iPhone 4 可以muchCoreGraphics 处理速度较慢。
针对您的情况的一种可能的想法。当用户滚动时,不要绘制全分辨率,而是绘制与 CoreGraphics 相关的内容半分辨率上下文。然后将该上下文作为位图并将其放大到全分辨率。这仅适用于 iPhone4,您将失去更高分辨率的质量,但仅限于用户滚动时。
这是我为在不同设备之间进行测试而编写的一些代码。
我在全屏显示视图时的结果。
- 3G, 9 FPS
- 3GS, 16 FPS
- i4, 5 FPS(无赖)
CoreGraphicsTestView.h
#import <UIKit/UIKit.h>
@interface CoreGraphicsTestView : UIView
{
int displayCounter;
float displayInterval;
char fps[50];
}
@end
CoreGraphicsTestView.m
#import "CoreGraphicsTestView.h"
#define RNDN(s, e) ((((CGFloat)rand() / (CGFloat)INT_MAX) * ((e)-(s)) + (s)))
#define RNDX(s, e, r) (RNDN((s), (e)) * (r).size.width)
#define RNDY(s, e, r) (RNDN((s), (e)) * (r).size.height)
#define RNDR(r) (CGRectMake(RNDX(0,0.50,(r)),RNDY(0,0.50,(r)),RNDX(0.50,1.0,(r)),RNDY(0.50,1.0,(r))))
@implementation CoreGraphicsTestView
- (id)initWithFrame:(CGRect)frame
{
if ((self = [super initWithFrame:frame]))
{
self.backgroundColor = [UIColor blackColor];
srand(time(NULL));
fps[0] = '\0';
}
return self;
}
- (void)updateDisplayCounter:(CGContextRef)c rect:(CGRect)rect
{
displayCounter++;
float now = (float)clock() / (float)CLOCKS_PER_SEC;
if (now - displayInterval > 1)
{
sprintf(fps, "%0.0f", displayCounter / (now - displayInterval));
printf("%s\n", fps);
displayInterval = now;
displayCounter = 0;
}
CGContextTranslateCTM(c, 5, 40);
CGContextScaleCTM(c, 1.0, -1.0);
CGContextSetFillColorWithColor(c, [UIColor whiteColor].CGColor);
CGContextSelectFont(c, "Arial", 18, kCGEncodingMacRoman);
CGContextShowTextAtPoint(c, 0, 0, fps, strlen(fps));
}
- (void)setRandomColor:(CGContextRef)c
{
CGFloat components[4] = {1,RNDN(0, 1),RNDN(0, 1),RNDN(0, 1)};
CGContextSetFillColor(c, components);
}
- (void)drawRect:(CGRect)rect
{
CGContextRef c = UIGraphicsGetCurrentContext();
for (int i=0;i<5;i++)
{
[self setRandomColor:c];
CGContextFillRect(c, RNDR(rect));
[self setRandomColor:c];
CGContextFillEllipseInRect(c, RNDR(rect));
}
[self updateDisplayCounter:c rect:rect];
[self performSelector:@selector(setNeedsDisplay) withObject:nil afterDelay:0.0];
}
@end