在iOS中实现类似安卓自动消失提示框

类方法:

+ (void)showMessage:(NSString *)message {
    // 获取window
    UIWindow *window = [UIApplication sharedApplication].keyWindow;
    UIView *showView = [[UIView alloc] init];
    showView.backgroundColor = [UIColor blackColor];
    showView.frame = CGRectMake(1, 1, 1, 1);
    showView.alpha = 1.0f;
    showView.layer.cornerRadius = 5.0f;
    showView.layer.masksToBounds = YES;
    [window addSubview:showView];

    UILabel *label = [[UILabel alloc] init];
    UIFont *font = [UIFont systemFontOfSize:15];
    CGRect labelRect = [message boundingRectWithSize:CGSizeMake(290, CGFLOAT_MAX) options:NSStringDrawingUsesLineFragmentOrigin attributes:@{NSFontAttributeName: font} context:nil];
    label.frame = CGRectMake(10, 5, CGRectGetWidth(labelRect), CGRectGetHeight(labelRect));
    label.text = message;
    label.textColor = [UIColor whiteColor];
    label.textAlignment = NSTextAlignmentCenter;
    label.backgroundColor = [UIColor clearColor];
    [showView addSubview:label];
    showView.frame = CGRectMake((SCREEN_WIDTH - CGRectGetWidth(labelRect) - 20)/2, SCREEN_HEIGHT - 100, CGRectGetWidth(labelRect)+20, CGRectGetHeight(labelRect)+10);
    [UIView animateWithDuration:1.5 animations:^{
        showView.alpha = 0;
    } completion:^(BOOL finished) {
        [showView removeFromSuperview];
    }];

}