就是通過uitextfield的leftview來實現(xiàn)的，同時要設置leftviewmode。
如果設置左右邊距，需要再加上rightView功能
- (void)setTextFieldLeftPadding:(UITextField *)textField forWidth:(CGFloat)leftWidth
{
CGRect frame = textField.frame;
frame.size.width = leftWidth;
UIView *leftview = [[UIView alloc] initWithFrame:frame];
textField.leftViewMode = UITextFieldViewModeAlways;
textField.leftView = left view;
}
