进度显示例子学习

Cocoa Touch提供用于通知用户等待进程完成的类：
1、UIActivityIndicatorView:提供一个旋转的圆，通知用户等待，不提供具体信息
2、UIProgressView:显示进度条，量化工作量（时间）
3、UIProgressHUD:不量化工作，但显示工作状态或描绘进度。注意此类不在标准的SDK中

针对以上三类，分别用代码来演示应用
1\

#define INDICATOR_VIEW    999

@interface HelloController : UIViewController
{
    BOOL progressShowing;
}
@end

@implementation HelloController
- (void) performAction
{
    UIActivityIndicatorView *activityIndicator = (UIActivityIndicatorView *)[self.view viewWithTag:INDICATOR_VIEW];
    if (progressShowing) [activityIndicator stopAnimating]; else [activityIndicator startAnimating];
    progressShowing = !progressShowing;
}

- (id) init
{
    if (self = [super init]) self.title = @"Hello World";
    return self;
}

- (void)loadView
{
    UIView *contentView = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]];
    self.view = contentView;
    contentView.backgroundColor = [UIColor whiteColor];
    [contentView release];
   
    self.navigationItem.rightBarButtonItem = [[[UIBarButtonItem alloc]
                                               initWithTitle:@"Do It"
                                               style:UIBarButtonItemStylePlain
                                               target:self
                                               action:@selector(performAction)] autorelease];
   
    // Add the progress indicator but do not start it
    progressShowing = NO;
    UIActivityIndicatorView *activityIndicator = [[UIActivityIndicatorView alloc] initWithFrame:CGRectMake(0.0f, 0.0f, 32.0f, 32.0f)];
    [activityIndicator setCenter:CGPointMake(160.0f, 208.0f)];
    [activityIndicator setActivityIndicatorViewStyle:UIActivityIndicatorViewStyleGray];
    activityIndicator.tag = INDICATOR_VIEW;
    [contentView addSubview:activityIndicator];
    [activityIndicator release];
}
@end

代码中个人觉得关键的地方在：progressShowing和activityIndicator.tag = INDICATOR_VIEW;[contentView addSubview:activityIndicator];


2\

扩展UIActionSheet函数

@interface UIActionSheet (extended)
- (void) setNumberOfRows: (NSInteger) rows;
- (void) setMessage: (NSString *)message;
@end

//Timer事件处理

- (void) incrementBar: (id) timer
{
    amountDone += 1.0f;
    UIProgressView *progbar = (UIProgressView *)[self.baseSheet viewWithTag:PROGRESS_BAR];
    [progbar setProgress: (amountDone / 20.0)];
    if (amountDone > 20.0)
    {
        [self.baseSheet dismissWithClickedButtonIndex:0 animated:YES];
        [timer invalidate];
    }
}

//呈现视图

- (void) presentSheet
{
   
    if (!self.baseSheet) {
        baseSheet = [[UIActionSheet alloc]
                     initWithTitle:@"Please Wait"
                     delegate:self
                     cancelButtonTitle:nil
                     destructiveButtonTitle: nil
                     otherButtonTitles: nil];
        [baseSheet setNumberOfRows:5];
        [baseSheet setMessage:@"Updating Internal Databases"];
       
        UIProgressView *progbar = [[UIProgressView alloc] initWithFrame:CGRectMake(50.0f, 70.0f, 220.0f, 90.0f)];
        progbar.tag = PROGRESS_BAR;
        [progbar setProgressViewStyle: UIProgressViewStyleDefault];
        [baseSheet addSubview:progbar];
        [progbar release];
    }
   
    UIProgressView *progbar = (UIProgressView *)[self.view viewWithTag:PROGRESS_BAR];
    [progbar setProgress:(amountDone = 0.0f)];
    [NSTimer scheduledTimerWithTimeInterval: 0.5 target: self selector: @selector(incrementBar:) userInfo: nil repeats: YES];
    [baseSheet showInView:self.view];
}

注意释放函数

- (void) dealloc
{
    //释放baseSheet
    if (self.baseSheet) [self.baseSheet release];
    [super dealloc];
}

此例Timer来定时更新进度条状态
为了显示进度状态，特用了UIActionSheet来处理

在XCode4上执行，看不到应有的效果~~杯具中，看后续怎么处理

另外，
        [baseSheet setNumberOfRows:5];
        [baseSheet setMessage:@"Updating Internal Databases"];
没有执行应有的效果~~~

3\
声明已存在的类

- (void) dealloc
{
    //释放baseSheet
    if (self.baseSheet) [self.baseSheet release];
    [super dealloc];
}

控制器中部分代码

- (void) killHUD: (id) aHUD
{
    [aHUD show:NO];
    [aHUD release];
}
- (void) presentSheet
{
    id HUD = [[UIProgressHUD alloc] initWithWindow:[self.view superview]];
    [HUD setText:@"Downloading File. Please wait."];
    [HUD show:YES];
   
    [self performSelector:@selector(killHUD:) withObject:HUD afterDelay:5.0];
}

类学习：

UIActivityIndicatorView类

The UIActivityIndicatorView class creates and manages an indicator showing the indeterminate progress of a task.

UIActivityIndicatorView类创建并管理指示器，此指示器用于显示当前任务的进度。

方法：
    – initWithActivityIndicatorStyle:
    – startAnimating
    – stopAnimating
    – isAnimating
   
属性：
      hidesWhenStopped表示当动画结束后此视图是否隐藏

      activityIndicatorViewStyle指示器视图样式

UIProgressView类

方法：
    – initWithProgressViewStyle:

属性：
    progress：进度，float，0.0-1.0
    progressViewStyle：进度视图样式
   
未公开：
UIProgressHUD类   

UIActionSheet的部分函数：
- (void) setNumberOfRows: (NSInteger) rows;
- (void) setMessage: (NSString *)message;