBitmapContextCreateImage(context);
    CGContextRelease(context);
    
    UIImage* image2 = [UIImage imageWithCGImage:image];
    [image2 drawInRect:CGRectMake(0, 0, 120, 160)];
    
    NSString* myStr = @"中文";
    UIFont* font = [UIFont systemFontOfSize:12.0];
    [myStr drawInRect: CGRectMake(160, 240, 100, 130) withFont:font lineBreakMode:UILineBreakModeWordWrap alignment:UITextAlignmentCenter];

    

渐变

 CGContextRef currentContext = UIGraphicsGetCurrentContext();
    
    CGGradientRef glossGradient;
    CGColorSpaceRef rgbColorspace;
    size_t num_locations = 3;
    CGFloat locations[3] = { 0.0, 0.5, 1.0 };
    CGFloat components[12] = { 208/255.0, 208/255.0, 208/255.0, 0.95,  // Start color
        208/255.0, 208/255.0, 208/255.0, 0.60,
        208/255.0, 208/255.0, 208/255.0, 0.10 }; // End color
    
    rgbColorspace = CGColorSpaceCreateDeviceRGB();
    glossGradient = CGGradientCreateWithColorComponents(rgbColorspace, components, locations, num_locations);
    CGContextFillRect(currentContext, self.frame);
    CGRect currentBounds = self.bounds;
    CGPoint topCenter = CGPointMake(CGRectGetMidX(currentBounds), 0.0f);
    CGPoint midCenter = CGPointMake(CGRectGetMidX(currentBounds), CGRectGetMaxY(currentBounds));
    CGContextDrawLinearGradient(currentContext, glossGradient, topCenter, midCenter, 0);
    
    CGGradientRelease(glossGradient);
    CGColorSpaceRelease(rgbColorspace);

}