ios 实时刷新屏幕

    index=0;
//    timer = [NSTimer scheduledTimerWithTimeInterval:0.1 target:layer selector:@selector(setNeedsDisplay) userInfo:nil repeats:YES];
    [arrM removeAllObjects];
    Link = [CADisplayLink displayLinkWithTarget:layer selector:@selector(setNeedsDisplay)];
    [Link addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];