iphone - 如何以编程方式创建 UI 元素

Question

每次用户点击按钮时，我都希望能够在单独的 UIViewController 中创建新的 UI 元素(UIProgressView 栏)。

我该怎么做？

Answer 1

要以编程方式创建 UIProgressView，只需使用 alloc 和 init、设置框架并添加 subview ，如下所示:

//.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];

}