如何以編程方式創建UI元素

Question

我希望能夠在每次用戶點擊按鈕時在單獨的UIViewController中創建新的UI元素（UIProgressView欄）。

我怎麼會去這樣做呢？

Answer 1

以編程方式創建一個UIProgressView，它是簡單地使用alloc和初始化，設置幀的事情，添加一個子視圖，就像這樣：

//.h 

#import <UIKit/UIKit.h> 

@interface ExampleViewController : UIViewController { 

    //create the ivar 
    UIProgressView *_progressView; 

} 
/*I like to back up my iVars with properties. If you aren't using ARC, use retain instead of strong*/ 
@property (nonatomic, strong) UIProgressView *progressView; 

@end 

//.m 

@implementation 
@synthesize progressView = _progressView; 

-(void)viewDidLoad { 
    /* it isn't necessary to create the progressView here, after all you could call this code from any method you wanted to and it would still work*/ 
    //allocate and initialize the progressView with the bar style 
    self.progressView = [[UIProgressView alloc]initWithProgressViewStyle:UIProgressViewStyleBar]; 
    //add the progressView to our main view. 
    [self.view addSubview: self.progressView]; 
    //if you ever want to remove it, call [self.progressView removeFromSuperView]; 

} 

Answer 2

閱讀本指南https://developer.apple.com/library/ios/#DOCUMENTATION/WindowsViews/Conceptual/ViewPG_iPhoneOS/CreatingViews/CreatingViews.html

大部分的UI元素的創建是這樣的：

UIView *view = [[UIView alloc] initWithFrame:CGRect]; 
// set the property of the view here 
// ... 

// finally add your view 
[ViewController.view addSubView:view];