警告對話框UIAlertView和等待提示器UIActivityIndicatorView:
1.UIAlertView簡單一點就是彈框
2.就是所謂的菊花轉圈圈

聲明：注意@interface ViewController : UIViewController這個裡面多了一個UIAlertViewDelegate代理<喎?/kf/ware/vc/" target="_blank" class="keylink">vcD4NCjxwcmUgY2xhc3M9"brush:java;"> #import @interface ViewController : UIViewController{ //定義一個警告對話框視圖對象 UIAlertView * _alertView; //等待提示對象 //當下載，或者加載比較大的文件時，可以顯示此控件，處於提示等待狀態 UIActivityIndicatorView * _activityIndicator; } @property(retain,nonatomic) UIAlertView * alertView; @property(retain,nonatomic) UIActivityIndicatorView * activityIndicator; @end

實現：

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

//實現屬性和成員變量的同步
@synthesize alertView =_alertView;
@synthesize activityIndicator=_activityIndicator;

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    for(int i=0;i<2;i++){
        UIButton * btn =[UIButton buttonWithType:UIButtonTypeRoundedRect];
        btn.frame = CGRectMake(100, 100+100*i, 100, 40);
        if(i==0){
            [btn setTitle:@"警告對話框" forState:UIControlStateNormal];
        }
        else if(i==1){
            [btn setTitle:@"等待指示器" forState:UIControlStateNormal];
        }

        btn.tag = 101+i;

        [btn addTarget:self action:@selector(pressBtn:) forControlEvents:UIControlEventTouchUpInside];

        [self.view addSubview:btn];
    }
}

-(void) pressBtn:(UIButton*) btn{
    //警告對話框創建
    //p1:對話框標題
    //p2:提示信息
    //p3:處理按鈕事件的代理對象
    //p4:取消按鈕的文字,默認的索引為0；
    //p5:其他按鈕文字 ** otherButtonTitles:@"確定", nil]; 只有取消和確定按鈕是橫向排開
    // otherButtonTitles:@"確定",@"確定1",@"確定2", nil];這樣子就會全部縱向排開，索引依次是1，2，3.
    //p6:...:添加其他按鈕
    //nil:表示按鈕添加結束
    if(btn.tag==101){
        _alertView = [[UIAlertView alloc]initWithTitle:@"警告"
                                               message:@"你的手機電量過低，請保存數據"
                                              delegate:self
                                     cancelButtonTitle:@"取消"
                                     otherButtonTitles:@"確定", nil];

        //顯示對話框
        [_alertView show];
    }
    //創建等待提示器，大伙都叫他菊花
    else if(btn.tag==102){
        //創建等待提示器，寬高不可變更
        _activityIndicator =[[UIActivityIndicatorView alloc]initWithFrame:CGRectMake(100, 300, 80, 80)];

        //設定提示的風格:小灰，小白，大白
        _activityIndicator.activityIndicatorViewStyle =UIActivityIndicatorViewStyleGray;//小灰

//        _activityIndicator.activityIndicatorViewStyle=UIActivityIndicatorViewStyleWhite;//小白
//        
//        _activityIndicator.activityIndicatorViewStyle=UIActivityIndicatorViewStyleWhiteLarge;//大白

//        self.view.backgroundColor=[UIColor blueColor];

        [self.view addSubview:_activityIndicator];

        //啟動動畫並顯示
        [_activityIndicator startAnimating];

        //停止等待動畫並隱藏
//        [_activityIndicator stopAnimating];

    }
}

//當點擊對話框的按鈕時，調用此函數
//p1:對話框對象本身
//p2:按鈕的索引
-(void) alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex{
    NSLog(@"index=%ld\n",buttonIndex);
}

//對話框即將消失，此函數被調用
-(void) alertView:(UIAlertView *)alertView willDismissWithButtonIndex:(NSInteger)buttonIndex{
    NSLog(@"即將消失！");
}

//對話框已經消失時，調用此函數
-(void) alertView:(UIAlertView *)alertView didDismissWithButtonIndex:(NSInteger)buttonIndex{
    NSLog(@"已經消失");
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end