//可以不被电池栏挡住
+ (UILabel *)alertLabel
{
UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(0, 20.f, 320.f, 0.f)];
label.backgroundColor = [UIColor colorWithRed:240.f/255.f green:224.f/255.f blue:149.f/255.f alpha:1.0];
label.textAlignment = NSTextAlignmentCenter;
label.font = [UIFont systemFontOfSize:14];
[[self alertWindow] addSubview:label];
return label;
}
+ (void)alertHeadMessage:(NSString *)message
{
CGFloat alertHeight = 30.f;
__weak UIWindow *window = [self alertWindow];
__weak UILabel *label = [self alertLabel];
label.text = message;
label.frame = CGRectMake(0, -30.f, window.frame.size.width, alertHeight);
[UIView animateWithDuration:0.5f animations:^{
label.frame = CGRectMake(0, 0.f, window.frame.size.width, alertHeight);
} completion:^(BOOL finished) {
[UIView animateWithDuration:2.5f animations:^{
label.frame = CGRectMake(0, 0.f, window.frame.size.width, alertHeight + 2);
} completion:^(BOOL finished) {
[UIView animateWithDuration:0.4 animations:^{
label.frame = CGRectMake(0, -30.f, window.frame.size.width, alertHeight);
} completion:^(BOOL finished) {
[label removeFromSuperview];
}];
}];
}];
[window makeKeyAndVisible];
}
原文：http://www.cnblogs.com/ldc529/p/3874842.html