这里介绍一下网友开源的MBProgressHUD类，实现等待框，

一、网上下载  MBProgessHUD 类文件，直接导入到工程即可

二、示例分析

在我的工程中示例如下：

1）在ShowImageViewController.h头文件代码如下：

#import <UIKit/UIKit.h>

#import "MBProgressHUD.h"

@interface ShowImageViewController : UIViewController <MBProgressHUDDelegate>{

NSString         *_picUrlString;

UIImageView      *_imageView;

MBProgressHUD    *_progressHUD;

}

@property (nonatomic, copy) NSString           *picUrlString;

@property (nonatomic, retain) IBOutlet         UIImageView *imageView;

@property (nonatomic, retain) MBProgressHUD    *progressHUD;

//请求图片资源

-(void)imageResourceRequest;

//显示图片信息

-(void)displayImage:(UIImage *)image;

- (IBAction)dismissModealView:(id)sender;

-(void)removeModalView;

@end

2）在ShowImageViewController.m实现文件代码如下：

#import "ShowImageViewController.h"

#import <QuartzCore/QuartzCore.h>

@implementation ShowImageViewController

@synthesize picUrlString = _picUrlString;

@synthesize imageView = _imageView;

@synthesize progressHUD = _progressHUD;

- (void)viewDidLoad

{

[super viewDidLoad];

// Do any additional setup after loading the view from its nib.

self.view.backgroundColor = [UIColor grayColor];

self.view.alpha = 0.8;

//设置图片为圆角

self.imageView.backgroundColor = [UIColor clearColor];

self.imageView.layer.borderColor = [UIColor lightGrayColor].CGColor;

self.imageView.layer.borderWidth = 5.0;

self.imageView.layer.masksToBounds = YES;

self.imageView.layer.cornerRadius = 10.0;

}

-(void)viewWillAppear:(BOOL)animated

{

[super viewWillAppear:animated];

//当进入视图时，重新设置imageView

[self.imageView setImage:nil];

[self.imageView setFrame:CGRectMake(160, 200, 0, 0)];

//显示加载等待框

self.progressHUD = [[MBProgressHUD alloc] initWithView:self.view];

[self.view addSubview:self.progressHUD];

[self.view bringSubviewToFront:self.progressHUD];

self.progressHUD.delegate = self;

self.progressHUD.labelText = @"加载中...";

[self.progressHUD show:YES];

//开启线程，请求图片资源

[NSThread detachNewThreadSelector:@selector(imageResourceRequest) toTarget:self withObject:nil];

}

//请求图片资源

-(void)imageResourceRequest

{

NSAutoreleasePool   *pool = [[NSAutoreleasePool alloc] init];

//根据网络数据，获得到image资源

NSData  *data = [[NSData alloc] initWithContentsOfURL:[NSURL URLWithString:self.picUrlString]];

UIImage *image = [[UIImage alloc] initWithData:data];

[data release];

//回到主线程，显示图片信息

[self performSelectorOnMainThread:@selector(displayImage:) withObject:image waitUntilDone:NO];

[image release];

[pool release];

}

//显示图片信息

-(void)displayImage:(UIImage *)image

{

//若self.progressHUD为真，则将self.progressHUD移除，设为nil

if (self.progressHUD){

[self.progressHUD removeFromSuperview];

[self.progressHUD release];

self.progressHUD = nil;

}

//图片慢慢放大动画效果

[self.imageView setImage:image];

[UIView beginAnimations:nil context:nil];

[UIView setAnimationDuration:0.5];

[self.imageView setFrame:CGRectMake(40, 100, 240, 160)];

[UIView commitAnimations];

}

- (void)viewDidUnload

{

[self setImageView:nil];

[super viewDidUnload];

// Release any retained subviews of the main view.

// e.g. self.myOutlet = nil;

}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation

{

// Return YES for supported orientations

return (interfaceOrientation == UIInterfaceOrientationPortrait);

}

- (IBAction)dismissModealView:(id)sender {

//设置定时器，当动画结束时，子视图从父视图中移除

[NSTimer scheduledTimerWithTimeInterval:0.5 target:self selector:@selector(removeModalView) userInfo:nil repeats:NO];

[UIView beginAnimations:nil context:nil];

[UIView setAnimationDuration:0.5];

[self.imageView setFrame:CGRectMake(160, 200, 0, 0)];

[UIView commitAnimations];

}

-(void)removeModalView

{

[self.view removeFromSuperview];

}

#pragma mark -

#pragma mark MBProgressHUDDelegate methods

- (void)hudWasHidden:(MBProgressHUD *)hud {

NSLog(@"Hud: %@", hud);

// Remove HUD from screen when the HUD was hidded

[self.progressHUD removeFromSuperview];

[self.progressHUD release];

self.progressHUD = nil;

}

- (void)dealloc

{

[_picUrlString release];

[_imageView release];

[super dealloc];

}

@end

三、效果展示

四、总结

利用MBProgressHUD实现加载等待框，视觉效果大大提高