UITextView自动滚动的解决方案

思路：UIView加载完成3后，用NSTimer结合setContentOffset将UITextView向下滚动1像素。在滚动到底部的时候停止NSTimer。每当手动滚动UITextView前销毁NSTimer，滚动后重新创建NSTimer。

NSTimer *timer;
- (void)viewDidLoad {
    [self performSelector:@selector(resetText) withObject:nil afterDelay:3.0f];
}
 
- (void)resetText { 
    [timer invalidate];
    timer = nil;
    timer = [NSTimer scheduledTimerWithTimeInterval: 0.06
                                             target: self
                                           selector:@selector(onTick:)
                                           userInfo: nil repeats:YES];
}
 
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView {
    [timer invalidate];
    timer = nil;
    NSLog(@"scrollViewWillBeginDragging");
    [self performSelector:@selector(resetText) withObject:nil afterDelay:3.0f];
}
- (void) onTick:(NSTimer*)theTimer {
    CGPoint pt = [textView contentOffset];
    CGFloat n = pt.y + 1;
    [textView setContentOffset:CGPointMake(pt.x, n)];   
    if (n> (textView.contentSize.height-textView.bounds.size.height)) {
        [theTimer invalidate];
        theTimer = nil;
        [timer invalidate];
        timer = nil;
    }
}